Cajun P550 Switch Overview

Cajun Routing Overview

The Cajun switch is an IP and IPX router with virtual interfaces. Virtual interfaces are mapped to physical ports or VLANs. Layer 3 IP traffic is routed between the virtual interfaces.

Ports become members of VLANs by assignment or by rules. Multiple VLANs can share a single trunk port. In contrast, multiple physical ports can be associated with a single VLAN. In all cases, traffic that arrives and leaves the same VLAN is bridged, not routed.

This section provides additional information that includes:

❒Compatibility with the Layer 2 Switch

❒Routing with Layer 2 and Layer 3 Modules

Compatibility with the Layer 2 Switch

The switch is completely backwards compatible with all of the Layer 2 media modules currently supported in the Cajun switch. Traffic from the Layer 2 media module is routed by sending that traffic to the routing engine on the Layer 3 supervisor module. The supervisor module routes all traffic from Layer 2 media modules in software as described in the section, “Routing with Layer 2 and Layer 3 Modules”.

Note: Layer 2 traffic that does not require routing is bridged independently of the Layer 3 traffic based on the MAC address or VLAN information.

Routing with Layer 2 and Layer 3 Modules

When the Cajun switch is configured with a mix of Layer 2 and Layer 3 modules, IP and IPX routing is performed by the Layer 3 media module or the Layer 3 supervisor module using special ASICs present on those modules. These ASICs contain an address cache (forwarding table) that can hold a maximum of 20,000 address cache entries. The entries consist of packet addressing information and next hop information that enable the switch to effectively route the packets to their destination.

The Layer 3 supervisor also maintains a master routing table. The master routing table contains up to 24,000 entries. This routing table enables the supervisor module to keep track of which entries are in each address cache. As a result, each time a change occurs in the master routing table, the Layer 3 supervisor module updates the appropriate address caches. For example, if a unicast route is removed from the master routing table, then all matching entries in forwarding tables are removed as well.

Cajun P550/P220 Switch Operation Guide

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