CAT 6509 - One Mac to Mutiple IPs

howareb · ‎06-11-2003

I am in need of assistance with an issue. We have an installation of a Novell SFT III (2-server fault tolerence) solution that is on a subnet the uses the CAT 6509 as the layer 3 device. The SFT III communicates utilizing two seperate IPs per MAC address. Whenever the servers are booted the servers lose communication to the network. When you PING the 6509 repeatedly there is a lag time where the CAT 6509 just does not respond. After a while the ping will finally go through as normal. We have narrowed down the problem to be with the ARP address exchange, but suspect that the Cat 6509 is disallowing multiple IP addresses per mac address.

My question is, is there a feature or a setting that disallows one mac address to be associated with multiple ip addresses? We have other sites who use the Novell SFTIII soultion with Cisco equipment and we do not have a problem.

Was there newly implemented features released in an IOS that can explain why this is happening? Any help would be appreciated.

t.baranski · ‎06-11-2003

I have some HA devices using a single MAC address for multiple IP addresses connected to a 6509 without issue. I suspect your problem is something different. The same MAC address on multiple ports will certainly cause issues...

howareb · ‎06-12-2003

"The same MAC address on multiple ports will certainly cause issues..."

Can you elaborate about this comment more please. What kind of problems? The part of a redundant network infrastructure. Would that have anything to do with your comment.

t.baranski · ‎06-12-2003

Switches make layer-2 forwarding decisions based on MAC address. If a switch sees the same MAC address on multiple ports, it won't know which port to use to forward packets destined to that MAC address. Eventually you'll start seeing errors in the logs about the MAC address flapping between ports. The end result is that traffic destined to that MAC address will be severely disrupted.