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5 graceful restart, Graceful restart – Siemens S223 User Manual

Page 323

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User Manual UMN:CLI
SURPASS hiD 6615 S223/S323 R1.5

A50010-Y3-C150-2-7619 323

To compare MED values on the exchange of path information between Confederation
Peers, use the following command.

Command Mode

Description

bgp bestpath med confed

[miss-

ing-as-worst

]

bgp bestpath med missing-as-

worst

[confed]

Router

Configures the router to consider the MED in choosing
a path from among the paths on the exchange of in-
formation between confederation peers.

To ignore MED values of paths on the exchange of information between confederation
peers, use the following command.

Command Mode

Description

no bgp bestpath med confed

[missing-as-worst]

no bgp bestpath med missing-

as-worst

[confed]

Router

Ignores MEDs of paths on the exchange of their infor-
mation between confederation peers.

If there are several equal paths, one of them has no MED value. Because this path is
considered as “zero” without MED value, it will be chosen the best path. But the path
would be the worst one if it has no MED value after missing-as-worst is set.

After missing-as-worst parameter is configured in the system, the path will be recog-
nized as the worst path without MED value.

10.1.2.5 Graceful

Restart

Graceful restart allows a router undergoing a restart to inform its adjacent neighbors and
peers of its condition. The restarting router requests a grace period from the neighbor or
peer, which can then cooperate with the restarting router. With a graceful restart, the re-
starting router can still forward traffic during the restart period, and convergence in the
network is not disrupted. The restart is not visible to the rest of the network, and the re-
starting router is not removed from the network topology.

The main benefits of graceful restart are uninterrupted packet forwarding and temporary
suppression of all routing protocol updates. Graceful restart thus allows a router to ex-
change path information with the neighboring router.

To configure graceful restart specifically for BGP, use the following command.

Command Mode

Description

bgp graceful-restart

Sets to use graceful restart in BGP protocol.

no bgp graceful-restart

Router

Disables the restart time value setting.

Therefore, 2 options of the time can be used to speed up routing convergence by its peer
in case that BGP doesn’t come back after a restart.

i

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