IP Prefix Advertisement in
Ethernet VPN (EVPN)Nokia777 E. Middlefield RoadMountain ViewCA94043United States of Americajorge.rabadan@nokia.comNokiawim.henderickx@nokia.comJuniperjdrake@juniper.netJuniperwlin@juniper.netCiscosajassi@cisco.comBESS WorkgroupRT5RT-5Type-5Interface-lessInterface-ful
The BGP MPLS-based Ethernet VPN (EVPN) (RFC 7432) mechanism provides a
flexible control plane that allows intra-subnet connectivity in an
MPLS and/or Network Virtualization Overlay (NVO) (RFC 7365) network.
In some networks, there is also a need for dynamic and efficient
inter-subnet connectivity across Tenant Systems and end devices that
can be physical or virtual and do not necessarily participate in
dynamic routing protocols. This document defines a new EVPN route
type for the advertisement of IP prefixes and explains some use-case
examples where this new route type is used.Introduction provides a framework for Data Center (DC) Network Virtualization
over Layer 3 and specifies that the Network Virtualization Edge (NVE) devices must provide Layer 2 and Layer 3 virtualized network services in
multi-tenant DCs. discusses the use of EVPN as the technology of
choice to provide Layer 2 or intra-subnet services in these DCs. This
document, along with , specifies the use of EVPN for Layer 3 or inter-subnet connectivity services. defines some
fairly common inter-subnet forwarding scenarios where Tenant Systems (TSs) can exchange
packets with TSs located in remote subnets. In order to achieve this,
describes how Media Access
Control (MAC) and IPs encoded in TS RT-2 routes are not only used to populate MAC Virtual Routing and Forwarding (MAC-VRF) and
overlay Address Resolution Protocol (ARP) tables but also IP-VRF tables with the encoded TS host routes
(/32 or /128). In some cases, EVPN may advertise IP prefixes and therefore
provide aggregation in the IP-VRF tables, as opposed to propagating
individual host routes. This document complements the scenarios described
in and defines
how EVPN may be used to advertise IP prefixes. Interoperability between
EVPN and Layer 3 Virtual Private Network (VPN) IP Prefix routes is out of the
scope of this document. describes the
inter-subnet connectivity requirements in DCs. explains why a new EVPN route
type is required for IP prefix advertisements. Sections , , and will
describe this route type and how it is used in some specific use
cases.Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 when, and only when, they appear in all
capitals, as shown here.
AC:
Attachment Circuit
ARP:
Address Resolution Protocol
BD:
Broadcast Domain. As per , an EVI consists
of a single BD or multiple BDs. In case of VLAN-bundle and VLAN-based
service models (see ), a BD is equivalent to
an EVI. In case of a VLAN-aware bundle service model, an EVI contains
multiple BDs. Also, in this document, "BD" and "subnet" are equivalent
terms.
BD Route Target:
Refers to the broadcast-domain-assigned Route Target . In case of a VLAN-aware
bundle service model, all the BD instances in the MAC-VRF share the
same Route Target.
BT:
Bridge Table. The instantiation of a BD in a
MAC-VRF, as per .
CE:
Customer Edge
DA:
Destination Address
DGW:
Data Center Gateway
Ethernet A-D Route:
Ethernet Auto-Discovery (A-D)
route, as per .
Ethernet NVO Tunnel:
Refers to Network Virtualization
Overlay tunnels with Ethernet payload. Examples of this type of
tunnel are VXLAN or GENEVE.
EVI:
EVPN Instance spanning the NVE/PE devices that are
participating on that EVPN, as per .
EVPN:
Ethernet VPN, as per .
GENEVE:
Generic Network Virtualization Encapsulation, as per .
GRE:
Generic Routing Encapsulation
GW IP:
Gateway IP address
IPL:
IP Prefix Length
IP NVO Tunnel:
Refers to Network Virtualization
Overlay tunnels with IP payload (no MAC header in the payload).
IP-VRF:
A Virtual Routing and Forwarding table for IP
routes on an NVE/PE. The IP routes could be populated by EVPN and
IP-VPN address families. An IP-VRF is also an instantiation of a Layer
3 VPN in an NVE/PE.
IRB:
Integrated Routing and Bridging interface. It
connects an IP-VRF to a BD (or subnet).
MAC:
Media Access Control
MAC-VRF:
A Virtual Routing and Forwarding table for
MAC addresses on an NVE/PE, as per . A MAC-VRF is also an instantiation of an EVI in an
NVE/PE.
ML:
MAC Address Length
ND:
Neighbor Discovery
NVE:
Network Virtualization Edge
NVO:
Network Virtualization Overlay
PE:
Provider Edge
RT-2:
EVPN Route Type 2, i.e., MAC/IP Advertisement
route, as defined in .
RT-5:
EVPN Route Type 5, i.e., IP Prefix route, as
defined in .
SBD:
Supplementary Broadcast Domain. A BD that does not
have any ACs, only IRB interfaces, and is used to provide
connectivity among all the IP-VRFs of the tenant. The SBD is only
required in IP-VRF-to-IP-VRF use cases (see ).
SN:
Subnet
TS:
Tenant System
VA:
Virtual Appliance
VM:
Virtual Machine
VNI:
Virtual Network Identifier. As in , the
term is used as a representation of a 24-bit NVO instance identifier,
with the understanding that "VNI" will refer to a VXLAN Network
Identifier in VXLAN, or a Virtual Network Identifier in GENEVE,
etc., unless it is stated otherwise.
VSID:
Virtual Subnet Identifier
VTEP:
VXLAN Termination End Point, as per .
VXLAN:
Virtual eXtensible Local Area Network, as per .
This document also assumes familiarity with the terminology of
, , and .Problem Statement
This section describes the inter-subnet connectivity requirements in
DCs and why a specific route type to advertise IP prefixes
is needed.Inter-Subnet Connectivity Requirements in Data Centers is used as the control plane for an NVO solution in DCs, where NVE devices can be located in hypervisors or
Top-of-Rack (ToR) switches, as described in .
The following considerations apply to TSs that are
physical or virtual systems identified by MAC (and possibly IP addresses)
and are connected to BDs by Attachment Circuits:
The Tenant Systems may be VMs that generate
traffic from their own MAC and IP.
The Tenant Systems may be VA entities that
forward traffic to/from IP addresses of different end devices sitting
behind them.
These VAs can be firewalls, load balancers, NAT devices, other
appliances, or virtual gateways with virtual routing instances.
