Changing The Maximum Number Of Paths For Bgp4 Load Sharing - Foundry Networks Switch and Router Installation And Configuration Manual

Foundry Switch and Router Installation and Configuration Guide
The router waits for the Hold Time to expire before ending the connection to a directly-attached BGP4 neighbor
that dies.
For directly attached neighbors, the router to immediately senses loss of a connection to the neighbor from a
change to the state of the port or interface that connects the router to its neighbor. For directly attached EBGP
neighbors, the router can use this information to immediately close the BGP4 session and TCP connection to
locally attached neighbors that die.
NOTE: The fast external fallover feature applies only to directly attached EBGP neighbors. The feature does not
apply to IBGP neighbors.
If you want to enable the router to immediately close the BGP4 session and TCP connection to locally attached
neighbors that die, use either of the following methods.
USING THE CLI
To enable fast external fallover, enter the following command:
BigIron(config-bgp-router)# fast-external-fallover
To disable fast external fallover again, enter the following command:
BigIron(config-bgp-router)# no fast-external-fallover
Syntax: [no] fast-external-fallover
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 BGP in the tree view to expand the list of BGP option links.
4. Click on the General link to display the BGP configuration panel, shown in Figure 19.2 on page 19-8.
5. Select Disable or Enable next to Fast External Fall Over.
6. Click the Apply button to apply the changes 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.

Changing the Maximum Number of Paths for BGP4 Load Sharing

Load sharing enables the Layer 3 Switch to balance traffic to a route across multiple equal-cost paths of the same
type (EBGP or IBGP) for the route.
To configure the Layer 3 Switch to perform BGP4 load sharing:
• Enable IP load sharing if it is disabled.
• Set the maximum number of paths. The default maximum number of BGP4 load sharing paths is 1, which
means no BGP4 load sharing takes place by default.
NOTE: The maximum number of BGP4 load sharing paths cannot be greater than the maximum number of
IP load sharing paths.
How Load Sharing Affects Route Selection
During evaluation of multiple paths to select the best path to a given destination for installment in the IP route
table, the last comparison the Layer 3 Switch performs is a comparison of the internal paths.
• When IP load sharing is disabled, the Layer 3 Switch prefers the path to the router with the lower router ID.
• When IP load sharing and BGP4 load sharing are enabled, the Layer 3 Switch balances the traffic across the
multiple paths instead of choosing just one path based on router ID.
19 - 28 December 2000