Subject: Re: [MOBILE-IP] Mobile IP Routing Implementation Issue

From: Vipul Gupta <[email-masked]>
Date: Fri, 13 Oct 2000 10:02:05 -0700

Gavin,

    When the mobile node is away from its home network, you need to
  remove the routing table entry for the home network (100.100.100.0).
  The only route entries you should have are:

    - an entry that says the FA (default router) is directly reachable
      from the MN's network interface
    - traffic for all hosts must be directed to the default router (FA).

  This way, the MN's IP forwarding code will not try to ARP for
  100.100.100.207. Instead, the packet will be sent to the FA.

  You don't mention what operating system you are using but at least
  Solaris and Linux allow routing tables to be set as above.

  vipul

> Hi All,
>
> I am researching and implementing MobileIP as defined in RFC2002, October
> 1996 and have a question.
>
> My configuration within a private network is as follows:
> Mobile Host: IP address 100.100.101.239
> Home Agent: IP address 100.100.101.233
> Foreign Agent: IP Address 10.0.0.2
> (all subnet masks are 255.255.255.0)
>
> The Mobile Host visits the Foreign Agent network and registers the Care of
> Address (10.0.0.2) with the Home Agent. Once registration has completed I
> ping the Mobile Host from a machine on its Home Network (100.100.100.207).
> The ping request reaches the Mobile Host succesfully, at which point the
> TCP/IP stack attempts a broadcast ARP Request to determine the MAC address
> of 100.100.101.207, which it believes to be on the same network, this fails
> so the ping reply is never generated.
>
> The section in RFC 2002 on Mobile Host Datagram Routing (4.2.1) states that
> a default router should be selected for the foreign network. If I do this
> and set the deafult router to be 10.0.0.1 (router between the two networks)
> then it still does generates an ARP request for 100.100.101.207. I believe
> this is because the TCP/IP stack doesnt recognise the router, 10.0.0.1, as
> being on the same network as its IP Address, 100.100.101.239, so does not
> consider it for sending the ping reply to.
>
> Can anyone explain what I might be doing wrong?
>
> Thanks in Advance,
>
> Gavin Button

---

From: Gavin Button <[email-masked]>
Date: Mon, 16 Oct 2000 08:59:27 +0100

Vipul,

        Thanks for your comments.

        I am developing under Windows 2000 and there doesn't seem to be any obvious
way of manipulating the router tables from the device driver level. I was
considering answering the ARP message myself with the address of the default
router.

        With regards to your comments about what the router tables should be set
to.

- In the network configuration I have set up, the FA is not actually the
default router for the network, does it have to be?
- Windows 2000 doesn't seem to allow you to set up routes which are
incorrect, i.e. Sending packets to a router with an IP Address that is not
on the same network.

Regards,

Gavin Button

-----Original Message-----
From: IP Routing for Wireless/Mobile Hosts (mobile-ip)
[mailto:[email-masked]]On Behalf Of Vipul Gupta
Sent: 13 October 2000 18:02
To: [email-masked]
Subject: Re: [MOBILE-IP] Mobile IP Routing Implementation Issue

  Gavin,

  vipul