[c-nsp] ARP entries from another subnet

[Vincent De Keyzer]

Hello,

 

I have the following weird situation:

* two LANs, A and B

* LAN A has IP 10.1.1.0/24

* LAN B has IP 10.2.2.0/24

* def. gateway for LAN A is router Ra = 10.1.1.1

* def. gateway for LAN B is router Rb = 10.2.2.1

* Ra and Rb are connected together via a network (cloud)

* host Ha = 10.1.1.10 is on LAN A

* host Hb = 10.2.2.10 is on LAN B

 

Now, something went wrong and LAN A and LAN B ended up connected together
(say: a UTP cable between the two switches).

 

Within the ARP table of Ha, there was an entry for 10.2.2.10 ! So to reach
Hb, it would go directly instead of using its default gateway (Ra).

 

How did this ARP entry arrive in there?

 

Vincent

 

PS: Ha is a Catalyst 2950.