These VAs do not necessarily participate in dynamic routing
protocols and hence rely on the EVPN NVEs to advertise the routes on
their behalf.
In all these cases, the VA will forward traffic to other TSs using
its own source MAC, but the source IP will be the one associated with the
end device sitting behind the VA or a translated IP address (part of a public
NAT pool) if the VA is performing NAT.
Note that the same IP address and endpoint could exist behind two
of these TSs. One example of this would be certain appliance
resiliency mechanisms, where a virtual IP or floating IP can be owned
by one of the two VAs running the resiliency protocol (the Master
VA). The Virtual Router Redundancy Protocol (VRRP) is one
particular example of this. Another example is multihomed subnets,
i.e., the same subnet is connected to two VAs.
Although these VAs provide IP connectivity to VMs and the subnets
behind them, they do not always have their own IP interface connected
to the EVPN NVE; Layer 2 firewalls are examples of VAs not
supporting IP interfaces.
illustrates some of the examples described above.DC Inter-subnet Use CasesWhere:NVE1, NVE2, NVE3, NVE4, NVE5, DGW1, and DGW2 share the same BD for a
particular tenant. BD-10 is comprised of the collection of BD
instances defined in all the NVEs. All the hosts connected to BD-10
belong to the same IP subnet. The hosts connected to BD-10 are listed
below:
TS1 is a VM that generates/receives traffic to/from IP1, where IP1
belongs to the BD-10 subnet.
TS2 and TS3 are VAs that send/receive traffic
to/from the subnets and hosts sitting behind them (SN1, SN2, SN3, IP4, and
IP5). Their IP addresses (IP2 and IP3) belong to the BD-10 subnet, and they
can also generate/receive traffic. When these VAs receive packets destined
to their own MAC addresses (M2 and M3), they will route the packets to the
proper subnet or host. These VAs do not support routing protocols to
advertise the subnets connected to them and can move to a different server
and NVE when the cloud management system decides to do so. These VAs may
also support redundancy mechanisms for some subnets, similar to VRRP, where
a floating IP is owned by the Master VA and only the Master VA forwards
traffic to a given subnet. For example, vIP23 in is a floating IP that
can be owned by TS2 or TS3 depending on which system is the Master. Only
the Master will forward traffic to SN1.
Integrated Routing and Bridging interfaces IRB1, IRB2, and IRB3 have
their own IP addresses that belong to the BD-10 subnet too. These IRB
interfaces connect the BD-10 subnet to Virtual Routing and Forwarding
(IP-VRF) instances that can route the traffic to other subnets for the same
tenant (within the DC or at the other end of the WAN).
TS4 is a Layer 2 VA that provides connectivity to subnets SN5, SN6, and
SN7 but does not have an IP address itself in the BD-10. TS4 is connected
to a port on NVE5 that is assigned to Ethernet Segment Identifier 4 (ESI4).
For a BD to which an ingress NVE is attached, "Overlay Index" is
defined as an identifier that the ingress EVPN NVE requires in order
to forward packets to a subnet or host in a remote subnet. As an
example, vIP23 () is an Overlay Index that any NVE attached
to BD-10 needs to know in order to forward packets to SN1. The IRB3 IP
address is an Overlay Index required to get to SN4, and ESI4 is an Overlay Index needed to forward
traffic to SN5. In other words, the Overlay Index is a next hop in
the overlay address space that can be an IP address, a MAC address, or
an ESI. When advertised along with an IP prefix, the Overlay Index
requires a recursive resolution to find out the egress NVE to which the
EVPN packets need to be sent.
All the DC use cases in require inter-subnet
forwarding; therefore, the individual host routes and subnets:
must be advertised from the NVEs (since VAs and VMs do not
participate in dynamic routing protocols) and
may be associated with an Overlay Index that can be a VA IP address,
a floating IP address, a MAC address, or an ESI. The Overlay Index is
further discussed in .
The Need for the EVPN IP Prefix Route defines a MAC/IP Advertisement route (also
referred to as "RT-2") where a MAC
address can be advertised together with an IP address length and IP
address (IP). While a variable IP address length might have been used
to indicate the presence of an IP prefix in a route type 2, there are
several specific use cases in which using this route type to deliver
IP prefixes is not suitable.
One example of such use cases is the "floating IP" example described
in . In this example, it is
necessary to decouple the advertisement of the prefixes from the advertisement of a MAC address
of either M2 or M3; otherwise, the solution gets highly inefficient
and does not scale.
For example, if 1,000 prefixes are advertised from M2 (using RT-2)
and the floating IP owner changes from M2 to M3, 1,000 routes would
be withdrawn by M2 and readvertised by M3. However, if a
separate route type is used, 1,000 routes can be advertised as
associated with the floating IP address (vIP23), and only one RT-2 can be used for
advertising the ownership of the floating IP, i.e., vIP23 and M2 in
the route type 2. When the floating IP owner changes from M2 to M3, a
single RT-2 withdrawal/update is required to indicate the change. The
remote DGW will not change any of the 1,000 prefixes associated with
vIP23 but will only update the ARP resolution entry for vIP23 (now
pointing at M3).
An EVPN route (type 5) for the advertisement of IP prefixes is
described in this document. This new route type has a differentiated
role from the RT-2 route and addresses the inter-subnet connectivity
scenarios for DCs (or NVO-based
networks in general) described in
this document. Using this new RT-5, an IP prefix may be advertised
along with an Overlay Index, which can be a GW IP address, a MAC, or an
ESI. The IP prefix may also be advertised without an Overlay Index, in which case the BGP next hop will
point at the egress NVE, Area Border Router (ABR), or ASBR, and the MAC in the EVPN Router's MAC
Extended Community will provide the inner MAC destination address to
be used. As discussed throughout the document, the EVPN RT-2 does not
meet the requirements for all the DC use cases; therefore, this EVPN
route type 5 is required.
The EVPN route type 5 decouples the IP prefix advertisements from the
MAC/IP Advertisement routes in EVPN. Hence:
The clean and clear advertisements of IPv4 or IPv6 prefixes
in a Network Layer Reachability Information (NLRI) message without
MAC addresses are allowed.
Since the route type is different from the MAC/IP Advertisement
route, the current procedures described in do not need to
be modified.
A flexible implementation is allowed where the prefix can be linked to
different types of Overlay/Underlay Indexes: overlay IP addresses,
overlay MAC addresses, overlay ESIs, underlay BGP next hops, etc.
An EVPN implementation not requiring IP prefixes can simply discard
them by looking at the route type value.
