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| 4.1 |  | Methods of Inter-VLAN Routing |
| 4.1.5 |  | Route switch processors |

The highest performing Inter-VLAN routing option utilizes an internal route switch processor. A route switch processor is essentially a router card that can be plugged into a modular switch. On some models, the route switch processor is not modular, but is an integral part of the switches hardware and architecture.

Route switch processors perform better than external routers for the following reasons:

- The CPU power of the router is well matched to the capacity of the switch.
- The router has direct access to the switches backplane. This offers more bandwidth than a physical interface.
- The router is highly integrated within the switch. This allows high-speed routing features such as Multilayer Switching (MLS) to be easily implemented.

In addition to the route switch processor’s high-speed routing performance, there can also be significant benefits in terms of ease of configuration and management. For most Catalyst switches, the route switch processor’s interfaces are actually specified as VLANs. For example, to configure an IP address for the routers interface in VLAN 55, the command would simply be:

> Switch(config)#interface vlan 55
> Switch(config-if)#ip address 10.0.1.1 255.255.255.0

This makes it difficult to mismatch router interfaces and VLAN IDs and produces layer 2 and layer 3 configuration files that are easier to interpret than when an external router is used.