protocols bgp <asn> parameters maximum-paths ebgp <max-paths>
Specifies the maximum number of eBGP paths to a destination.
A single eBGP 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 eBGP 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 {
ebgp max-paths
}
}
}
}Use this command to specify the maximum number of eBGP 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 PEER AS.
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 from one AS to another.
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 eBGP maximum path configuration settings.