Task: A linux box has two aliaces configured on the interface:
em2: ip 10.10.0.10;
em2:0 - ip 10.10.11.1 and em2:1 - ip 10.10.22.2;

There are two routers that traffic can be forwarded to: 10.10.0.100 and 10.10.0.200. All traffic from 10.10.11.1 should be routed to 10.10.0.100 and traffic from 10.10.22.2 should be forwarded to 10.10.0.200.

IP routing

- rules - routing policy database

# ip rule list
 from all lookup local
 from all lookup main
 from all lookup default
  

- show routing tables:

# ip rule list

- generate a new table, called 'mytable1' and 'mytable2':
# echo 201 mytable1 >> /etc/iproute2/rt_tables
# echo 202 mytable2 >> /etc/iproute2/rt_tables


- add a new rule to the table (this like putting an interface into the VRF ):
# ip rule add from 10.10.11.1  table mytable1
# ip rule add from 10.10.22.2  table mytable2


- add a default route into our tables:
# ip route add default via 10.10.0.100 dev em2 table mytable1
# ip route add default via 10.10.0.200 dev em2 table mytable2
  

-in order to make this persistent and survive after reboot, this line can be added to the interface configs:

[server]# cat ifcfg-em2
DEVICE="em2"
BOOTPROTO="static"
IPADDR="10.10.0.10"
NETMASK="255.255.255.0"
ONBOOT="yes"
ip route add default via 10.10.0.100 dev em2 table mytable1
ip route add default via 10.10.0.200 dev em2 table mytable2

[server]# cat ifcfg-em2:0
DEVICE=em2:0
IPADDR=10.10.11.1
NETMASK=255.255.255.0
ONBOOT=yes
ip rule add from 10.10.11.1  table mytable1

[server]# cat ifcfg-em2:1
DEVICE=em2:0
IPADDR=10.10.22.2
NETMASK=255.255.255.0
ONBOOT=yes
ip rule add from 10.10.22.2  table mytable1
  

All Blogposts