Insert routes into table manually with static routing

This is just an experiment i was trying to do, may be doesn’t make any sense in real life networks.
Experiment:
Define static routes on R1- R2- R3 such end to end interfaces from R1-R2 and R2-R3 all interfaces have different subnet .

Configuring IP addresses on interfaces

For Router1
R1>enable
R1#conf igure terminal
R1(config)#interface Serial0/0
R1(config)# ip address 71.4.32.1 255.255.255.252
For Router2
R2>enable
R2#conf igure terminal
R2(config)#interface Serial0/0
R2(config)# ip address 71.4.32.5 255.255.255.252
R2(config)#interface Serial0/1
R2(config)# ip address 71.4.32.9 255.255.255.252

For Router3
R3>enable
R3#conf igure terminal
R3(config)#interface Serial0/0
R3(config)# ip address 71.4.32.13 255.255.255.252
Checking ip address on Router interfaces

Configuring Static routes on Router R1

1. In the first line, we are Assigning Static Route to R2 – S0/0
Where
ip route – used for assigning static ip routing .
71.4.32.4 – defines the destination network address .
255.255.255.252- defines subnet mask of destination (71.4.32.4 ) network address .
S0/0- defines the interface of router R1 from which packet should came out to reach destination.
Note: Instead of using interface of router, we can also use next hop ip address
I.e. In this, 71.4.32.5 will be defined instead of s0/0.
2. Second line defines static route from R1 to R2-s0/1
3. Third one used to define static route for R3-s0/0.
In the same way, we will define static routes for R2 and R3.

For R2:

For R3:

Checking the ip routes on routers .
For R1:


For R2:

For R3:

Should it work or not …..confusion ?
Why it should not work :
Since end to end interfaces of routers having different subnet and thus to make communication between them we need to use a Router to communicate them (L3 device).
Why it should work:
As we have defined static routes, router will just check :
• In which network it has to send packet.
• From which interface it packet will should be send.

So, if we take example from router R1 to R3-s0/0

  • Router R1 will send packet from it’s S0/0 that will when reach interface of it’s end to end connected router (R2) interface s0/0.
  • Now router R2 will check in it’s routing table if it has path for 71.4.32.13/30.

Yes, there static route exist in R2 routing table as it’s network address is 71.4.32.12

Now, On R2 we have defined path to 71.4.32.12(network address of 71.4.32.13) thorough interface S0/0.

Thus, packet reach the destination .

Similarly, process will work for other routes from all routers.

Difference in routing table when end to end devices IP addresses are defines in same Subnet or in different Subnet

  • For end to end interfaces with different subnet

For End to end interfaces with same subnet

S – Static route
C – Connected route

Now, that’s obvious that makes conclusion :

  • if subnet will be changed on end to end interfaces and we need to define static routes to send packets to/through next hop interface and routing table add that route as Static Route. Display them as S
  • If subnet remain same on end to end interfaces, no need to define static routes for them as they are directly connected . display them as C