•
Commands entered at the session group level define address family-independent commands (the same
commands as in the neighbor submode).
•
Commands entered at the address family group level define address family-dependent commands for a
specified address family (the same commands as in the neighbor-address family configuration submode).
•
Commands entered at the neighbor group level define address family-independent commands and address
family-dependent commands for each address family (the same as all available neighbor commands),
and define the use command for the address family group and session group commands.
Template Inheritance Rules
In Cisco IOS XR software, BGP neighbors or groups inherit configuration from other configuration groups.
For address family-independent configurations:
•
Neighbors can inherit from session groups and neighbor groups.
•
Neighbor groups can inherit from session groups and other neighbor groups.
•
Session groups can inherit from other session groups.
•
If a neighbor uses a session group and a neighbor group, the configurations in the session group are
preferred over the global address family configurations in the neighbor group.
For address family-dependent configurations:
•
Address family groups can inherit from other address family groups.
•
Neighbor groups can inherit from address family groups and other neighbor groups.
•
Neighbors can inherit from address family groups and neighbor groups.
Configuration group inheritance rules are numbered in order of precedence as follows:
1
If the item is configured directly on the neighbor, that value is used. In the example that follows, the
advertisement interval is configured both on the neighbor group and neighbor configuration and the
advertisement interval being used is from the neighbor configuration:
RP/0/RSP0/CPU0:router(config)# router bgp 140
RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group AS_1
RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 15
RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit
RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.1.1.1
RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1
RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1
RP/0/RSP0/CPU0:router(config-bgp-nbr)# advertisement-interval 20
The following output from the show bgp neighbors command shows that the advertisement interval used
is 20 seconds:
RP/0/RSP0/CPU0:router# show bgp neighbors 10.1.1.1
BGP neighbor is 10.1.1.1, remote AS 1, local AS 140, external link
Remote router ID 0.0.0.0
BGP state = Idle
Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds
Received 0 messages, 0 notifications, 0 in queue
Sent 0 messages, 0 notifications, 0 in queue
Minimum time between advertisement runs is 20 seconds
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
22 OL-30423-03
Implementing BGP
BGP Configuration
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