Brocade Communications Systems ICX 7250 series, Руководство по настройке

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Enabling fast external fallover
BGP4 devices 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 becomes non-operational, the device waits until the Hold Time expires or the TCP connection fails
before concluding that the neighbor is not operational and closing its BGP4 session and TCP connection with the neighbor.
The device waits for the Hold Time to expire before ending the connection to a directly-attached BGP4 neighbor that becomes non-
operational.
For directly-attached neighbors, the device immediately senses loss of a connection to the neighbor from a change of state of the port or
interface that connects the device to the neighbor. For directly-attached EBGP neighbors, the device uses this information to
immediately close the BGP4 session and TCP connection to locally attached neighbors that become non-operational.
NOTE
The fast external failover feature applies only to directly attached EBGP neighbors. The feature does not apply to IBGP
neighbors.
To enable fast external fallover, enter the following command.
device(config-bgp-router)# fast-external-fallover
To disable fast external fallover again, enter the following command.
device(config-bgp-router)# no fast-external-fallover
Syntax: [no] fast-external-fallover
Changing the maximum number of paths for BGP4 Multipath load sharing
Multipath load sharing enables the device to balance traffic to a route across multiple equal-cost paths of the same route type (EBGP or
IBGP).
To configure the device to perform BGP4 Multipath load sharing:
• Enable IP load sharing if it is disabled.
• Set the maximum number of BGP4 load sharing paths. The default maximum number 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 Multipath 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 device performs
a final comparison of the internal paths. The following events occur when load sharing is enabled or disabled:
• When load sharing is disabled, the device prefers the path with the lower device ID if the compare-routerid command is
enabled.
• When load sharing and BGP4 Multipath load sharing are enabled, the device balances the traffic across multiple paths instead
of choosing just one path based on device ID.
Refer to How BGP4 selects a path for a route (BGP best path selection algorithm) on page 275 for a description of the BGP4 algorithm.
When you enable IP load sharing, the device can load-balance BGP4 or OSPF routes across up to four equal paths by default. You can
change the number load sharing paths to a value from 2 through 8.
Optional BGP4 configuration tasks
Brocade FastIron Layer 3 Routing Configuration Guide
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