Foundry Configuration Guide for the FESX, FSX, and FWSX
21 - 22
© Foundry Networks, Inc.
December 2005
To change the BGP4 update timer value, enter a command such as the following at the BGP configuration level of
the CLI:
FESX424 Router(config-bgp-router)# update-time 15
This command changes the update timer to 15 seconds.
Syntax:
[no] update-time <secs>
The <secs> parameter specifies the number of seconds and can be from 1 – 30. The default is 5.
Enabling Fast External Fallover
BGP4 routers rely on KEEPALIVE and UPDATE messages from neighbors to signify that the neighbors are alive.
For BGP4 neighbors that are two or more hops away, such messages are the only indication that the BGP4
protocol has concerning the alive state of the neighbors. As a result, if a neighbor dies, the router will wait until the
Hold Time expires before concluding that the neighbor is dead and closing its BGP4 session and TCP connection
with the neighbor.
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 immediately senses loss of a connection to the neighbor from a change
of 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.
To enable fast external fallover, enter the following command:
FESX424 Router(config-bgp-router)# fast-external-fallover
To disable fast external fallover again, enter the following command:
FESX424 Router(config-bgp-router)# no fast-external-fallover
Syntax:
[no] fast-external-fallover
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.
Содержание FastIron Edge Switch X424
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