Juniper JUNOSE, Configuration Manual

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Setting Automatic Fallover
You can use the bgp fast-external-fallover command to specify that in the event of
the failure of a link to any adjacent external peer, the BGP session is immediately
and automatically brought down rather than waiting for the TCP connection to fail
or for the hold timer to expire.
bgp fast-external-fallover
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Use to immediately bring down a BGP session if the link to an adjacent external
peer fails.
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If you do not issue this command, the BGP session is not brought down in the
event of a link failure until the TCP connection fails or the hold timer expires.
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This command takes effect immediately.
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Use the no version to stop automatically bringing down the session in the event
of link failure.
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See bgp fast-external-fallover.
Setting Timers
BGP uses a keepalive timer to control the interval at which keepalive messages are
sent. A hold-time timer controls how long BGP waits for a keepalive message before
declaring a peer not available.
BGP negotiates the hold time with each neighbor when establishing the BGP
connection. The peers use the lower of the two configured hold times. BGP sets the
keepalive timer based on this negotiated hold time and the configured keepalive
time.
neighbor timers
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Use to set the keepalive and hold-time timers for the specified neighbor or peer
group.
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Overrides timer values set with the timers bgp command.
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If you specify a BGP peer group by using the peerGroupName argument, all the
members of the peer group inherit the characteristic configured with this
command unless it is overridden for a specific peer.
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If you set the keepalive timer to 0, BGP does not send any keepalive messages.
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If you do not expect the peer to send any keepalives, set the hold-time timer
to 0.
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This command takes effect immediately and automatically bounces the session
to force BGP to send a new open message to renegotiate the new timer values.
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Example
host1(config-router)# neighbor 192.168.21.5 timers 90 240
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Configuring BGP Peer Groups
JUNOSe 11.0.x BGP and MPLS Configuration Guide