COMMUNITIES path attribute is an optional transitive attribute as described in RFC1997。 But in IOS by default, BGP community attributes are not advertised to peers. The neighbor send-community command enables the sending of BGP community attributes t...

As OSPF suggested "virtual link" is used to link a area isn't connected bankbone area 0 by physical connection or link a bankbone area 0 by partitioned. I meeted a situation, a area have tow routers connected area 0 ABRs through two links. The area w...