"no bgp default ipv4-unicast" command

Unanswered Question
Apr 15th, 2009

What is the use of

"no bgp default ipv4-unicast" command ?

As per my info by default router exchange IPv4 prefixes.To change this default behavour we have to option to exchange vpnv4 prefies=>

1.Use of "no bgp default ipv4-unicast" command.

2.configure BGP neighbour under BGP and activate the same for in VPNv4 address fanily.

Is this correct ?

I have this problem too.
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Giuseppe Larosa Wed, 04/15/2009 - 04:44

Hello Ganpat,

the meaning of the command is to prepare the router to be multiprotocol and not only to advertise ipv4 unicast address family that is the default.

So no bgp default ipv4-unicast

means = be multi address-families oriented and check the neighbor activate command in each AF context to see on what address families each neighbor has to be contacted/consulted.

During BGP session setup the capabilities exchange tells on what "channels/arguments" the local node would like to talk with the peer.

For this reason when giving the command all existing BGP sessions are reset to perform capabilities negotiation.

May be in newer IOS images you can reach the AF configuration without using the commanf but in the past it was mandatory to achieve multi-protocol BGP operation.



Hope to help


petersrule2003 Sat, 04/30/2011 - 02:33

Hi Giuseppe

I dont entirely agree , the command just disables ipv4 unicast address family peering capability , the router is multiprotocol whether you enable or disable this command . you may have a scenario where you dont want to receive  full internet or ipv4 bgp  routes e.g MPLS PE node


Giuseppe Larosa Wed, 05/04/2011 - 02:29

Hello Petersrule2003,

the behaviour may have changed over time in newer IOS images

>> the command just disables ipv4 unicast address family peering capability


the command reference


still provides

Command Default

IPv4 address family routing information is advertised by default for each BGP routing session configured with the neighbor remote-as command, unless you first configure the no bgp default ipv4-unicast command before configuring the neighbor remote-as command.

we need to go a step further sometimes then command reference

hope to help



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