Sunday, 31 March 2013

Configuring Persistent static route in Linux

Static routing

Static routing is a form of routing that occurs when a router uses a manually-configured routing entry, rather than information from a dynamic routing protocol to forward traffic. In many cases, static routes are usually manually configured by a network administrator by adding in entries into a routing table, though this may not always be the case.

Unlike dynamic routing, static routes are fixed and do not change if the network is changed or reconfigured. Static routing and dynamic routing are not mutually exclusive. Both dynamic routing and static routing are usually used on a router to maximize routing efficiency and to provide backups in the event that dynamic routing information fails to be exchanged. Static routing can also be used in stub networks, or to provide a gateway of last resort.

Static routes will be added usually through "route add" command. The drawback of 'route' command is that, when Linux reboots it will forget static routes. But to make it persistent across reboots, you have to add it to /etc/sysconfig/network-scripts/route-<eth> .

To add static route using "route add": 

# route add -net 192.168.100.0 netmask 255.255.255.0 gw 192.168.10.1 dev eth0 

Adding Persistent static route:

You need to edit /etc/sysconfig/network-scripts/route-eth0 file to define static routes for eth0 interface. 
GATEWAY0=192.168.10.1
NETMASK0=255.255.255.0
ADDRESS0=192.168.100.0

GATEWAY1=10.64.34.1
NETMASK1= 255.255.255.240
ADDRESS1=10.64.34.10 
Save and close the file. Restart networking: 
# service network restart 
Verify new routing table: 
# route –n 
# netstat –nr

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