Subject: Clarification in changing the router id dynamically!!

From: kamatchi soundaram <[email-masked]>
Date: Thu, 3 Jul 2003 12:44:04 -0700

Hi,

  If the router id of the router R1 is changed on the fly (dynamically),
what factor triggers the adjacent router R2 connected to R1 via point to
point link, to generate the new Router LSA???

 From the RFC i could infer that R1 will flush all his self originated lsas
when it's router lsa has been changed.
  But i couldn't find, how the R2 triggered to generate the new router lsa
with the changed router id as is neighbor id in its router lsa??

Thanks in advance,
Kamatchi.

---

From: Acee Lindem <[email-masked]>
Date: Fri, 4 Jul 2003 21:25:48 -0400

> with the changed router id as is neighbor id in its router lsa??

Kamatchi,

Actually, since neighbors are identified by router ID on P2P links (as per
RFC 2338 section 8.2), R2 shouldn't recognize R1 with the new router ID and
should bring down the old adjacency with R1 and form a new one. A more
interesting question is what would happen on a broadcast or NBMA network
(where neighbors are identified by source address).
This case isn't explicitly handled by RFC 2328 and there is some variance
between implementations. At a minimum, the DR must recognize the change
in router ID and originate a new network LSA. I found that one popular
implementation required the router with the router ID change to bring its
adjacencies down (by sending a hello w/o any neighbor IDs) in order to
interoperate.

Thanks,
Acee

--
Acee

---

From: kamatchi soundaram <[email-masked]>
Date: Tue, 8 Jul 2003 11:51:37 -0700

Hi Acee,

----- Original Message -----
From: "Acee Lindem" <[email-masked]>
To: <[email-masked]>
Sent: Friday, July 04, 2003 6:25 PM
Subject: Re: Clarification in changing the router id dynamically!!

> adjacencies down (by sending a hello w/o any neighbor IDs) in order to

Does it mean that the R1 (router whose Id has got changed), should reset
it's NSM with all its neighbor to down/init state and then send hello
without any neighbor ids??

  Since, R1 need to flush all it's self originated lsas before to bring down
the adjacency and restart again, there needs some ample amount of time to
flood and flush the lsas in the routing domain (atleast with the neighbor).
So, i cannot send the hello packet (without any neighbors) immedietly after
the sending out the max age lsas (to flush the self originated lsas).

 Because if i do that, then there is a chance that before the self
originated lsas are completely flushed out or sent from R1, the NSM may
reverted to down state. Which will basically prevent the complete flushing
of self oringinated lsas . . correct??

 My question is how can be the time between the flushing the lsas and
hello's sent without the neighbor ids determined???

 Since, if there is no significant amount left between the lsa flushing and
new hello without neighbor id, then the entire system will be in bad
condition.

Thanks,
Kamatchi.

---

From: Acee Lindem <[email-masked]>
Date: Tue, 8 Jul 2003 16:00:38 -0400

kamatchi soundaram wrote:
>>> From the RFC i could infer that R1 will flush all his self originated
>>
> lsas
>
>>>  But i couldn't find, how the R2 triggered to generate the new router
>>
> lsa
>
>>RFC 2338 section 8.2), R2 shouldn't recognize R1 with the new router ID
>
> and
>

Hi Kamatchi,

> the sending out the max age lsas (to flush the self originated lsas).

I purge self-originated LSAs before sending the empty hello. I do both
before the router ID change. I do not add the self-originated LSAs to
any retransmission lists and I do not wait for acknowledgements. Some
implementations just let their old LSAs time out and without any
strong complaints.

> of self oringinated lsas . . correct??

Only if your Link State Update packet is dropped.

--
Acee