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I have two routers that are connected with a DCE cable on Interface Se2/0(both sides).

The two routers have one computer each with ip addresses as:

  • 1.1.1.1 with mask 255.255.255.0 -> router1 IP on interface Fa0/0
  • 2.2.2.2 with mask 255.255.255.0 -> router2 IP on interface Fa0/0

The ip addresses on interfaces Se2/0 are set as:

  • 11.11.11.11 with mask 255.255.255.0 -> router1 IP on interface Se2/0
  • 22.22.22.22 with mask 255.255.255.0 -> router1 IP on interface Se2/0

Adding the routes should go as:

  • ip route 2.2.2.0 255.255.255.0 22.22.22.22 -> for router1.
  • ip route 1.1.1.0 255.255.255.0 11.11.11.11 -> for router2.

However, these routes aren't established. If I use the show ip route command, it shows(router1 inpute for example),without the route shown:

1.0.0.0/24 is subnetted, 1 subnets
  C 1.1.1.0 is directly connected, FastEthernet0/0
11.0.0.0/24 is subnetted, 1 subnets
  C 11.11.11.0 is directly connected, Serial2/0

What am I doing wrong? My initial thought is I'm messing up the masks? Because I tried another address(for example 10.0.0.1 with mask 255.255.255.252) and it worked.

Networks and configuration(for only one router, symetric with the other router):

Networkss Configuration

Configuration continued

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  • Instead of telling what you've done, please show the actual onfigurations. – Teun Vink Dec 25 '16 at 17:22
  • Never use images for text. Copy the configurations (full configurations), paste them into your question, and use the Preformatted text feature ({}) on it. – Ron Maupin Dec 25 '16 at 18:05
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 15 '17 at 16:57
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Your static route, ip route 2.2.2.0 255.255.255.0 22.22.22.22 on Router 1 doesn't work because Router 1 doesn't know how to get to 22.22.22.22, so it cannot send traffic destined for the 2.2.2.0/24 anywhere, and it drops the traffic. The same thing applies to Router 2.

Routers learn how to get to other networks in three ways:

  1. Directly connected networks.
  2. Statically configured routes, but the router needs to know how to get to the next hop.
  3. By sharing routes through a common routing protocol.

If your two routers share a common network between them, each router knows to send the traffic on that interface because the network is directly connected to both routers.

You could also use something like, ip route 2.2.2.0 255.255.255.0 Serial2/0, but that is not a good idea for other reasons.

1

Your two serial interfaces have to be on the same subnet like on a side 11.11.11.11 and on the other side 11.11.11.12.

The directly connected interfaces always have to be on the same subnet.

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