Optimizing The Ip Forwarding Cache - Foundry Networks Switch and Router Installation And Configuration Manual

For optimal results, set the maximum number of paths to a value at least as high as the maximum number of
equal-cost paths your network typically contains. For example, if the Layer 3 Switch you are configuring for IP
load sharing has six next-hop routers, set the maximum paths value to six.
NOTE: If the setting for the maximum number of paths is lower than the actual number of equal-cost paths, the
software does not use all the paths for load sharing.
To change the number of paths, use either of the following methods.
USING THE CLI
To change the number of IP load sharing paths, enter a command such as the following:
BigIron(config)# ip load-sharing 8
Syntax: [no] ip load-sharing [<num>]
The <num> parameter specifies the number of paths and can be from 2 – 8.
USING THE WEB MANAGEMENT INTERFACE
1. Log on to the device using a valid user name and password for read-write access. The System configuration
panel is displayed.
2. Click on the plus sign next to Configure in the tree view to expand the list of configuration options.
3. Click on the plus sign next to IP in the tree view to expand the list of IP option links.
4. Click on the General link to display the IP configuration panel.
5. Edit the value in the # of Paths field. You can enter a number from 2 – 8.
6. Click the Apply button to save the change to the device's running-config file.
7. Select the Save link at the bottom of the dialog. Select Yes when prompted to save the configuration change
to the startup-config file on the device's flash memory.

Optimizing the IP Forwarding Cache

NOTE: This section applies only to chassis Layer 3 Switches.
The IP forwarding cache provides fast-path forwarding for IP traffic. The entries in the cache contain the following
information:
• Source IP address and TCP or UDP port
• Destination IP address and TCP or UDP port
The default cache settings are adequate for most situations. However, if the Layer 3 Switch forwards traffic to a
very large number of destination hosts or uses default routes to send traffic to a large number of destinations, you
may need to adjust the cache settings.
The software on chassis Layer 3 Switches allows you to adjust the following forwarding cache settings:
• Cache capacity for unicast forwarding entries – The forwarding cache contains a unique entry for each host
destination. You can set the cache to allow more unicast forwarding entries by enabling the high-
performance mode. This option enables the cache to contain more unique entries for unicast traffic.
• Cache format for default route entries – The forwarding cache contains a unique entry for each host
destination of a default route. You can increase the cache's capacity for default route entries by enabling the
default-route aggregation mode. This option increases the cache's capacity for default routes by
aggregating forwarding information for multiple destinations into single default-route entries.
These optimization options are disabled by default. To enable them, use the following procedures.
December 2000
Configuring IP
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