On Sat, Aug 26, 2006 at 10:29:24AM -0400, suse@rio.vg wrote:
Why shouldn't you add ip addresses to loopback?
What would be the point? Nothing else on that network could access it. loopback is specifically for the local machine only, there's no reason to have multiple ip addresses for it, unless you're doing something very strange.
Just forgot to mention one other possible use of secondary IP address on the loopback interface. If you are using using Foundry Networks ServerIron load balancer with direct server return feature, you need that secondary IP on the loopback to use the server in a pool. A pool configured on the LB is assigned an IP address. The same IP address is configured as secondary on loopback on all servers in that pool. When a packet is sent to the pool IP address, LB receives it, then tweaks packet on layer 2 substituting MAC address with an address of one of the servers in the pool leaving destination IP address intact. The packet is delivered to the server in question, and IP stack on that server accepts the packet because the host has destination IP address on its looopback interface. The source IP address of the packet is kept intact, so the server sends a response directly to the client bypassing LB on the way back, hence the name "direct server return". -Kastus