Dell N3200-ON Networking N-Series Switches User Guide version 6.8.0 - Page 1380

Communities Dell Networking BGP supports BGP standard communities as defined in RFC 1997. Dell Networking supports community lists for matching routes based on community, and supports matching and setting communities in route maps. Dell Networking BGP recognizes and honors the following wellknown communities (RFC 1997): • NO_EXPORT-A route carrying this community is not advertised to external peers. • NO_ADVERTISE-A route carrying this community is not advertised to any peer. • NO_EXPORT_SUBCONFED-A route carrying this community is not advertised to external peers. If Dell Networking receives an UPDATE message with more than 512 communities, a NOTIFICATION message is returned to the sender with error UPDATE message/attribute length error. Routing Table Overflow BGP Routing Table Device configuration errors and other network transients can cause temporary or sustained spikes in the BGP routing table size. To protect the router from allocating too much memory in these scenarios, Dell Networking BGP limits the BGP routing table size. The limit is set to the number of routes supported by the routing table (RTO). BGP imposes separate limits for each address family it supports. Once the BGP routing table is full, new routes computed in phase 2 of the decision process are not added to RTO and are not used for forwarding, but are advertised to neighbors. When the BGP routing table becomes full, a log message is written to the log warning the administrator. While BGP remains in this state, it periodically writes a log message that states the number of NLRI routes that could not be added to the routing table. BGP automatically recovers from a temporary spike in BGP routes above this limit. When BGP cannot add a route to the BGP routing table, it sets the phase 2 pending flag on that NLRI in the Accept RIB. While there are NLRI 1380 BGP