Installation and Getting Started Guide

To display the IP route table, see the following:

•“Displaying the IP Route Table” on page 6-90– routing switch only To configure a static IP route, see the following:

•“Configuring Static Routes” on page 6-36– routing switch only

To clear a route from the IP route table, see the following:

•“Clearing IP Routes” on page 6-93– routing switch only

To increase the size of the IP route table for learned and static routes, see the “Configuring Basic Features” chapter of the Installation and Getting Started Guide:

•For learned routes, modify the ip-route parameter.

•For static routes, modify the ip-static-route parameter.

IP Forwarding Cache

The IP forwarding cache provides a fast-path mechanism for forwarding IP packets. The cache contains entries for IP destinations. When an HP ProCurve routing switch has completed processing and addressing for a packet and is ready to forward the packet, the device checks the IP forwarding cache for an entry to the packet’s destination.

•If the cache contains an entry with the destination IP address, the device uses the information in the entry to forward the packet out the ports listed in the entry. The destination IP address is the address of the packet’s final destination. The port numbers are the ports through which the destination can be reached.

•If the cache does not contain an entry and the traffic does not qualify for an entry in the session table instead, the software can create an entry in the forwarding cache.

Each entry in the IP forwarding cache has an age timer. If the entry remains unused for ten minutes, the software removes the entry. The age timer is not configurable.

NOTE: The HP 6208M-SX does not have an IP forwarding cache.

Here is an example of an entry in the IP forwarding cache:

 

IP Address

Next Hop

MAC

Type

Port

Vlan Pri

1

192.168.1.11

DIRECT

0000.0000.0000

PU

n/a

0

Each IP forwarding cache entry contains the IP address of the destination, and the IP address and MAC address of the next-hop router interface to the destination. If the destination is actually an interface configured on the routing switch itself, as shown here, then next-hop information indicates this. The port through which the destination is reached is also listed, as well as the VLAN and Layer 4 QoS priority associated with the destination if applicable.

To display the IP forwarding cache, see “Displaying the Forwarding Cache” on page 6-88.

NOTE: You cannot add static entries to the IP forwarding cache, although chassis routing switches do have options to optimize the cache and increase the number of entries the cache can contain. See “Optimizing the IP Forwarding Cache” on page 6-60and the “Configuring Basic Features” chapter of the Installation and Getting Started Guide.

To increase the size of the IP forwarding cache, see the “Configuring Basic Features” chapter of the Installation and Getting Started Guide. The ip-cache parameter controls the size of the IP forwarding cache.

Layer 4 Session Table

The Layer 4 session provides a fast path for forwarding packets. A session is an entry that contains complete Layer 3 and Layer 4 information for a flow of traffic. Layer 3 information includes the source and destination IP addresses. Layer 4 information includes the source and destination TCP and UDP ports. For comparison, the IP forwarding cache contains the Layer 3 destination address but does not contain the other source and destination address information of a Layer 4 session table entry.

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