out-delay
Syntax
out-delay seconds;
Hierarchy Level
[edit logical-systems logical-system-name protocols bgp], [edit logical-systems logical-system-name protocols bgp group group-name], [edit logical-systems logical-system-name protocols bgp group group-name neighbor address], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp group group-name], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp group group-name neighbor address], [edit protocols bgp], [edit protocols bgp group group-name], [edit protocols bgp group group-name neighbor address], [edit routing-instances routing-instance-name protocols bgp], [edit routing-instances routing-instance-name protocols bgp group group-name], [edit routing-instances routing-instance-name protocols bgp group group-name neighbor address]
Description
Control how often BGP and the routing table exchange route information by specifying how long a route must be present in the Junos OS routing table before it is exported to BGP. Use this time delay to help bundle routing updates and to avoid sending updates too often.
Alternatively or in addition, external BGP (EBGP) sessions can also use the route-flap damping mechanism upon the reception of BGP messages coming from an external neighbor.
BGP stores the route information it receives from update messages
in the routing table, and the routing table exports active routes
from the routing table into BGP. BGP then advertises the exported
routes to its peers. The out-delay
statement enables a
form of rate limiting. The delay is added to each update for each
prefix individually. When a routing device changes its best path to
a destination prefix, the device does not inform its peer about the
change unless the route has been present in its routing table for
the specified out-delay
. If you use out-delay
to perform rate-limiting, you can expect a less bursty pattern of
updates. You will see a pattern in which updates arrive in a steady
flow, and two updates for the same prefix are always spaced by at
least the out-delay
timer value (for example, 30 seconds).
Thus, the out-delay
setting is useful for limiting oscillation
(sometimes called churn) in a network. Keep in
mind that, regardless of the out-delay
setting, BGP peers
exchange routes immediately after neighbor establishment. The out-delay
setting is only designed to delay the exchange of
routes between BGP and the local routing table.
Caution is warranted because an out-delay
can delay
convergence. If your network is configured in a way that avoids oscillation,
setting an out-delay
is not necessary.
When configured, the out-delay
value displays as Outbound Timer
when using show bgp group
or show bgp group neighbor
commands.
Default
By default, the exchange of route information between BGP and the routing table occurs immediately after the routes are received. This immediate exchange of route information might cause instabilities in the network reachability information. If you omit this statement, routes are exported to BGP immediately after they have been added to the routing table.
Options
seconds—Output delay time.
Range: 0 through 65,535 seconds
Default: 0 seconds
Required Privilege Level
routing—To view this statement in the configuration.
routing-control—To add this statement to the configuration.
Release Information
Statement introduced before Junos OS Release 7.4.