Dual NIC Server and Load Balancing

[RICHARD MESSINGER]

I think a customer is causing some of their own problem and I am looking for some additional advice.

Situation: HP Server with dual nics connected to same switch that according to the network setup is load balancing on transmission based on MAC addresses. What I think is happening is that in doing this, when traffic is going through a router, the router is seeing two MAC's with the same IP and then has to thrash its ARP table before forwarding the packet out the WAN interface. this is causing delays and other problems. I am also wondering if the server is expecting the returning traffic to be coming in the same interface that it went out of and because it might not, is throwing away the packet and trying again.

Does anyone have suggestion on how best to provide the load balancing to the server through the 3750G switch?

Thanks.

[milan.kulik]

Hi,

is Etherchannel configured on the switch?

(http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3750/12225sea/3750scg/swethchl.htm)

I beleive if load balancing is configured correctly on the server side, it should reply with only one MAC address to the router ARP requests, so the router should have no problem.

See http://h18004.www1.hp.com/products/servers/networking/teaming.html

and

http://h200007.www2.hp.com/bc/docs/support/SupportManual/c00288924/c00288924.pdf

for some HP NIC teaming details.

Regards,

Milan