The following sections describe how EVPN is extended with a route
type for the advertisement of IP prefixes and how this route is used
to address the inter-subnet connectivity requirements existing in the
DC.The BGP EVPN IP Prefix Route The BGP EVPN NLRI as defined in is shown below:BGP EVPN NLRI
+-----------------------------------+
| Route Type (1 octet) |
+-----------------------------------+
| Length (1 octet) |
+-----------------------------------+
| Route Type specific (variable) |
+-----------------------------------+
This document defines an additional route type (RT-5) in the IANA
"EVPN Route Types" registry to be used for the
advertisement of EVPN routes using IP prefixes:
Value:
5
Description:
IP Prefix
According to , a node that doesn't recognize the
route type 5 (RT-5) will ignore it. Therefore, an NVE following this
document can still be attached to a BD where an NVE ignoring RT-5s is
attached. Regular procedures described in would apply in that case for both
NVEs. In case two or more NVEs are attached to different BDs of the same
tenant, they MUST support the RT-5 for the proper inter-subnet forwarding
operation of the tenant.
The detailed encoding of this route and associated procedures are
described in the following sections.IP Prefix Route Encoding
An IP Prefix route type for IPv4 has the Length field set to 34 and
consists of the following fields:EVPN IP Prefix Route NLRI for IPv4
+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| IP Prefix Length (1 octet, 0 to 32) |
+---------------------------------------+
| IP Prefix (4 octets) |
+---------------------------------------+
| GW IP Address (4 octets) |
+---------------------------------------+
| MPLS Label (3 octets) |
+---------------------------------------+
An IP Prefix route type for IPv6 has the Length field set to 58 and
consists of the following fields:EVPN IP Prefix Route NLRI for IPv6
+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| IP Prefix Length (1 octet, 0 to 128) |
+---------------------------------------+
| IP Prefix (16 octets) |
+---------------------------------------+
| GW IP Address (16 octets) |
+---------------------------------------+
| MPLS Label (3 octets) |
+---------------------------------------+
Where:
The Length field of the BGP EVPN NLRI for an EVPN IP Prefix route
MUST be either 34 (if IPv4 addresses are carried) or 58 (if IPv6
addresses are carried). The IP prefix and gateway IP address MUST
be from the same IP address family.
The Route Distinguisher (RD) and Ethernet Tag ID MUST be used as
defined in and . In particular, the RD is unique
per MAC-VRF (or IP-VRF). The MPLS Label field is set to either an
MPLS label or a VNI, as described in for other EVPN route
types.
The Ethernet Segment Identifier MUST be a non-zero 10-octet
identifier if the ESI is used as an Overlay Index (see the
definition of "Overlay Index" in ). It MUST be all bytes zero otherwise. The ESI format is described in .
The IP prefix length can be set to a value between 0 and 32 (bits)
for IPv4 and between 0 and 128 for IPv6, and it specifies the number
of bits in the prefix. The value MUST NOT be greater than 128.
The IP prefix is a 4- or 16-octet field (IPv4 or IPv6).
The GW IP Address field is a 4- or 16-octet field (IPv4 or
IPv6) and will encode a valid IP address as an Overlay Index for
the IP prefixes. The GW IP field MUST be all bytes zero if it is
not used as an Overlay Index. Refer to for the
definition and use of the Overlay Index.
The MPLS Label field is encoded as 3 octets, where the high-order
20 bits contain the label value, as per . When sending,
the label value SHOULD be zero if a recursive resolution based on
an Overlay Index is used. If the received MPLS label value is zero,
the route MUST contain an Overlay Index, and the ingress NVE/PE MUST
perform a recursive resolution to find the egress NVE/PE. If the received
label is zero and the route does not contain an Overlay Index, it
MUST be "treat as withdraw" .
The RD, Ethernet Tag ID, IP prefix length, and IP prefix are part of
the route key used by BGP to compare routes. The rest of the fields
are not part of the route key.
An IP Prefix route MAY be sent along with an EVPN Router's MAC Extended Community
(defined in ) to
carry the MAC address that is used as the Overlay Index. Note that the MAC
address may be that of a TS.
As described in , certain data combinations in a received
route would imply a treat-as-withdraw handling of the route
.Overlay Indexes and Recursive Lookup Resolution
RT-5 routes support recursive lookup resolution through the use of
Overlay Indexes as follows:
An Overlay Index can be an ESI or IP address in the address space
of the tenant or MAC address, and it is used by an NVE as the
next hop for a given IP prefix. An Overlay Index always needs a
recursive route resolution on the NVE/PE that installs the RT-5 into
one of its IP-VRFs so that the NVE knows to which egress NVE/PE it
needs to forward the packets. It is important to note that recursive
resolution of the Overlay Index applies upon installation into an
IP-VRF and not upon BGP propagation (for instance, on an ASBR).
Also, as a result of the recursive resolution, the egress NVE/PE is
not necessarily the same NVE that originated the RT-5.
The Overlay Index is indicated along with the RT-5 in the ESI
field, GW IP field, or EVPN Router's MAC Extended Community, depending on
whether the IP prefix next hop is an ESI, an IP address, or a MAC address
in the tenant space. The Overlay Index for a given IP prefix is set
by local policy at the NVE that originates an RT-5 for that IP
prefix (typically managed by the cloud management system).
In order to enable the recursive lookup resolution at the ingress
NVE, an NVE that is a possible egress NVE for a given Overlay Index
must originate a route advertising itself as the BGP next hop on the
path to the system denoted by the Overlay Index. For instance:
If an NVE receives an RT-5 that specifies an Overlay Index, the
NVE cannot use the RT-5 in its IP-VRF unless (or until) it can
recursively resolve the Overlay Index.
If the RT-5 specifies an ESI as the Overlay Index, a recursive
resolution can only be done if the NVE has received and installed an
RT-1 (auto-discovery per EVI) route specifying that ESI.
If the RT-5 specifies a GW IP address as the Overlay Index,
a recursive resolution can only be done if the NVE has received and
installed an RT-2 (MAC/IP Advertisement route) specifying that IP address in the
IP Address field of its NLRI.
If the RT-5 specifies a MAC address as the Overlay Index,
a recursive resolution can only be done if the NVE has received and
installed an RT-2 (MAC/IP Advertisement route) specifying that MAC address in the
MAC Address field of its NLRI.
Note that the RT-1 or RT-2 routes needed for the
recursive resolution may arrive before or after the given RT-5
route.
