Subject: RE: Doubt

From: basila <[email-masked]>
Date: Sat, 23 May 98 10:06:00 PDT

Acee,

Thanks for the immediate response.

As you said, VRRP is for providing transparent gateway for the hosts. But   
still this is the VRRP operational issue which we have to take care while   
deploying VRRP routers in the network.

Let me put forward my doubt in a better way.

In the following topology (same depicted in my previous mail):

                 +-----+
                 |     |
          (IP C) | H3  |
                 |     |
                 +--+--+
                    |
                    | Network C
   -----------------+------------------
                    |
                    |
                 +--+--+
                 |     |
                 | VR3 |
                 |     |
                 +-----+
                   --
                 /    \
            /----       ----\
           |       IP        |
            \____       ____/
                 \    /
                   --
    +--+--+                    +--+--+
    |     |                    |     |
    | VR1 |                    | VR2 |
    |     |                    |     |
    +--+--+                    +--+--+
       |                          |
       |                          |
   ----+--+--------------------+--+----
Network A |                    | Network B
          |                    |
       +--+--+              +--+--+
       |     |              |     |
(IP A) | H1  |              | H2  | (IP B)
       |     |              |     |
       +-----+              +-----+

Assumptions:
    VR1, VR2 and VR3 are Virtual routers connected by IP network.
    H1, H2 and H3 are hosts connected through Virtual routers
    VR1 is master for Network A
    VR2 is backing up VR1
    Active FTP session is going on between H1 and H3 through VR1<->VR3

In the abovementioned topology, VR1 becomes backup from master because of   
coming up of VR2, which has higher priority. Therefore there is a   
forwarding responsibility for "Network A" from VR1 to VR2 (i.e.. VR1   
becoming backup and VR2 becoming master). But this is not known to VR3.   
VR3 will still sends the data to VR1 which is intended H1 (Network A).   
VR1 is in backup state now so it will discard the data. To avoid this,   
there should be some way of informing VR3 that the data intended H1   
(Network A) should be sent to VR2.

Now coming back to my doubt, how do I inform VR3 about the forwarding   
responsibility change between VR1 and VR2?

In other words, how do I inform VR3 that the data intended for H1   
(Network A) should be sent to VR2 instead of VR1?

Hope my doubts are somewhat clear now.

Looking for your reply.

Regards,

Basil

 -----Original Message-----
From: Acee Lindem [SMTP:[email-masked]]
Sent: Friday, May 22, 1998 10:12 AM
To: basila
Cc: 'vrrp'
Subject: Re: Doubt

basila wrote:
   Pruned
     o
     o
>
>
>    Problem Description:
>     Let's consider a scenario where there is a active FTP session
>     between H1 and H3 through Virtual routers VR1 <-> VR3. When
>     virtual router VR1 is down, its forwarding responsibility
>     should be taken over by VR2. So the FTP session between H1 and
>     H3 should be through VR2<->VR3.
>
>     But the information about forwarding responsibility changeover
>     between VR1 and VR2 is not available VR3. Since this information
>     is not available with VR3, it will route the packets to VR1
>     where the packets will get dropped, as it is in backup state now.
>     To avoid this situation, the information about the forwarding
>     responsibility changeover between VR1 and VR2 should be made
>     available to VR3.

Anton,

VRRP's primary goal is to provide transparent default gateway backup for
hosts.  It is not meant to be routing protocol - use RIP or OSPF between
routers VR1, VR2, VR3. Let's take this a step further - if the VR1
connection to VR3 goes down but it is still active on the LAN with
the H1, you will need to run an IGP (e.g., RIP or OSPF) on the LAN
with VRRP so that VR1 has the correct routes and can send redirects
to hosts using it as a default gateway.

 --
Acee