Static Routes – Next Hop IP address vs Exit Interface
In this video, we experiment with various ways of configuring static routes , what really happens under the hood and discuss the advantages and drawbacks associated with the same.
Setting the context – 00:00
IPv4 static routes configured with only an exit interface – 8:37
IPv4 static routes configured with only an next-hop IP address – 18:54
IPv4 static routes configured with both next-hop IP address and exit interface – 26:48
Bonus content – 31:03
FYI – 42:36, I had run the “show ip route” soon after the e0/1 was shut. Hence you see the 10.0.13.0/24 (connected route) has been removed from the routing table and the route from RIP hadn’t arrived on R1 yet. RIP sends periodic updates every 30 sec so you will see 10.0.13.0/24 ( RIP route via R2) if you run the show command again post 30 sec.
ip address
FYI – 42:36, I had run the "show ip route" soon after the e0/1 was shut. Hence you see the 10.0.13.0/24 (connected route) has been removed from the routing table and the route from RIP hadn't arrived on R1 yet. RIP sends periodic updates every 30 sec so you will see 10.0.13.0/24 ( RIP route via R2) if you run the show command again post 30 sec.
Nice content. Another point is, in some cases, we need to limit ARP responses for a given eth segment.
This result more strict routing policy and we need to define at least two RIB entry which they are more specific than our eth segment.
We can point to null interface for more specific routes but this isn't a good idea, so we will point to a trusted intermediate hop. Now the problem is, router no more have a next-hop reachability, since our ARP limiting specific routes points to any random eth neighbor.
The solution is to add exit interface in our more specific static entries. This will solve our routed networks reachability and any traffic destined to next hop itself but we have new problem, any another intermediate hop in this eth segment also need to static entry since we are still unable to point any directly connected entry.