Irrespective of the recursive resolution, if there is no IGP or BGP
route to the BGP next hop of an RT-5, BGP MUST NOT install the RT-5
even if the Overlay Index can be resolved.
The ESI and GW IP fields may both be zero at the same time.
However, they MUST NOT both be non-zero at the same time. A route
containing a non-zero GW IP and a non-zero ESI (at the same time)
SHOULD be treat as withdraw .
If either the ESI or the GW IP are non-zero, then the non-zero one is
the Overlay Index, regardless of whether the EVPN Router's MAC Extended
Community is present or the value of the label. In case the GW IP is
the Overlay Index (hence, ESI is zero), the EVPN Router's MAC Extended
Community is ignored if present.
A route where ESI, GW IP, MAC, and Label are all zero at the same
time SHOULD be treat as withdraw.
The indirection provided by the Overlay Index and its recursive
lookup resolution is required to achieve fast convergence in case of
a failure of the object represented by the Overlay Index (see the
example described in ). shows the different RT-5 field combinations allowed by this
specification and what Overlay Index must be used by the receiving
NVE/PE in each case. Cases where there is no Overlay Index are
indicated as "None" in . If there is no Overlay Index, the
receiving NVE/PE will not perform any recursive resolution, and the
actual next hop is given by the RT-5's BGP next hop.
RT-5 Fields and Indicated Overlay Index
ESI
GW IP
MAC*
Label
Overlay Index
Non-Zero
Zero
Zero
Don't Care
ESI
Non-Zero
Zero
Non-Zero
Don't Care
ESI
Zero
Non-Zero
Zero
Don't Care
GW IP
Zero
Zero
Non-Zero
Zero
MAC
Zero
Zero
Non-Zero
Non-Zero
MAC or None**
Zero
Zero
Zero
Non-Zero
None***
Table Notes:
*
MAC with "Zero" value means no EVPN Router's MAC Extended Community is
present along with the RT-5. "Non-Zero" indicates that the extended
community is present and carries a valid MAC address. The encoding of
a MAC address MUST be the 6-octet MAC address specified by . Examples
of invalid MAC addresses are broadcast or multicast MAC
addresses. The route MUST be treat as withdraw in case of an invalid
MAC address. The presence of the EVPN Router's MAC Extended Community
alone is not enough to indicate the use of the MAC address as the
Overlay Index since the extended community can be used for other
purposes.
**
In this case, the Overlay Index may be the RT-5's MAC address or
"None", depending on the local policy of the receiving NVE/PE. Note
that the advertising NVE/PE that sets the Overlay Index SHOULD
advertise an RT-2 for the MAC Overlay Index if there are receiving
NVE/PEs configured to use the MAC as the Overlay Index. This case in
is used in the IP-VRF-to-IP-VRF
implementations described in Sections and . The support of a MAC Overlay Index in this model is
OPTIONAL.
***
The Overlay Index is "None". This is a special case used for
IP-VRF-to-IP-VRF where the NVE/PEs are connected by IP NVO tunnels as
opposed to Ethernet NVO tunnels.
If the combination of ESI, GW IP, MAC, and Label in the receiving RT-5
is different than the combinations shown in , the router will
process the route as per the rules described at the beginning of this
section (). shows the different inter-subnet use cases described in this
document and the corresponding coding of the Overlay Index in the
route type 5 (RT-5).
Use Cases and Overlay Indexes for Recursive Resolution
Section
Use Case
Overlay Index in the RT-5
TS IP address
GW IP
Floating IP address
GW IP
"Bump-in-the-wire"
ESI or MAC
IP-VRF-to-IP-VRF
GW IP, MAC, or None
The above use cases are representative of the different Overlay
Indexes supported by the RT-5 (GW IP, ESI, MAC, or None).Overlay Index Use Cases This
section describes some use cases for the Overlay Index types used with
the IP Prefix route.
Although the examples use IPv4 prefixes and
subnets, the descriptions of the RT-5 are valid for the same cases
with IPv6, except that IP Prefixes, IPL, and GW IP are replaced by the
corresponding IPv6 values.TS IP Address Overlay Index Use Case illustrates an example of inter-subnet forwarding for
subnets sitting behind VAs (on TS2 and TS3).TS IP Address Use Case
An example of inter-subnet forwarding between subnet SN1, which uses
a 24-bit IP prefix (written as SN1/24 in the future), and a subnet
sitting in the WAN is described below. NVE2, NVE3, DGW1, and DGW2 are
running BGP EVPN. TS2 and TS3 do not participate in dynamic routing
protocols, and they only have a static route to forward the traffic
to the WAN. SN1/24 is dual-homed to NVE2 and NVE3.
In this case, a GW IP is used as an Overlay Index. Although a
different Overlay Index type could have been used, this use case
assumes that the operator knows the VA's IP addresses beforehand,
whereas the VA's MAC address is unknown and the VA's ESI is zero.
Because of this, the GW IP is the suitable Overlay Index to be used
with the RT-5s. The NVEs know the GW IP to be used for a given prefix
by policy.
NVE2 advertises the following BGP routes on behalf of TS2:
Route type 2 (MAC/IP Advertisement route) containing: ML = 48 (MAC address length),
M = M2 (MAC address), IPL = 32 (IP prefix length), IP = IP2, and BGP
Encapsulation Extended Community with the corresponding tunnel type. The
MAC and IP addresses may be learned via ARP snooping.
Route type 5 (IP Prefix route) containing: IPL = 24, IP = SN1,
ESI = 0, and GW
IP address = IP2. The prefix and GW IP are learned by policy.
Similarly, NVE3 advertises the following BGP routes on behalf of TS3:
Route type 2 (MAC/IP Advertisement route) containing: ML = 48, M = M3, IPL = 32, IP = IP3
(and BGP Encapsulation Extended Community).
Route type 5 (IP Prefix route) containing: IPL = 24, IP = SN1,
ESI = 0, and GW IP address = IP3.
DGW1 and DGW2 import both received routes based on the Route Targets:
Based on the BD-10 Route Target in DGW1 and DGW2, the MAC/IP Advertisement route
is imported, and M2 is added to the BD-10 along with its corresponding
tunnel information. For instance, if VXLAN is used, the VTEP will be
derived from the MAC/IP Advertisement route BGP next hop and VNI from the MPLS Label1
field. M2/IP2 is added to the ARP table. Similarly, M3 is added to
BD-10, and M3/IP3 is added to the ARP table.
