Source based routing

Sometimes you have more than one router in your network, and want different containers to use different routers. For that, you need to set up source-based routing on the host system. For example:

# /sbin/ip rule add from $IP table $TBL
# /sbin/ip route add default dev $ETH via $GW table $TBL
# /sbin/ip route add $NET dev $ETH table $TBL

where

• $IP is an IP address which should use non-default gateway. You can also use netmask here, e.g. 10.9.8.0/24 will mean that all containers with addresses like 10.9.8.x will be routed through the given gateway.
• $NET is an IP network which should be routed straight, that is, not through the gateway. E.g. 10.9.8.0/24.
• $ETH is the network interface to route to, e.g. eth0.
• $GW is a gateway for this IP address.
• $TBL is any free table number, I use numbers from 6 upwards. Note that tables 250-255 are usually reserved (see /etc/iproute2/rt_tables).

Note that every new non-standard gateway will require another table number.

For more details on routing rules, see man ip.

See also

• Forum thread #268
• Forum thread #492