Vyatta Network OS Documentation

Learn how to install, configure and operate the Vyatta NOS, which helps drive our virtual networking & physical platforms portfolio.

protocols bgp <asn> parameters maximum-paths ibgp <max-paths>

Specifies the maximum number of iBGP paths to a destination.

set protocols bgp asn parameters maximum-paths ibgp max-paths
delete protocols bgp asn parameters maximum-paths ibgp [ max-paths ]
show protocols bgp asn parameters maximum-paths ibgp

A single iBGP path can be inserted into the routing table.

asn
The number for the AS in which this router resides. The numbers range from 1 through 4294967294. The subrange, 64512 through 65534, is reserved for private AS.
max-paths
The maximum number of iBGP paths to a destination to be inserted in the routing table. The numbers range from 2 through 64, where 1 indicates that a single path can be inserted into the routing table. This has the same effect as not configuring the maximum-paths feature.

Configuration mode


protocols {
    bgp asn {
        parameters {
            maximum-paths {
                ibgp max-paths 
            }
        }
    }
}

Use this command to specify the maximum number of iBGP paths to a destination to allow in the routing table. Normally, the single best path is determined and then added to the routing table. This command allows more than one path to be added to the routing table.

To be considered as one of a set of multipaths to a destination, candidate paths must have identical weight, LOCAL PREFERENCE, AS PATH LENGTH, ORIGIN, MULTI_EXIT_DISC (MED), and AS_PATH.

Once the paths are selected, traffic load is shared across them on a per session basis. That is, each new session is routed across the path that has the fewest active sessions. To achieve this, the route is advertised with the nexthop address being the interface address rather than the address of the best path. Once traffic is routed to the interface, it can select the path based on current traffic loads.

The attribute set for the advertised route is based on the attribute set from the best path, with the following attributes aggregated from the multipaths, including the best path: AS_PATH, ORIGIN, COMMUNITIES, and EXTENDED COMMUNITIES.

If the deterministic MED option is configured (see protocols bgp <asn> parameters deterministic-med), a set of multipaths is dervied for each peer AS. The set of paths for the peer AS associated with the selected best path are added to the routing table.

If the always-compare MED option is configured (see protocols bgp <asn> parameters always-compare-med), the MED is compared across all paths from all AS. The set of multipaths can be distributed across AS.

Note: Since each path requires additional memory and processing resources, the number of maximum-paths should be kept to a minimum. This is especially true for large routing tables.
Note: The multipath feature is only supported in IPv4 unicast environments.

Use the set form of this command to specify the maximum number of paths to a destination.

Use the delete form of this command to remove the configuration and allow only a single best path to a destination in the routing table.

Use the show form of this command to view iBGP maximum path configuration settings.