Based on the BD-10 Route Target in DGW1 and DGW2, the IP Prefix
route is also imported, and SN1/24 is added to the IP-VRF with Overlay
Index IP2 pointing at the local BD-10. In this example, it is assumed
that the RT-5 from NVE2 is preferred over the RT-5 from NVE3. If both
routes were equally preferable and ECMP enabled, SN1/24 would also be
added to the routing table with Overlay Index IP3.
When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
A destination IP lookup is performed on the DGW1 IP-VRF table, and Overlay Index = IP2 is found. Since IP2 is an Overlay Index, a
recursive route resolution is required for IP2.
IP2 is resolved to M2 in the ARP table, and M2 is resolved to the
tunnel information given by the BD FIB (e.g., remote VTEP and VNI for
the VXLAN case).
The IP packet destined to IPx is encapsulated with:
Inner source MAC = IRB1 MAC.
Inner destination MAC = M2.
Tunnel information provided by the BD (VNI, VTEP IPs, and MACs for
the VXLAN case).
When the packet arrives at NVE2:
Based on the tunnel information (VNI for the VXLAN case), the BD-10
context is identified for a MAC lookup.
Encapsulation is stripped off and, based on a MAC lookup
(assuming MAC forwarding on the egress NVE), the packet is
forwarded to TS2, where it will be properly routed.
Should TS2 move from NVE2 to NVE3, MAC Mobility procedures will be applied
to the MAC route M2/IP2, as defined in . Route type 5
prefixes are not subject to MAC Mobility procedures; hence, no changes in the
DGW IP-VRF table will occur for TS2 mobility -- i.e., all the prefixes will still
be pointing at IP2 as the Overlay Index. There is an indirection for, e.g., SN1/24,
which still points at Overlay Index IP2 in the routing table, but IP2 will be
simply resolved to a different tunnel based on the outcome of the MAC
Mobility procedures for the MAC/IP Advertisement route M2/IP2.
Note that in the opposite direction, TS2 will send traffic based on
its static-route next-hop information (IRB1 and/or IRB2), and regular
EVPN procedures will be applied.Floating IP Overlay Index Use Case
Sometimes TSs work in active/standby mode where an
upstream floating IP owned by the active TS is used as the
Overlay Index to get to some subnets behind the TS. This redundancy mode,
already introduced in Sections and , is illustrated in .Floating IP Overlay Index for Redundant TS
In this use case, a GW IP is used as an Overlay Index for the same
reasons as in . However, this GW IP is a floating IP that belongs
to the active TS. Assuming TS2 is the active TS and owns vIP23:
NVE2 advertises the following BGP routes for TS2:
Route type 2 (MAC/IP Advertisement route) containing: ML = 48, M = M2, IPL = 32, and
IP = vIP23 (as well as BGP Encapsulation Extended Community). The MAC and IP
addresses may be learned via ARP snooping.
Route type 5 (IP Prefix route) containing: IPL = 24, IP = SN1,
ESI = 0, and GW
IP address = vIP23. The prefix and GW IP are learned by policy.
NVE3 advertises the following BGP route for TS3 (it does not advertise an
RT-2 for M3/vIP23):
Route type 5 (IP Prefix route) containing: IPL = 24, IP = SN1,
ESI = 0, and GW
IP address = vIP23. The prefix and GW IP are learned by policy.
DGW1 and DGW2 import both received routes based on the Route Target:
M2 is added to the BD-10 FIB along with its corresponding tunnel
information. For the VXLAN use case, the VTEP will be derived from the
MAC/IP Advertisement route BGP next hop and VNI from the VNI field. M2/vIP23 is added
to the ARP table.
SN1/24 is added to the IP-VRF in DGW1 and DGW2 with Overlay Index
vIP23 pointing at M2 in the local BD-10.
When DGW1 receives a packet from the WAN with destination IPx, where IPx
belongs to SN1/24:
A destination IP lookup is performed on the DGW1 IP-VRF table,
and Overlay Index = vIP23 is found. Since vIP23 is an Overlay Index, a
recursive route resolution for vIP23 is required.
vIP23 is resolved to M2 in the ARP table, and M2 is resolved to the
tunnel information given by the BD (remote VTEP and VNI for the VXLAN
case).
The IP packet destined to IPx is encapsulated with:
Inner source MAC = IRB1 MAC.
Inner destination MAC = M2.
Tunnel information provided by the BD FIB (VNI, VTEP IPs, and MACs
for the VXLAN case).
When the packet arrives at NVE2:
Based on the tunnel information (VNI for the VXLAN case), the BD-10
context is identified for a MAC lookup.
Encapsulation is stripped off and, based on a MAC lookup (assuming
MAC forwarding on the egress NVE), the packet is forwarded to TS2,
where it will be properly routed.
When the redundancy protocol running between TS2 and TS3 appoints TS3 as
the new active TS for SN1, TS3 will now own the floating vIP23 and will signal
this new ownership using a gratuitous ARP REPLY message (explained in ) or similar. Upon receiving the new owner's notification,
NVE3 will issue a route type 2 for M3/vIP23, and NVE2 will withdraw the RT-2
for M2/vIP23. DGW1 and DGW2 will update their ARP tables with the new MAC
resolving the floating IP. No changes are made in the IP-VRF table.
Bump-in-the-Wire Use Case illustrates an example of inter-subnet forwarding for an IP
Prefix route that carries subnet SN1. In this use case, TS2 and TS3
are Layer 2 VA devices without any IP addresses that can be included as
an Overlay Index in the GW IP field of the IP Prefix route. Their MAC
addresses are M2 and M3, respectively, and are connected to BD-10. Note
that IRB1 and IRB2 (in DGW1 and DGW2, respectively) have IP addresses
in a subnet different than SN1.Bump-in-the-Wire Use Case
Since TS2 and TS3 cannot participate in any dynamic routing
protocol and neither has an IP address assigned, there are two potential
Overlay Index types that can be used when advertising SN1:
an ESI, i.e., ESI23, that can be provisioned on the attachment
ports of NVE2 and NVE3, as shown in or
the VA's MAC address, which can be added to NVE2 and NVE3 by
policy.
The advantage of using an ESI as the Overlay Index as opposed to the VA's MAC
address is that the forwarding to the egress NVE can be done purely based
on the state of the AC in the Ethernet segment (notified by the Ethernet A-D per EVI
route), and all the EVPN multihoming redundancy mechanisms can be
reused. For instance, the mass withdrawal mechanism described in for fast
failure detection and propagation can be used. It is assumed per this section that
an ESI Overlay Index is used in this use case, but this use case does not preclude the
use of the VA's MAC address as an Overlay Index. If a MAC is used as
the Overlay Index, the control plane must follow the procedures described in
.
