Static routing question

Jayem

I've been doing packet tracer assignments and I came across packet tracert lab 1.3.5. Where you need to assign static routes from network 192.168.1.0 to 192.168.4.0 and another static route from 192.168.4.0 to 192.168.1.0. The whole point is to have PC 1 on the 192.168.1.0 network to ping PC2 on the 192.168.4.0 network. When I tried to assign both static routes when a next hop address I only got 50% completion, this reason being is I had to configure one of the static routes with an exit interface instead of a next-hop address. After doing said, I would receive 100% completion of the lab. I was able to ping to either PC no problem. My question is what is the deciding factor when configuring a static route, next-hop or exit interface? Are there any drawbacks from using either or is it at the direction of whom is configuring?

I hope that is enough information to go off of. This is more curiosity than anything else, thanks

azaghul

Sometimes it comes down to the technology you are using and if you know the next hop address.

EdTheLad

Choosing next-hop vs exit interface is dependent on the layer 2 protocol being used.
For example ethernet is a multiaccess technology, to be able to send a frame out on an ethernet segment you need to know the destination mac address of the remote device, to do this you need arp. If you point a static route to an exit interface, the router needs to send an arp request( with the dest ip address in your route statement "ip route x.x.x.x) out the ethernet interface.Will the remote device process the arp request as its local interface ip address is different from that in the arp?? only if proxy-arp is configured on the remote side.So to be able to use a static route pointing to the exit interface, proxy arp must be configured.
Downside to this is you could have alot of arp traffic on this interface as every packet with a unique dest address that hits this static route will need arp ran.Larger arp cache.

No issue using exit interface with point-to-point interface i.e. serial.

My advices is use the next-hop ip address everywhere unless you have some restriction that's forcing you to use the exit interface.
You can also use a combination of both.

You will read in many books that a route to exit interface has an admin distance of 0 while a route to next-hop has an AD of 1, this is not true however, both have an AD of 1.
The only other difference between these 2 routes is that the route to exit interface is classified as a "connected route" while the route to next-hop is classified as a "static route. You have to be careful with this when you want to redistribute static or connected routes into a routing protocol.