Learning Static Route: Is this correct?

Question

In my network journey, I'm studying static routes now (I know that isn't used in large environments, but just studies).

I made this topology in GNS3, and I'm wondering if some points are correct.

PS: The .x are the IP of the interface.

The routing tables are:

**R1**
     172.16.0.0/24 is subnetted, 1 subnets
C       172.16.1.0 is directly connected, FastEthernet0/0
     10.0.0.0/30 is subnetted, 2 subnets
S       10.0.0.0 [1/0] via 10.0.1.2
C       10.0.1.0 is directly connected, FastEthernet1/0
C    192.168.1.0/24 is directly connected, FastEthernet0/1
S    192.168.2.0/24 [1/0] via 10.0.1.2
S    192.168.3.0/24 [1/0] via 10.0.0.2


**R2**
     10.0.0.0/30 is subnetted, 2 subnets
C       10.0.0.0 is directly connected, FastEthernet0/0
C       10.0.1.0 is directly connected, FastEthernet1/0
S    192.168.1.0/24 [1/0] via 10.0.1.1
C    192.168.2.0/24 is directly connected, FastEthernet0/1
S    192.168.3.0/24 [1/0] via 10.0.0.2


**R3**
     10.0.0.0/30 is subnetted, 2 subnets
C       10.0.0.0 is directly connected, FastEthernet0/0
S       10.0.1.0 [1/0] via 10.0.0.1
S    192.168.1.0/24 [1/0] via 10.0.1.1
S    192.168.2.0/24 [1/0] via 10.0.0.1
C    192.168.3.0/24 is directly connected, FastEthernet0/1

I'm wondering, for the R3 to reach the subnet 192.168.1.0, I do need to specify static routes for 10.0.1.0/30 AND 192.168.1.0?. Same goes for the R1 reach 192.168.3.0... Is this the way it works?

Answer 1

If your plan is to replicate the insanity of a dynamic routing protocol, then you're well on your way. :-)

No sane network engineer would ever add static routes to non-local endpoints. Your 192.168.3.0/24 on R1, for example, is routed to 10.0.0.2, which is not connected to it. In order to install that route in the table, a route to 10.0.0.2 (10.0.0.0/30) must exist. This just makes reading your config a pain. The router will make multiple passes over the RIB to build the active route table. (in this case, it'll sync in a fraction of a second.)

Textbook answer: The next-hop must be reachable for the route to be installed.

(Dynamic routing protocols may do this for other reasons. Humans tend to avoid it because it generates real headaches.)

Answer 2

This is one way to do it however not best practice, two things; 1/ If your router only has one connection outside of its LAN side in your case R3 only has fa0/0 which is connected to 10.0.0.0/30. You can just have a static default route 0.0.0.0 0.0.0.0 pointing to the next hop of 10.0.0.1 on R2. Treat R3 as a stub unless you add more interfaces.

2/ the static route you have configured: S 192.168.3.0/24 [1/0] via 10.0.0.2 should NEVER be used in real environment, pointing a static route to a local IP address rather than a directly connected next-hop will cause excessive ARP, each time a packet is sent out this interface in turn resulting in high CPU. Might not see this in GNS3 as it is all software processed in CPU anyway but on a real router (if Cisco) this will not be CEF switched.

Also as you said so many static routes is not a good idea, if you want to advertise your LAN networks just use a routing protocol...