The model supports VA redundancy in a similar way to the one
described in for the floating IP Overlay Index use case,
except that it uses the EVPN Ethernet A-D per EVI route instead of
the MAC advertisement route to advertise the location of the Overlay
Index. The procedure is explained below:
Assuming TS2 is the active TS in ESI23, NVE2 advertises the
following BGP routes:
Route type 1 (Ethernet A-D route for BD-10) containing: ESI = ESI23 and
the corresponding tunnel information (VNI field), as well as the BGP
Encapsulation Extended Community as per .
Route type 5 (IP Prefix route) containing: IPL = 24, IP = SN1,
ESI = ESI23, and GW IP address = 0. The EVPN Router's MAC Extended Community defined in
is added and carries the MAC address (M2)
associated with the TS behind which SN1 sits. M2 may be learned by policy; however, the
MAC in the Extended Community is preferred if sent with the route.
NVE3 advertises the following BGP route for TS3 (no AD per EVI route is
advertised):
Route type 5 (IP Prefix route) containing: IPL = 24, IP = SN1,
ESI = 23, and GW IP address = 0. The EVPN Router's MAC Extended Community is added and
carries the MAC address (M3) associated with the TS behind which SN1
sits. M3 may be learned by policy; however, the MAC in the Extended
Community is preferred if sent with the route.
DGW1 and DGW2 import the received routes based on the Route Target:
The tunnel information to get to ESI23 is installed in DGW1 and
DGW2. For the VXLAN use case, the VTEP will be derived from the
Ethernet A-D route BGP next hop and VNI from the VNI/VSID field (see
).
The RT-5 coming from the NVE that advertised the RT-1 is
selected, and SN1/24 is added to the IP-VRF in DGW1 and DGW2 with Overlay Index
ESI23 and MAC = M2.
When DGW1 receives a packet from the WAN with destination IPx, where IPx
belongs to SN1/24:
A destination IP lookup is performed on the DGW1 IP-VRF table, and Overlay Index = ESI23 is found. Since ESI23 is an Overlay
Index, a recursive route resolution is required to find the egress NVE
where ESI23 resides.
The IP packet destined to IPx is encapsulated with:
Inner source MAC = IRB1 MAC.
Inner destination MAC = M2 (this MAC will be obtained from the
EVPN Router's MAC Extended Community received along with the RT-5 for
SN1). Note that the EVPN Router's MAC Extended Community is used in this
case to carry the TS's MAC address, as opposed to the MAC
address of the NVE/PE.
Tunnel information for the NVO tunnel is provided by the Ethernet
A-D route per EVI for ESI23 (VNI and VTEP IP for the VXLAN
case).
When the packet arrives at NVE2:
Based on the tunnel demultiplexer information (VNI for the VXLAN
case), the BD-10 context is identified for a MAC lookup (assuming a MAC-based disposition model ), or the VNI may directly identify
the egress interface (for an MPLS-based disposition model, which in this
context is a VNI-based disposition model).
Encapsulation is stripped off and, based on a MAC lookup (assuming MAC
forwarding on the egress NVE) or a VNI lookup (in case of VNI
forwarding), the packet is forwarded to TS2, where it will be forwarded
to SN1.
If the redundancy protocol running between TS2 and TS3 follows an
active/standby model and there is a failure, TS3 is appointed as the new active
TS for SN1. TS3 will now own the connectivity to SN1 and will signal this new
ownership. Upon receiving the new owner's notification, NVE3's AC will become
active and issue a route type 1 for ESI23, whereas NVE2 will withdraw its
Ethernet A-D route for ESI23. DGW1 and DGW2 will update their tunnel
information to resolve ESI23. The inner destination MAC will be changed to
M3.
IP-VRF-to-IP-VRF Model
This use case is similar to the scenario described in ; however, the new
requirement here is the advertisement of IP prefixes as opposed to
only host routes.
In the examples described in Sections , , and , the BD
instance can connect IRB interfaces and any other Tenant Systems
connected to it. EVPN provides connectivity for:
Traffic destined to the IRB or TS IP interfaces, as well as
Traffic destined to IP subnets sitting behind the TS, e.g., SN1
or SN2.
In order to provide connectivity for (1), MAC/IP Advertisement routes (RT-2) are
needed so that IRB or TS MACs and IPs can be distributed.
Connectivity type (2) is accomplished by the exchange of IP Prefix
routes (RT-5) for IPs and subnets sitting behind certain Overlay
Indexes, e.g., GW IP, ESI, or TS MAC.
In some cases, IP Prefix routes may be advertised for subnets and IPs
sitting behind an IRB. This use case is referred to as the
"IP-VRF-to-IP-VRF" model. defines an asymmetric IRB model and a symmetric
IRB model based on the required lookups at the ingress and egress
NVE. The asymmetric model requires an IP lookup and a MAC lookup at
the ingress NVE, whereas only a MAC lookup is needed at the egress
NVE; the symmetric model requires IP and MAC lookups at both the ingress
and egress NVE. From that perspective, the IP-VRF-to-IP-VRF use case
described in this section is a symmetric IRB model.
Note that in an IP-VRF-to-IP-VRF scenario, out of the many subnets that a
tenant may have, it may be the case that only a few are attached to a given
IP-VRF of the NVE/PE. In order to provide inter-subnet connectivity among the
set of NVE/PEs where the tenant is connected, a new SBD is created on all
of them if a recursive resolution is needed. This SBD is instantiated as a
regular BD (with no ACs) in each NVE/PE and has an IRB interface that
connects the SBD to the IP-VRF. The IRB interface's IP or MAC address is
used as the Overlay Index for a recursive resolution.
Depending on the existence and characteristics of the SBD and IRB
interfaces for the IP-VRFs, there are three different IP-VRF-to-IP-VRF
scenarios identified and described in this document:
Interface-less model: no SBD and no Overlay Indexes required.
Interface-ful with an SBD IRB model: requires SBD as well as GW IP addresses as Overlay Indexes.
Interface-ful with an unnumbered SBD IRB model: requires SBD as well as MAC addresses as Overlay Indexes.
