Tip

This is the documentation for the 20.02 version. Looking for the documentation of the latest version? Have a look here.

BGP Router Configuration¶

This statement enters BGP Server mode and sets the autonomous system number for this router to 65002, and enters config-bgp mode.

tnsr(config)# route dynamic bgp
tnsr(config-frr-bgp)# server 65002
tnsr(config-bgp)#

BGP mode defines the main behaviors of the BGP daemon, as well as the neighbors and behavior of BGP for different address families, among other possibilities.

From within config-bgp mode, the following commands are available:

address-family (ipv4|ipv6) (unicast|multicast):

Enter BGP Address Family Configuration mode.

always-compare-med:

Instructs the BGP daemon to always consult MED values in routes, no matter which AS the routes were received through.

bestpath as-path (confed|ignore|multipath-relax|as-set|no-as-set):

Controls how the BGP daemon determines the best path to a destination. May be one of:

confed:: Considers the length of confederation path sets and sequences.
ignore:: Ignores AS path lengths when computing the route to a destination.
multipath-relax:: Consider paths of equal length when choosing between multiple paths to a destination, rather than looking for an exact match. This allows load sharing across different AS paths, so long as they are of equal length.
as-set:: For use with multipath-relax, it adds AS set information for aggregate routes.
no-as-set:: For use with multipath-relax, it prevents AS set generation.

bestpath compare-routerid:

Uses the router ID of peers (or originator ID, if present) to break ties when computing paths to a destination based on other information. A lower router ID will win in a tie.

bestpath med confed:

Compare confederation path MEDs

bestpath med missing-as-worst:

If a route is missing MED information, it will be considered least preferred.

client-to-client reflection:

Enables reflection of routes from one client to another client.

cluster-id (<ipv4>|<value>):

Configures the BGP daemon to participate in route reflection with the given cluster ID. The ID may be given in IP address (dotted quad) notation or as an unsigned 32-bit integer (1-4294967295).

coalesce-time <value>:

Configures the Subgroup coalesce timer, in milliseconds (1-4294967295).

confederation identifier <ASN>:

Configures an AS number for the entire group of IBGP routers participating in confederation.

confederation peer <ASN>:

Configures the sub-AS number for the subset of peers inside a group of IBGP routers participating in confederation.

dampening [penalty <val> [reuse <val> [suppress <val> [maximum <max>]]]]:

This command enables BGP route flap dampening (RFC 2439) to prevent unstable routers from adversely affecting routing behavior.

penalty <penalty-val>:: The time duration during which the stability value will be reduced by half if the route is unreachable.
reuse <reuse-val>:: Stability threshold that must be crossed for a route to be reused.
suppress <suppress-val>:: Stability threshold that, when crossed, a route will be suppressed.
maximum <suppress-max>:: Maximum time to suppress a route considered stable.

deterministic-med:

Determine route selection locally, even when MED values are present. Picks the best MED path from neighbor advertisements.

disable-ebgp-connected-route-check:

Disable checking if nexthop is an eBGP session.

enforce-first-as:

When set, enforces the first AS for eBGP routes.

listen limit <value>:

Maximum number of dynamic neighbors from 1-5000.

listen range (<ip4-prefix>|<ip6-prefix>) peer-group <peer-group-name>:

Listen range for dynamic neighbors.

max-med administrative [<med>]:

Sends the defined MED value, or 4294967294 when unset, at all times.

max-med on-startup period <seconds> [<med>]:

Sends the defined MED value, or 4294967294 when unset, only at startup for the defined period in seconds, from 5-86400.

neighbor <peer>:

Enter BGP Neighbor Configuration mode.

network import-check:

Checks if a BGP network route exists in IGP before creating BGP table entries.

route-reflector allow-outbound-policy:

Allows attributes modified by route maps to be reflected.

router-id <A.B.C.D>:

Sets the router ID for the BGP daemon. This is typically set to an IP address unique to this router, and commonly is set to a local private address.

timers keep-alive <interval> hold-time <hold-time>:

Configures the intervals between keep alive messages and how long to wait for a response before considering the peer unreachable.

update-delay <delay>:

Keeps BGP in a read-only mode for the specified time after the daemon restarts or peers are cleared.

write-quanta <packets>:

Controls the size of peer update transmissions.