On Sun, 2007-01-28 at 16:39 -0800, J.C. Roberts wrote: > On Sunday 28 January 2007 03:03, Soner Tari wrote: > > I'm running Postfix on OpenBSD and have multiple external links on > > the same box. I want outgoing smtp connections to be routed to > > ext_if2, but the rest to ext_if1. > > why?
Because the ext_if2 has a DSL connection which is faster and symmetrical, and more importantly has a C class IP, which is essential if you don't want to be considered as a spammer by many MTAs. Not to mention, one might need to load-balance based on ports. Other than the smtp port and Postfix, the ability to route based on destination port may be important for a firewall with multiple external links in general. Because you might like to route the traffic originating from the firewall itself to whichever link you wish, such as those by an http proxy.
