Static Route

1. Introduction to Static Routing

What is a Static Routing?

Static routing is a manual method of routing where network administrators explicitly define routes in a router’s routing table. Unlike dynamic routing protocols which automatically adjust to changes, static routing remains fixed unless updated manually.

Static routing is especially useful in environments where simplicity and control are prioritized, such as small networks or specific traffic management scenarios.

🔍 Example Scenario

Let’s consider a practical example to understand the need for static routing.

Configure Static Routing

In this network:

  • R1 is connected to Network 192.168.1.0/24 on interface G0/1.
  • R2 connects Network 192.168.1.0/24 on interface G0/0 and to Network 192.168.2.0/24 on interface G0/1.

The Problem:

Static Routing Where to send packet

R1 cannot communicate with the 192.168.2.0/24 network because there is no route in its routing table pointing to that destination.

R1# show ip route
C    192.168.1.0/24 is directly connected, GigabitEthernet0/1

Without an entry for 192.168.2.0/24, R1 does not know where to send packets.

Testing Connectivity:

R1# ping 192.168.2.1 
Sending 5, 100-byte ICMP Echos to 192.168.2.1, timeout is 2 seconds:  
.....  
Success rate is 0 percent (0/5)

The ping fails because R1 lacks a route to the 192.168.2.0/24 network.

2. Understanding Static Routes

🔍 Static Routes Syntax

Static routes are manually defined paths in a router’s routing table, used to indicate the specific IP address (next-hop IP) that the router should use to reach a given network. They are simple and reliable but require manual updates when the network changes.

Static Routing Command Syntax

✅ Components of a Static Route:

  • Destination Network: The target network
  • Subnet Mask: The mask of the destination network
  • Next-Hop IP: The IP address of the next router that indicates the path to the destination network
  • Administrative Distance (AD): An optional parameter to define the priority of the route. If omitted, a default AD of 1 is applied.

Administrative Distance (AD)

Static routes have an Administrative Distance (AD) of 1 by default, making them more trustworthy than most dynamic routing protocols (example RIP: 120, OSPF: 110). This ensures the static route is preferred over other routes unless explicitly overridden.

3. Configuring Static Routes

Now that we understand the problem and the theory, let’s solve it by configuring a static route.

Static Route Command Configuration

🔹 Configuration Command

R1(config)# ip route 192.168.2.0 255.255.255.0 192.168.1.2

Now we can see in the routing table our route to 192.168.2.0/24 using 192.168.1.2 as the next-hop:

R1# show ip route  
S    192.168.2.0/24 [1/0] via 192.168.1.2  
C    192.168.1.0/24 is directly connected, GigabitEthernet0/1

R1 now has a static route pointing to the 192.168.2.0/24 network via the next-hop 192.168.1.2 with AD set to 1 (by default).

🔹 Testing Connectivity After Configuration

R1# ping 192.168.2.1  
Sending 5, 100-byte ICMP Echos to 192.168.2.1, timeout is 2 seconds:  
!!!!!  
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/3 ms
Static Routing Testing Connectivity

The ping is now successful because the static route allows R1 to forward packets to the 192.168.2.0/24 network via R2.

4. Verifying and Troubleshooting Static Routes

Verifying Static Route

To confirm that static routes are correctly configured and active, use:

R1# show ip route
S    192.168.2.0/24 [1/0] via 192.168.1.2  
C    192.168.1.0/24 is directly connected, GigabitEthernet0/1

The static route is present and marked with an “S” indicating that it is manually configured.

Troubleshooting Static Route Issues

✅ Common Issues and Solutions:

  1. Missing Route Entries: Ensure the syntax and next-hop address are correct.
R1# show running-config | section ip route
ip route 192.168.2.0 255.255.255.0 192.168.1.2

2. Incorrect Next-Hop Address: Verify connectivity to the next-hop router using ping.

R1# ping 192.168.1.2  
!!!!!  
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/3 ms

3. Interface Down: Check interface status.

R1# show ip interface brief
Interface              IP-Address      OK? Method Status            Protocol  
GigabitEthernet0/1     192.168.1.1     YES manual up                up  
GigabitEthernet0/0     unassigned      YES unset  administratively down down

5. Conclusion

Static routing is a method where routes are manually defined on a router instead of being dynamically learned. This approach ensures precise traffic control and stability in a network. By configuring, verifying, and troubleshooting static routes, you can maintain efficient and reliable network connectivity! 🚀

Default Static Route