My networking cisco assignment :)

My Cisco Assignment: Configuring Static and Default Routes 🛣️

I just completed the routing portion of my Enterprise Networking module, focusing on implementing both static and default routes across a multi-router topology. This assignment was crucial for understanding how routing decisions are made when dynamic routing protocols aren't in use.

The Network Topology and Goal

My setup involved three Cisco routers (R1, R2, and R3), each connected to different local subnets.

• R1 was connected to the ISP simulated cloud.
• R2 and R3 were internal routers.

The primary goal was to ensure full connectivity between all internal networks and also allow all internal traffic to reach the internet via R1, all by manually defining the paths.

Static Route Configuration (ip route)

The core of the assignment was configuring the specific paths between the internal networks. For any packet destined for a remote network that wasn't directly connected, I had to define a static route.

The command I used was: ip route [destination network] [subnet mask] [next-hop IP address]

For example, on R2, to reach a network connected to R3 (e.g., 192.168.3.0/24), I executed: R2(config)# ip route 192.168.3.0 255.255.255.0 [R3's interface IP address]

Key Takeaway: I had to define two static routes on each internal router (R2 and R3)—one for the other internal router's LAN and one pointing to R1 to get out to the "internet." Getting the mask right and the next-hop IP (the IP of the neighbor router's interface) was critical.

Default Route Configuration (The "Gateway of Last Resort")

The second, and arguably most important, part was configuring the default route on R1. This route acts as the "catch-all" path for any traffic that doesn't match a more specific route in the router's table. Since R1 was the edge router connected to the ISP, any unknown destination should be sent that way.

The command used was: ip route 0.0.0.0 0.0.0.0 [next-hop IP address of the ISP router]

• 0.0.0.0 0.0.0.0 effectively matches every network and every mask.
• Once this was configured, R1 had a "Gateway of Last Resort" set, meaning all packets destined for the internet were correctly forwarded.

I also configured a simpler default route on R2 and R3 that pointed all unknown traffic toward R1. This significantly reduced the number of specific static routes needed on the internal routers.

Troubleshooting and Verification 🛠️

My main challenge was remembering the difference between the next-hop IP method and the exit interface method for configuring the static route. I initially used the exit interface (ip route... Serial0/0/0) but this can sometimes cause issues with multi-access networks (like Ethernet), so I switched to consistently using the next-hop IP address for better performance and to avoid recursive lookups.

I verified everything using:

• show ip route static: To confirm only my manually added routes were present.
• show ip route: To check the full routing table and see the default route marked with an asterisk (*) as the candidate default route.
• ping and traceroute: To confirm end-to-end connectivity between internal PCs and successful access to the simulated "internet" network.

This assignment really cemented my understanding of how routing tables are built and prioritized in a hierarchical network. It was a great practical exercise!