Subject: VRRP IP addresses

From: "Juan D. S�nchez" <[email-masked]>
Date: Wed, 05 Aug 1998 07:53:39 -0700

Hi,

I have a question regarding one of the scenarios shown in the VRRP-MIB.
I took the original figure and added specific IP addresses.  If I 
interpreted the example correctly, the figure shown below would be 
a valid scenario.

The question is about the secondary address on the Left-Router (LR).
If the LR goes down, and the RR becomes the Master for VR1, then
the RR will have to forward traffic destined to the 120 net
(traffic that would be received by the RR on interfaces not shown
below).  

However, interface-y is not configured with an IP address in the
120 net.  It may be possible that the only thing that the RR
knew about the 120 subnet, came from routing advertisements 
transmitted by the LR, which is now down.  

Using the MIB as a reference, the RR would not even know about 
the subnet mask of the 120 net.  

On the RR, should VRRP add an entry in the routing table for the 120 
net (with a default mask - class A, B, C) ?

Should interface-y HAVE to have a secondary IP address (on the 120 net), 
for the configuration of VR1 to be valid ?

I wonder if this case was discussed in the working group meetings,
and if an informal agreement about how to deal with this scenario
was reached.  

Thanks for any comments on this issue,
Juan D. Sanchez
YAGO Systems

    VRRP Config for Left-Router    VRRP Config for Right-Router 
    ---------------------------    --------------------------- 
      VR1 = (interface-x             VR1 = (interface-y        
             IP-1:100.0.0.1                 IP-1:100.0.0.1     
             IP-2:120.0.0.1)                IP-2:120.0.0.1)    
                                                               
      VR2 = (interface-x             VR2 = (interface-y        
             IP-1:100.0.0.2)                IP-1:100.0.0.2)    
 
                       VRID=1       VRID=2
                      +-----+      +-----+
                      | MR1 |      | MR2 |
                      |  &  |      |  &  |
                      | BR2 |      | BR1 |
                      +-----+      +-----+
  100.0.0.1              *            *
           > Interface-x |            | Interface-y = 100.0.0.2
  120.0.0.1              |            |
                         |            |
                         |            |
       -----+------------+------+-----+---------+----+
            ^                   ^               ^      
            |                   |               |      
            |                   |               |      
         +--+--+             +--+--+         +--+--+   
         |  H1 |             |  H2 |         |  H3 |   
         +-----+             +-----+         +-----+   
       default-rtr          default-rtr     default-rtr
        100.0.0.1            100.0.0.2       120.0.0.1