diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/bird.sgml | 44 |
1 files changed, 41 insertions, 3 deletions
diff --git a/doc/bird.sgml b/doc/bird.sgml index 174618a4..869fec1c 100644 --- a/doc/bird.sgml +++ b/doc/bird.sgml @@ -2161,6 +2161,7 @@ avoid routing loops. <item> <rfc id="6286"> - AS-Wide Unique BGP Identifier <item> <rfc id="6608"> - Subcodes for BGP Finite State Machine Error <item> <rfc id="6793"> - BGP Support for 4-Octet AS Numbers +<item> <rfc id="7311"> - Accumulated IGP Metric Attribute for BGP <item> <rfc id="7313"> - Enhanced Route Refresh Capability for BGP <item> <rfc id="7606"> - Revised Error Handling for BGP UPDATE Messages <item> <rfc id="7911"> - Advertisement of Multiple Paths in BGP @@ -2739,6 +2740,36 @@ be used in explicit configuration. TX direction. When active, all available routes accepted by the export filter are advertised to the neighbor. Default: off. + <tag><label id="bgp-aigp">aigp <m/switch/|originate</tag> + The BGP protocol does not use a common metric like other routing + protocols, instead it uses a set of criteria for route selection + consisting both overall AS path length and a distance to the nearest AS + boundary router. Assuming that metrics of different autonomous systems + are incomparable, once a route is propagated from an AS to a next one, + the distance in the old AS does not matter. + + The AIGP extension (<rfc id="7311">) allows to propagate accumulated + IGP metric (in the AIGP attribute) through both IBGP and EBGP links, + computing total distance through multiple autonomous systems (assuming + they use comparable IGP metric). The total AIGP metric is compared in + the route selection process just after Local Preference comparison (and + before AS path length comparison). + + This option controls whether AIGP attribute propagation is allowed on + the session. Optionally, it can be set to <cf/originate/, which not only + allows AIGP attribute propagation, but also new AIGP attributes are + automatically attached to non-BGP routes with valid IGP metric (e.g. + <cf/ospf_metric1/) as they are exported to the BGP session. Default: + enabled for IBGP (and intra-confederation EBGP), disabled for regular + EBGP. + + <tag><label id="bgp-cost">cost <m/number/</tag> + When BGP <ref id="bgp-gateway" name="gateway mode"> is <cf/recursive/ + (mainly multihop IBGP sessions), then the distance to BGP next hop is + based on underlying IGP metric. This option specifies the distance to + BGP next hop for BGP sessions in direct gateway mode (mainly direct + EBGP sessions). + <tag><label id="bgp-graceful-restart-c">graceful restart <m/switch/</tag> Although BGP graceful restart is configured mainly by protocol-wide <ref id="bgp-graceful-restart" name="options">, it is possible to @@ -2807,9 +2838,11 @@ some of them (marked with `<tt/O/') are optional. presence of which indicates that the route has been aggregated from multiple routes by some router on the path from the originator. -<!-- we don't handle aggregators right since they are of a very obscure type - <tag>bgp_aggregator</tag> ---> + <tag><label id="rta-bgp-aggregator">void bgp_aggregator [O]</tag> + This is an optional attribute specifying AS number and IP address of the + BGP router that created the route by aggregating multiple BGP routes. + Currently, the attribute is not accessible from filters. + <tag><label id="rta-bgp-community">clist bgp_community [O]</tag> List of community values associated with the route. Each such value is a pair (represented as a <cf/pair/ data type inside the filters) of 16-bit @@ -2844,6 +2877,11 @@ some of them (marked with `<tt/O/') are optional. <tag><label id="rta-bgp-cluster-list">clist bgp_cluster_list [I, O]</tag> This attribute contains a list of cluster IDs of route reflectors. Each route reflector prepends its cluster ID when reflecting the route. + + <tag><label id="rta-bgp-aigp">void bgp_aigp [O]</tag> + This attribute contains accumulated IGP metric, which is a total + distance to the destination through multiple autonomous systems. + Currently, the attribute is not accessible from filters. </descrip> <sect1>Example |