Core routers
Core routers typically use a routing table to determine the best path for forwarding packets to their destination. The routing table contains information about the network topology, including network addresses, subnet masks, and the next hop for each destination. Here is an example of a routing table for a core router:
| Destination Network | Subnet Mask | Next Hop |
|---|---|---|
| 10.0.0.0 | 255.0.0.0 | 172.16.1.1 |
| 172.16.0.0 | 255.240.0.0 | 192.168.1.1 |
| 192.168.1.0 | 255.255.255.0 | 0.0.0.0 |
| Default | 0.0.0.0 | 172.16.1.2 |
In this example, the routing table has four entries. The first entry specifies that any traffic destined for the 10.0.0.0 network should be forwarded to the next hop address of 172.16.1.1. The second entry indicates that traffic for the 172.16.0.0 network should be forwarded to 192.168.1.1. The third entry is for the local network 192.168.1.0 and specifies that packets should be sent directly to their destination without any further routing. Finally, the fourth entry is the default route, which matches all traffic not covered by the previous entries and specifies that it should be forwarded to the next hop address of 172.16.1.2.
The routing table is stored in the router’s memory, and it is constantly updated as new routes are learned or old routes become invalid. The router uses this table to determine the best path for forwarding packets to their destination.
Providing Edge Routers
Edge routers also use a routing table to determine the best path for forwarding packets to their destination. The main difference between edge and core routers is that edge routers are typically deployed at the boundary of an organization’s network, where they connect to the Internet or other external networks.
Here is an example of a routing table for an edge router:
| Destination Network | Subnet Mask | Next Hop |
|---|---|---|
| 10.0.0.0 | 255.255.255.0 | 192.168.1.1 |
| 192.168.0.0 | 255.255.255.0 | 0.0.0.0 |
| Default | 0.0.0.0 | 203.0.113.1 |
In this example, the routing table has three entries. The first entry specifies that any traffic destined for the 10.0.0.0 network should be forwarded to the next hop address of 192.168.1.1. This might be a gateway to another subnet within the organization’s network. The second entry indicates that traffic for the 192.168.0.0 network should be sent directly to its destination without any further routing. Finally, the third entry is the default route, which matches all traffic not covered by the previous entries and specifies that it should be forwarded to the next hop address of 203.0.113.1. This might be a gateway provided by the Internet service provider (ISP) that connects the organization’s network to the Internet.
As with core routers, the routing table is stored in the router’s memory, and it is constantly updated as new routes are learned or old routes become invalid. The router uses this table to determine the best path for forwarding packets to their destination, ensuring that traffic is efficiently and securely routed between different networks.
