[CentOS] Networking Issue

Tue Jun 9 01:20:15 UTC 2009
Joseph L. Casale <JCasale at activenetwerx.com>

Need some opinions on making a multihomed box more resilient to
failure. This server runs asterisk and performs nat and firewalling
for an office. Its wan nic is plugged directly into a cable modem
and I am stuck with it being configured as a dhcp client. The lan
nic services a small office, and has a static IP but of course, no
default gateway.

When an internet outage occurs, asterisks sip stack tanks and the pbx
dives. So I have setup fqdn's/ip's in the hosts file for all sip peers
it will attempt to resolve, and setup a local dns with all rfc1912 zones
so every query asterisk can possibly make will be answered locally.

Now it seems there is still one last hurdle, when the connection is yanked
to simulate a complete outage, asterisk still goes down. I can only assume
this happens now as a result of no default gateway?

Would setting up a silly route for 0.0.0.0/0 to say 127.0.0.1 for the internal
nic in /etc/sysconfig/network-scripts/route-eth1 with a metric higher than
what the ISP's dhcp servers default gw would be possibly cure this? My hope
is that when the wan nic goes down, a route is still available.

I can't think of any other network shortcoming that is left when that external
nic goes down, I am hoping this is finally it, so asterisk will stop core
dumping and yelling "Serious Network Trouble".

Thanks!
jlc