Date: Sat, 25 Jun 2005 07:38:20 -0400 From: Doug Lee <dgl@dlee.org> To: freebsd-questions@freebsd.org Subject: Is this a safe way to multi-home a mail server? Message-ID: <20050625113819.GI950@kirk.dlee.org>
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I have a machine on two DSL networks: a /29 and a /28 provided by different ISPS (why is a long story). The machine acts as a mail server (sendmail) as well as a NAT server for an internal network. Both DSL nets arrive at one interface card, and the LAN is on the other card. I have added one of the DSL nets as the main net for the external interface and the other DSL net as an alias via ifconfig. Two questions: 1. Can I have both host IPs (one from each DSL net) as A records in DNS for the mail server's name--e.g., mail.my.domain IN A 1.2.3.4 mail.my.domain IN A 5.6.7.8 and expect mail to arrive at the machine regardless of which network is working at any given time? (Part of the "long story" is that we're having serious trouble with one or the other network at various times and are trying, temporarily at least, to stay afloat by using whichever is better at the moment.) Both host IPs have correct (identical) reverse DNS. 2. Is there a way, via routed or other means, to cause the machine to figure out automatically which net to use for "default" traffic? It would be wonderful if natd could keep up with this too, but there I suspect I'm asking for the moon... Thanks much for any responses. Please Cc me. -- Doug Lee dgl@dlee.org http://www.dlee.org BART Group doug@bartsite.com http://www.bartsite.com "I before E, except after C, or when sounded like A, as in neighbor and weigh, except for when weird foreign concierges seize neither leisure nor science from the height of society."
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