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Diffstat (limited to 'doc/bird.sgml')
| -rw-r--r-- | doc/bird.sgml | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/doc/bird.sgml b/doc/bird.sgml index ae308d4c..b4d9ea4e 100644 --- a/doc/bird.sgml +++ b/doc/bird.sgml @@ -1618,9 +1618,7 @@ regarded as empty bgppath/*clist for most purposes. The optional attribute that can be used to specify a distance to the network for routes that do not have a native protocol metric attribute (like <cf/ospf_metric1/ for OSPF routes). It is used mainly by BGP to - compare internal distances to boundary routers (see below). It is also - used when the route is exported to OSPF as a default value for OSPF type - 1 metric. + compare internal distances to boundary routers (see below). </descrip> <p>There also exist protocol-specific attributes which are described in the @@ -3536,8 +3534,15 @@ protocol ospf [v2|v3] <name> { with internal <cf/metric/, a <cf/metric of type 2/ is always longer than any <cf/metric of type 1/ or any <cf/internal metric/. <cf/Internal metric/ or <cf/metric of type 1/ is stored in attribute <cf/ospf_metric1/, <cf/metric type -2/ is stored in attribute <cf/ospf_metric2/. If you specify both metrics only -metric1 is used. +2/ is stored in attribute <cf/ospf_metric2/. + +When both metrics are specified then <cf/metric of type 2/ is used. This is +relevant e.g. when a type 2 external route is propagated from one OSPF domain to +another and <cf/ospf_metric1/ is an internal distance to the original ASBR, +while <cf/ospf_metric2/ stores the type 2 metric. Note that in such cases if +<cf/ospf_metric1/ is non-zero then <cf/ospf_metric2/ is increased by one to +ensure monotonicity of metric, as internal distance is reset to zero when an +external route is announced. <p>Each external route can also carry attribute <cf/ospf_tag/ which is a 32-bit integer which is used when exporting routes to other protocols; otherwise, it |