ip routing between two vlans using similar IP / subnet?

[lynx_nz]

I have a multi-tenated network with two seperate customers using the same IP and subnet range. Everything was rosy until these two different vLANs converged onto a 5406 with ip routing enabled... 

Situation ; 

vlan 10 (10.0.0.0/16)

vlan 20 (10.0.0.0/16) 

HP 5406 switch with ip routing enabled 

10.0.0.10 on vLAN 10 is able to ping 10.0.0.15 on vLAN 20?

As mentioned above, both these vlans were happy and there was no cross-over until they both hit a 5406 chassis which has ip routing enabled. the 5406 has no IPs defined on those vLANs and there are no routing rules between these two vlans or IP ranges. 

I would have assumed that both these vLANs would not be able to see each other. Or is this normal behavour? 

Thanks 

[manuel.bitzi · Accepted solution]

Should not!

Are you sure the traffic is interconnected between vlan 10 and 20 on this switch?

What does tracert say?

whats about the arp tables of the enddevices.

br

Manuel

[Fredrik Lönnman]

If the 5400zl indeed does not have an IP in any of the two VLANs it should work, then its just pure L2 through the 5400.

[lynx_nz]

Cheers, it was more of a sanity check for me. Cross over must be somewhere else. Hmmm.