Noel Alvarez

In this example there is a router with a hostname of “router-2″ that has a serial interface configured with the Internet Protocol (IP) address of 172.16.4.2. Without an entry in the host table of the router or a Domain Name System (DNS) server I cannot use the hostname of the router in order to ping or telnet to the device.

router-1#ping router-2
Translating “router-2″
% Unrecognized host or address, or protocol not running.

router-1#telnet router-2
Translating “router-2″
% Unknown command or computer name, or unable to find computer address

To create a host table entry that provides name resolution for “router-2″ that points to IP address 172.16.4.2 I use the following commands.

router-1#config t
Enter configuration commands, one per line. End with CNTL/Z.
router-1(config)#ip host router-2 23 172.16.4.2
router-1(config)#^Z

The above command “ip host” is provided the name of the device (router-2), default telnet port (23) and the IP address of the router. I may then check this entry using the “show hosts” command.

router-1#show hosts
Default domain is not set
Name/address lookup uses static mappings

Host Flags Age Type Address(es)
router-2 (perm, OK) 0 IP 172.16.4.2

Additionally, I may test the entry by pinging and telnetting to the router using the hostname provided in the host table.

router-1#ping router-2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to 172.16.4.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms
router-1#telnet router-2
Trying router-2 (172.16.4.2)… Open
User Access Verification

Password:

Enjoy!

You may use the following method to add a static route to the routing table of a Cisco router.

Before configuring the static route(s) you may run the following commands in order to get a better idea of the network(s) configured on the existing router.

router-1#show ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, * – candidate default
U – per-user static route

Gateway of last resort is not set

172.16.0.0/24 is subnetted, 2 subnets
C 172.16.4.0 is directly connected, Serial0
C 172.16.3.0 is directly connected, Ethernet0

router-1#show cdp entry * protocol
Protocol information for router-2 :
IP address: 172.16.4.2

The “show ip route” command provides us with the directly connected routes/networks. Additionally, the “show cdp entry * protocol” command provides the Internet Protocol (IP) address of a directly connected router (172.16.4.2) which we will use to complete the static routing entry. Before creating the static routing entry use the “ping” command to be certain you can reach the next hop router.

router-1#ping 172.16.4.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to 172.16.4.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms

Now, we may begin creating the static routing entry.

router-1#config t
Enter configuration commands, one per line. End with CNTL/Z.
router-1(config)#ip route 172.16.5.0 255.255.255.0 172.16.4.2 permanent
router-1(config)#^Z

The “ip route” tells the router it is a static entry, 172.16.5.0 is the network to be reached, 255.255.255.0 is the subnet mask of the 172.16.5.0 network, the IP address of 172.16.4.2 is the address of the router that will accept and forward the packet (router-2) and the “permanent” tells the router to keep the entry in the routing table even if the network can’t be reached (such as the interface of the 172.16.5.0/24 network being down).

Next, you may use the “show ip route” command to verify the route in the routing table.

router-1#show ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, * – candidate default
U – per-user static route

Gateway of last resort is not set

172.16.0.0/24 is subnetted, 3 subnets
C 172.16.4.0 is directly connected, Serial0
S 172.16.5.0 [1/0] via 172.16.4.2
C 172.16.3.0 is directly connected, Ethernet0

As you can see from the output above the 172.16.5.0/24 is in the routing table. Now, you may ping the gateway of the network, in this example it is 172.16.5.1, to verify network connectivity.

router-1#ping 172.16.5.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to 172.16.5.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms

Enjoy!

The following example is utilizing two Cisco 2500 series routers with two serial interfaces and two ethernet interfaces. I created a lab Wide Area Network (WAN) in order to configure static routes on Cisco routers. My goal was to create a static route from the ethernet interface (172.16.3.1) on router-1 to reach the ethernet interface (172.16.5.1) on router-2. After creating the static route on the router-1 ethernet interface (172.16.3.0/24) to reach the 172.16.5.0/24 network on the ethernet interface of router-2 I was still unable to ping the 172.16.5.0/24 network from the 172.16.3.0/24 network. I then began troubleshooting.

My first thought was that the network cable could be the cause due to the fact that I had not used it prior. After switching the network cable in question with a known good cable and receiving the same results I was able to rule out the network cable as the cause of the issue.

My next suspicion was that the ethernet interface on router-2 was possibly dead. I knew this was not the case after viewing the results of the “show ip interface brief” command and seeing the interface was up/up.

router-2#show ip interface brief
Interface IP-Address OK? Method Status Protocol
Ethernet0 172.16.5.1 YES NVRAM up up
Serial0 172.16.4.2 YES NVRAM up up
Serial1 unassigned YES unset administratively down down

My next step in troubleshooting was to view the static route entry I previously created from the 172.16.3.0/24 network to the 172.16.5.0/24 network using the “show running-config” command. I did not use the “show ip route” command because the static route entry would not have shown itself in the routing table due to the fact that the two networks were not communicating (only networks that communicate show up in the routing table). Upon inspecting the static routing entry I realized I made a mistake in the command syntax and created a new static route entry from the 172.16.3.0/24 network on router-1 to the 172.16.5.0/24 network on router-2. Please keep in mind that the two prior networks are configured on the ethernet interfaces of the router and are separated by the WAN (172.16.4.0/24) on the serial0 interfaces of the routers. The new static entry looks like this.

router-1#config t
Enter configuration commands, one per line. End with CNTL/Z.
router-1(config)#ip route 172.16.5.0 255.255.255.0 172.16.4.2 permanent
router-1(config)#^Z

I then verified the route in the routing table.

router-1#show ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, * – candidate default
U – per-user static route

Gateway of last resort is not set

172.16.0.0/24 is subnetted, 3 subnets
C 172.16.4.0 is directly connected, Serial0
S 172.16.5.0 [1/0] via 172.16.4.2
C 172.16.3.0 is directly connected, Ethernet0

I tested the entry using the “ping” command from router-1.

router-1#ping 172.16.5.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to 172.16.5.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms
router-1#ping 172.16.5.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to 172.16.5.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms

The Internet Protocol (IP) address of 172.16.5.1 is the default gateway of the 172.16.5.0/24 network and the IP address of 172.16.5.2 is the host on the network. As you can see from the output above this static route entry was entered correctly and is functioning properly.

Enjoy!