Hello, Ive looked everywhere for a decent explanation for mac address substitution with the submac ena option on the alteon loadm balancers, but cant find one, could someone please tell me about how it is used and when you would need to use it. Thanks
Source MAC address substitution should be enabled under a coouple of circumstances;
1) When the topology is Direct Server Return. DSR is when the Alteon (or Application Switch) load balances the inbound packets for a session but the server response bypasses the Alteon and is returned directly to the client. See the Application Guide for details. Required to prevent MAC address flapping on a layer 2 switch.2) When the devices that are load balanced (certain web caches and FWs come to mind) respond back to the source MAC rather than ARPing and responding back to the default gateway MAC.
Originally the Alteon did not substitute the source MAC when it processed a frame at layer 4. It would just change the destination MAC and/or destination IP. When the above two scenarios came into play source MAC substitution had to be supported and so was added as a feature.
If not sure, globally enabling submac is never a bad idea.
Angler
cc> Hello,
Thanks thats good, does point/example (1) mean the alteon replaces the source mac with the routers one (where it came from) rather than its own, so the server reponse goes back to the router as opposed to back through the alteon? Im just trying to understand that thats all.
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