In the event that the internet connection is DOWN (box is fine just the
cable modem is down)
how do I set things up so I can take advantage of the second internet
connection?
there are more ideal [and complex] ways of setting up the connections
so you only use one firewall - maybe using the second as a failover -
but assuming you want to keep your infrastructure the same:
create a second routing table one the cable modem firewall, with a
default route of the other firewall.
(assuming the other firewall is 10.10.10.2 and the internal NIC is eth1)
# echo 2 >> /etc/iproute2/rt_tables
# ip rule add fwmark 3 table 2
# ip route add default via 10.10.10.2 dev eth1 table 2
write a simple bash script that pings the cable modem's gateway. on
failure, after a predetermined amount of time, add an "iptables" rule
such as the following to use the second routing table:
(assuming 10.10.10.0/24 is your internal LAN)
# iptables -t mangle -A PREROUTING -s 10.10.10.0/24 -j MARK --set-mark 3
You can extend your BASH script to remove the IPTABLES rule once it
re-establishes contact with your cable modem's gateway.
it's not an elegant solution, but it's a simple one.
-ken
Thanks for any tips.
Jerry
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