BigIron RX Series Configuration Guide 77753-1001810-01Configuring a BGP4 peer group 26Peer group parametersYou can set all neighbor parameters in a peer group. When you add a neighbor to the peer group,the neighbor receives all the parameter settings you set in the group, except parameter values youhave explicitly configured for the neighbor. If you do not set a neighbor parameter in the peer groupand the parameter also is not set for the individual neighbor, the neighbor uses the default value.Configuration rulesThe following rules apply to peer group configuration:• You must configure a peer group before you can add neighbors to the peer group.• If you remove a parameter from a peer group, the value for that parameter is reset to thedefault for all the neighbors within the peer group, unless you have explicitly set that parameteron individual neighbors. In this case, the value you set on the individual neighbors applies tothose neighbors, while the default value applies to neighbors for which you have not explicitlyset the value.NOTEIf you enter a command to remove the remote AS parameter from a peer group, the softwarechecks to ensure that the peer group does not contain any neighbors. If the peer group doescontain neighbors, the software does not allow you to remove the remote AS. The softwareprevents removing the remote AS in this case so that the neighbors in the peer group that areusing the remote AS do not lose connectivity to the BigIron RX.You can override neighbor parameters on an individual neighbor basis:• If you do not specify a parameter for an individual neighbor, the neighbor uses the value in thepeer group.• If you set the parameter for the individual neighbor, that value overrides the value you set inthe peer group.• If you add a parameter to a peer group that already contains neighbors, the parameter value isapplied to neighbors that do not already have the parameter explicitly set. If a neighbor hasthe parameter explicitly set, the explicitly set value overrides the value you set for the peergroup.• If you remove the setting for a parameter from a peer group, the value for that parameterchanges to the default value for all the neighbors in the peer group that do not have thatparameter individually set.Configuring a peer groupTo configure a peer group, enter commands such as the following at the BGP configuration level.BigIron RX(config-bgp)# neighbor PeerGroup1 peer-groupBigIron RX(config-bgp)# neighbor PeerGroup1 description “EastCoast Neighbors”BigIron RX(config-bgp)# neighbor PeerGroup1 remote-as 100BigIron RX(config-bgp)# neighbor PeerGroup1 distribute-list out 1The commands in this example configure a peer group called “PeerGroup1” and set the followingparameters for the peer group:• A description, “EastCoast Neighbors”• A remote AS number, 100
