static routes

[cormon]

When setting a static route on a cisco .As far as I know there are two ways of doing it

1) next hop address
ip route 192.168.1.0 192.168.1.2

2) The interface the route goes out on
ip route 192.168.1.0 S0

Heres my question what the differnce/advantage of using each.

Thanks in advance for your input

 

[anddaley]

There is non. It makes no difference.

 

[themut]

A static route pointing to a interface will add the route to the routing table only when that interface is up.

If the interface is a broadcast interface like Ethernet, the router considers all hosts within the range of the route to be directly connected through that interface, and as a result the router will send ARP requests to ALL of the destination addresses that route through that static route.
Now if the static route is also a default route, it could potentially cause high CPU and a very large ARP table.

If you configure the static route using a numerical next hop, then the router will not Proxy ARP for any of the destination IP addresses within the static route. Hope I made sense!

 

[anddaley]

Cool I always took that for granted. Thanks for clarifying that.

 

[squarefolkdancer]

Using an interface or ip address will affect the metric of the route, probably doesn't make any difference. Using an ip address will mean one more table look up, since THAT ip addres will have to be resolved to an interface. Probably doesn't make much difference unless you have large routing tables on a heavily loaded router. (and thanks themut, I didn't know about that problem with broadcast interfaces, so don't do it except on a serial interface)

 

[cormon]

thanks guys