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-rw-r--r--doc/bird.sgml9
1 files changed, 9 insertions, 0 deletions
diff --git a/doc/bird.sgml b/doc/bird.sgml
index d2a4fc14..aeea613f 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -2405,6 +2405,15 @@ using the following configuration parameters:
malformed and corresponding BGP updates are treated as withdraws.
Default: on.
+ <tag><label id="bgp-enforce-first-as">enforce first as [<m/switch/]</tag>
+ Routes received from an EBGP neighbor are generally expected to have the
+ first (leftmost) AS number in their AS path equal to the neighbor AS
+ number. This is not enforced by default as there are legitimate cases
+ where it is not true, e.g. connections to route servers. When this
+ option is enabled, routes with non-matching first AS number are rejected
+ and corresponding updates are treated as withdraws. The option is valid
+ on EBGP sessions only. Default: off.
+
<tag><label id="bgp-enable-route-refresh">enable route refresh <m/switch/</tag>
After the initial route exchange, BGP protocol uses incremental updates
to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker