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-rw-r--r--doc/bird.sgml18
1 files changed, 11 insertions, 7 deletions
diff --git a/doc/bird.sgml b/doc/bird.sgml
index bcf1c8fb..fc5fc9ae 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -1804,13 +1804,17 @@ using the following configuration parameters:
other means. Default: 0 (no local AS number allowed).
<tag>enable route refresh <m/switch/</tag>
- When BGP speaker changes its import filter, it has to re-examine all
- routes received from its neighbor against the new filter. As these
- routes might not be available, there is a BGP protocol extension Route
- Refresh (specified in RFC 2918) that allows BGP speaker to request
- re-advertisement of all routes from its neighbor. This option specifies
- whether BIRD advertises this capability and accepts such requests. Even
- when disabled, BIRD can send route refresh requests. Default: on.
+ After the initial route exchange, BGP protocol uses incremental updates
+ to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker
+ changes its import filter, or if there is suspicion of inconsistency) it
+ is necessary to do a new complete route exchange. BGP protocol extension
+ Route Refresh (RFC 2918) allows BGP speaker to request re-advertisement
+ of all routes from its neighbor. BGP protocol extension Enhanced Route
+ Refresh (RFC 7313) specifies explicit begin and end for such exchanges,
+ therefore the receiver can remove stale routes that were not advertised
+ during the exchange. This option specifies whether BIRD advertises these
+ capabilities and supports related procedures. Note that even when
+ disabled, BIRD can send route refresh requests. Default: on.
<tag>graceful restart <m/switch/|aware</tag>
When a BGP speaker restarts or crashes, neighbors will discard all