Inter-subnet IP multicast is outside the scope of this document.Interface-less IP-VRF-to-IP-VRF Model depicts the Interface-less IP-VRF-to-IP-VRF model.Interface-less IP-VRF-to-IP-VRF ModelIn this case:
The NVEs and DGWs must provide connectivity between hosts in SN1,
SN2, and IP1 and hosts sitting at the other end of the WAN -- for example,
H1. It is assumed that the DGWs import/export IP and/or VPN-IP routes
to/from the WAN.
The IP-VRF instances in the NVE/DGWs are directly connected through
NVO tunnels, and no IRBs and/or BD instances are instantiated to
connect the IP-VRFs.
The solution must provide Layer 3 connectivity among the IP-VRFs
for Ethernet NVO tunnels -- for instance, VXLAN or GENEVE.
The solution may provide Layer 3 connectivity among the IP-VRFs for
IP NVO tunnels -- for example, GENEVE (with IP payload).
In order to meet the above requirements, the EVPN route type 5 will be used
to advertise the IP prefixes, along with the EVPN Router's MAC Extended
Community as defined in if the advertising
NVE/DGW uses Ethernet NVO tunnels. Each NVE/DGW will advertise an RT-5 for
each of its prefixes with the following fields:
RD as per .
Ethernet Tag ID = 0.
IP prefix length and IP address, as explained in the previous
sections.
GW IP address = 0.
ESI = 0.
MPLS label or VNI corresponding to the IP-VRF.
Each RT-5 will be sent with a Route Target identifying the tenant
(IP-VRF) and may be sent with two BGP extended communities:
The first one is the BGP Encapsulation Extended Community, as per
, identifying the tunnel type.
The second one is the EVPN Router's MAC Extended Community, as per
, containing the MAC address associated with the NVE advertising the
route. This MAC address identifies the NVE/DGW and MAY be reused for
all the IP-VRFs in the NVE. The EVPN Router's MAC Extended Community must
be sent if the route is associated with an Ethernet NVO tunnel -- for
instance, VXLAN. If the route is associated with an IP NVO tunnel -- for
instance, GENEVE with an IP payload -- the EVPN Router's MAC Extended Community
should not be sent.
The following example illustrates the procedure to advertise and
forward packets to SN1/24 (IPv4 prefix advertised from NVE1):
NVE1 advertises the following BGP route:
Route type 5 (IP Prefix route) containing:
IPL = 24, IP = SN1, Label = 10.
GW IP = set to 0.
BGP Encapsulation Extended
Community .
EVPN Router's MAC Extended Community that contains M1.
Route Target identifying the tenant (IP-VRF).
DGW1 imports the received routes from NVE1:
DGW1 installs SN1/24 in the IP-VRF identified by the RT-5
Route Target.
Since GW IP = ESI = 0, the label is a non-zero value, and the
local policy indicates this interface-less model, DGW1, will use
the label and next hop of the RT-5, as well as the MAC address
conveyed in the EVPN Router's MAC Extended Community (as the inner
destination MAC address) to set up the forwarding state and
later encapsulate the routed IP packets.
When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
A destination IP lookup is performed on the DGW1 IP-VRF
table. The lookup yields SN1/24.
Since the RT-5 for SN1/24 had a GW IP = ESI = 0, a non-zero
label, and a next hop, and since the model is interface-less, DGW1 will
not need a recursive lookup to resolve the route.
The IP packet destined to IPx is encapsulated with: inner source MAC = DGW1 MAC, inner destination MAC = M1, outer source
IP (tunnel source IP) = DGW1 IP, and outer destination IP (tunnel
destination IP) = NVE1 IP. The source and inner destination MAC
addresses are not needed if IP NVO tunnels are used.
When the packet arrives at NVE1:
NVE1 will identify the IP-VRF for an IP lookup based on the
label (the inner destination MAC is not needed to identify the
IP-VRF).
An IP lookup is performed in the routing context, where SN1
turns out to be a local subnet associated with BD-2. A subsequent
lookup in the ARP table and the BD FIB will provide the
forwarding information for the packet in BD-2.
The model described above is called an "interface-less" model since the
IP-VRFs are connected directly through tunnels, and they don't require
those tunnels to be terminated in SBDs instead, as in Sections or .Interface-ful IP-VRF-to-IP-VRF with SBD IRB depicts the Interface-ful IP-VRF-to-IP-VRF with SBD IRB model.Interface-ful with SBD IRB ModelIn this model:
As in , the NVEs and DGWs must provide connectivity
between hosts in SN1, SN2, and IP10 and in hosts sitting at the other end
of the WAN.
However, the NVE/DGWs are now connected through Ethernet NVO
tunnels terminated in the SBD instance. The IP-VRFs use IRB
interfaces for their connectivity to the SBD.
Each SBD IRB has an IP and a MAC address, where the IP address
must be reachable from other NVEs or DGWs.
The SBD is attached to all the NVE/DGWs in the tenant domain BDs.
The solution must provide Layer 3 connectivity for Ethernet NVO
tunnels -- for instance, VXLAN or GENEVE (with Ethernet payload).
EVPN type 5 routes will be used to advertise the IP prefixes, whereas
EVPN RT-2 routes will advertise the MAC/IP addresses of each SBD IRB
interface. Each NVE/DGW will advertise an RT-5 for each of its
prefixes with the following fields:
RD as per .
Ethernet Tag ID = 0.
IP prefix length and IP address, as explained in the previous
sections.
GW IP address = IRB-IP of the SBD (this is the Overlay Index that
will be used for the recursive route resolution).
ESI = 0.
Label value should be zero since the RT-5 route requires a
recursive lookup resolution to an RT-2 route. It is ignored on
reception, and the MPLS label or VNI from
the RT-2's MPLS Label1 field is used when forwarding packets.
Each RT-5 will be sent with a Route Target identifying the tenant
(IP-VRF). The EVPN Router's MAC Extended Community should not be sent in
this case.
The following example illustrates the procedure to advertise and
forward packets to SN1/24 (IPv4 prefix advertised from NVE1):
NVE1 advertises the following BGP routes:
Route type 5 (IP Prefix route) containing:
IPL = 24, IP = SN1, Label = SHOULD be set to 0.
GW IP = IP1 (SBD IRB's IP).
Route Target identifying the tenant (IP-VRF).
Route type 2 (MAC/IP Advertisement route for the SBD IRB) containing:
ML = 48, M = M1, IPL = 32, IP = IP1, Label = 10.
A BGP Encapsulation Extended Community .
Route Target identifying the SBD. This Route Target may be the
same as the one used with the RT-5.
DGW1 imports the received routes from NVE1:
DGW1 installs SN1/24 in the IP-VRF identified by the RT-5 Route
Target.
