🚀 go-pugleaf

We have a problem where the arp cache gets corrupted on a router
and the ethernet address does not correspond to the correct IP address.
When this has happened, it is usually the ethernet address of one of the
cisco ethernets providing the link to the other router. Our setup has
three routers, call them A, B, and C. Each router is connected via ethernet
to the other two. A picture showing the subnet assignments
would be the following:



                        |-----|
                        |_____| machine on subnet 100 that should be on 50
                           |
                           |
                           |
                           |
                   13.1    A   12,1
                          /  \ 
                         /    \
                        /      \
               13.2    /        \  12.2
                      B----------C
                      5.20     5.1


What happens is on router B, the arp cache for IP address 13.1 will somehow
get changed and show the ethernet address for 13.1 to be some device other
than the cisco. When this happened, I was able to track down a machine
whose IP address was configrued wrong. It was on a subnet attached to router
A, subnet 100, and configured as if it was on subnet 50. What surprised me was 
why that would hose the arp cache of router B. I could reproduce the 
problem by booting the machine and within a minute router B would update it's
arp cache showing IP address 13.1 being the machine I just booted. The machine
I booted did not have anything related to subnet 13 in it's configuration 
files. When this happens all traffic between routers A and B dies since router
B is directing it to the wrong interface. One thing I have done is create
a static arp entry but that really isn't the best way to handle this. Has
this been reported elsewhere and is there a fix for it?

Sincerely,
Jack suess
410-455-2582
jack@umbc3.umbc.edu



-- 
Jack Suess                           UMBC Academic Computing
Internet: Jack@umbc5.umbc.edu        Standard Disclaimer:
Bitnet: Jack@umbc                    The opinions expressed above are mine and
ATT: 301.455.2582                    not my employers.