Information Technology Reference
In-Depth Information
You can get a summary view of replication statistics for all update groups using the show
ip bgp replication command, as shown in Example 3-9.
Command Output for show ip bgp replication
Example 3-9
Router#show ip bgp replication
BGP Total Messages Formatted/Enqueued : 9490/0
Index Type Members Leader MsgFmt MsgRepl Csize Qsize
1 external 100 10.0.101.201 0 0 0 0
2 external 100 10.0.101.101 289 28611 4 0
3 external 9 10.0.101.10 20646 165168 0 0
4 external 91 10.0.101.1 11134 1002060 9482 0
5 internal 2 10.0.102.51 302 302 4 0
The general BGP replication statistics for the entire BGP router are provided, followed by
the statistics for each update group. The update group index and update group leader are
listed to identify the group, followed by the number of messages formatted and the number
of messages replicated. Csize and Qsize indicate how many messages are in the Update
Cache and the Update Write Queue, respectively. Nonzero values indicate that the update
group is still converging.
In contrast to the previous section about peer groups, where the replication rate was 1.54,
update group 3 in Example 3-9 has nine peers. The replication rate is 8. This shows optimal
replication. Updates were formatted for the update group leader and were replicated for all
eight of the other peers.
Update Packing Enhancement
A BGP update message consists of a BGP attribute combination followed by all the net-
work layer reachability information (NLRI) that matches that attribute combination. The
router walks through the BGP table for a certain period of time, building updates. The rout-
er transmits all the updates that have been created. This does not allow BGP to walk the
entire table each time it sends updates, because the BGP table can be huge. The NLRI found
for a particular attribute combination is not necessarily all the NLRI for that attribute com-
bination. Multiple updates need to be sent for each attribute combination. This is not the
most efficient method of handling update generation.
Cisco IOS Release 12.0(19)S brought about a significant enhancement to how Cisco IOS
handles packing NLRI into BGP update messages. The solution is to build an update cache
for each peer or update group. The NLRI for each attribute combination can then be packed
in to create a single update for each attribute combination. This provides 100% efficiency
for the update packing process and greatly reduces the number of BGP Update messages
that must be formatted and replicated.
Search WWH ::




Custom Search