metric-out

Syntax

Hierarchy Level

Description

Specify the metric for all routes sent using the multiple exit discriminator (MED, or MULTI_EXIT_DISC) path attribute in update messages. This path attribute is used to discriminate among multiple exit points to a neighboring AS. If all other factors are equal, the exit point with the lowest metric is preferred.

You can specify a constant metric value by including the metric option. For configurations in which a BGP peer sends third-party next hops that require the local system to perform next-hop resolution—IBGP configurations, configurations within confederation peers, or EBGP configurations that include the multihop command—you can specify a variable metric by including the minimum-igp or igp option.

You can increase or decrease the variable metric calculated from the IGP metric (either from the igp or minimum-igp statement) by specifying a value for offset. The metric is increased by specifying a positive value for offset, and decreased by specifying a negative value for offset.

In Junos OS Release 9.0 and later, you can specify that a BGP group or peer not advertise updates for the MED path attributes used to calculate IGP costs for BGP next hops unless the MED is lower. You can also configure an interval to delay when MED updates are sent by including the med-igp-update-interval minutes statement at the [edit routing-options] hierarchy level.

Options

delay-med-update—Specify that a BGP group or peer configured with the metric-out igp statement not advertise MED updates unless the current MED value is lower than the previously advertised MED value, or another attribute associated with the route has changed, or the BGP peer is responding to a refresh route request.

igp—Set the metric to the most recent metric value calculated in the IGP to get to the BGP next hop. Routes learned from an EBGP peer usually have a next hop on a directly connected interface and thus the IGP value is equal to zero. This is the value advertised.

metric—Primary metric on all routes sent to peers.

• Range: 0 through 4,294,967,295 (2³² – 1)

• Default: No metric is sent.

minimum-igp—Set the metric to the minimum metric value calculated in the IGP to get to the BGP next hop. If a newly calculated metric is greater than the minimum metric value, the metric value remains unchanged. If a newly calculated metric is lower, the metric value is lowered to that value. When you change a neighbor’s export policy from any configuration to a configuration that sets the minimum IGP offset on an exported route, the advertised MED is not updated if the value would increase as a result, even if the previous configuration does not use a minimum IGP-based MED value. This behavior helps to prevent unnecessary route flapping when an IGP cost changes, by not forcing a route update if the metric value increases past the previous lowest known value.

offset—Increases or decreases the metric by this value.

• Range: –2³¹ through 2³¹ – 1

• Default: None

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.

Option delay-med-update introduced in Junos OS Release 9.0.