Since GW IP is different from zero, the GW IP (IP1) will be
used as the Overlay Index for the recursive route resolution to
the RT-2 carrying IP1.
When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
A destination IP lookup is performed on the DGW1 IP-VRF
table. The lookup yields SN1/24, which is associated with
the Overlay Index IP1. The forwarding information is derived from
the RT-2 received for IP1.
The IP packet destined to IPx is encapsulated with: inner source MAC = M3, inner destination MAC = M1, outer source IP
(source VTEP) = DGW1 IP, and outer destination IP (destination VTEP)
= NVE1 IP.
When the packet arrives at NVE1:
NVE1 will identify the IP-VRF for an IP lookup based on the
label and the inner MAC DA.
An IP lookup is performed in the routing context, where SN1
turns out to be a local subnet associated with BD-2. A subsequent
lookup in the ARP table and the BD FIB will provide the
forwarding information for the packet in BD-2.
The model described above is called an "interface-ful with SBD IRB" model because the tunnels connecting the DGWs and NVEs need to be
terminated into the SBD. The SBD is connected to the IP-VRFs via SBD
IRB interfaces, and that allows the recursive resolution of RT-5s to
GW IP addresses.Interface-ful IP-VRF-to-IP-VRF with Unnumbered SBD IRB depicts the Interface-ful IP-VRF-to-IP-VRF with unnumbered SBD IRB model. Note that this model is similar to the one described in , only
without IP addresses on the SBD IRB interfaces.Interface-ful with Unnumbered SBD IRB ModelIn this model:
As in Sections and , the NVEs and DGWs must provide
connectivity between hosts in SN1, SN2, and IP1 and in hosts sitting at the
other end of the WAN.
As in , the NVE/DGWs are connected through Ethernet
NVO tunnels terminated in the SBD instance. The IP-VRFs use IRB
interfaces for their connectivity to the SBD.
However, each SBD IRB has a MAC address only and no IP address
(which is why the model refers to an "unnumbered" SBD IRB). In this
model, there is no need to have IP reachability to the SBD IRB
interfaces themselves, and there is a requirement to limit the number
of IP addresses used.
As in , the SBD is composed of all the NVE/DGW BDs of
the tenant that need inter-subnet forwarding.
As in , the solution must provide Layer 3 connectivity
for Ethernet NVO tunnels -- for instance, VXLAN or GENEVE (with Ethernet
payload).
This model will also make use of the RT-5 recursive resolution. EVPN
type 5 routes will advertise the IP prefixes along with the EVPN Router's
MAC Extended Community used for the recursive lookup, whereas EVPN
RT-2 routes will advertise the MAC addresses of each SBD IRB
interface (this time without an IP).
Each NVE/DGW will advertise an RT-5 for each of its prefixes with the
same fields as described in , except:
GW IP address = set to 0.
Each RT-5 will be sent with a Route Target identifying the tenant
(IP-VRF) and the EVPN Router's MAC Extended Community containing the MAC
address associated with the SBD IRB interface. This MAC address may be
reused for all the IP-VRFs in the NVE.
The example is similar to the one in :
NVE1 advertises the following BGP routes:
Route type 5 (IP Prefix route) containing the same values as
in the example in , except:
GW IP = SHOULD be set to 0.
EVPN Router's MAC Extended Community containing M1 (this will be used
for the recursive lookup to an RT-2).
Route type 2 (MAC route for the SBD IRB) with the same values
as in , except:
ML = 48, M = M1, IPL = 0, Label = 10.
DGW1 imports the received routes from NVE1:
DGW1 installs SN1/24 in the IP-VRF identified by the RT-5
Route Target.
The MAC contained in the EVPN Router's MAC Extended Community sent
along with the RT-5 (M1) will be used as the Overlay Index for the
recursive route resolution to the RT-2 carrying M1.
When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
A destination IP lookup is performed on the DGW1 IP-VRF
table. The lookup yields SN1/24, which is associated with
the Overlay Index M1. The forwarding information is derived from
the RT-2 received for M1.
The IP packet destined to IPx is encapsulated with: inner source MAC = M3, inner destination MAC = M1, outer source IP
(source VTEP) = DGW1 IP, and outer destination IP (destination VTEP)
= NVE1 IP.
When the packet arrives at NVE1:
NVE1 will identify the IP-VRF for an IP lookup based on the
label and the inner MAC DA.
An IP lookup is performed in the routing context, where SN1
turns out to be a local subnet associated with BD-2. A subsequent
lookup in the ARP table and the BD FIB will provide the
forwarding information for the packet in BD-2.
The model described above is called an "interface-ful with unnumbered SBD
IRB" model (as in ) but without the SBD IRB having an IP address.Security Considerations
This document provides a set of procedures to achieve inter-subnet
forwarding across NVEs or PEs attached to a group of BDs that belong
to the same tenant (or VPN). The security considerations discussed in
apply to the intra-subnet forwarding or communication
within each of those BDs. In addition, the security considerations in
should also be understood, since this document and
may be used in similar applications.
Contrary to , this document does not describe PE/CE route
distribution techniques but rather considers the CEs as TSs or VAs
that do not run dynamic routing protocols. This can be considered a
security advantage, since dynamic routing protocols can be blocked on
the NVE/PE ACs, not allowing the tenant to interact with the
infrastructure's dynamic routing protocols.
In this document, the RT-5 may use a regular BGP next hop for its
resolution or an Overlay Index that requires a recursive resolution
to a different EVPN route (an RT-2 or an RT-1). In the latter case,
it is worth noting that any action that ends up filtering or
modifying the RT-2 or RT-1 routes used to convey the Overlay Indexes
will modify the resolution of the RT-5 and therefore the forwarding
of packets to the remote subnet.IANA Considerations
IANA has registered value 5 in the "EVPN Route Types" registry
defined by as follows:
Value
Description
Reference
5
IP Prefix
RFC 9136
ReferencesNormative ReferencesIntegrated Routing and Bridging in Ethernet VPN (EVPN)EVPN Route TypesIANAInformative ReferencesIEEE Standard for Local and Metropolitan Area Networks -- Bridges and Bridged NetworksIEEEAcknowledgments
The authors would like to thank , , and for
their valuable feedback and contributions.
and also helped improve this document with their feedback. Special thanks to for his detailed
review, which really helped improve the readability and clarify the
concepts. We also thank for his thorough review.Contributors
In addition to the authors listed on the front page, the following
coauthors have also contributed to this document: