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Implementing BGP on Cisco IOS XR Software
How to Implement BGP on Cisco IOS XR Software
RC-108
Cisco IOS XR Routing Configuration Guide
OL-14356-01
Step 14
address-family {ipv4 {unicast |
labeled-unicast} | ipv6 unicast}
Example:
RP/0/RP0/CPU0:router(config-bgp-vrf-nbr)#
address-family ipv4 unicast
Enables an address family for the CE peer.
Step 15
site-of-origin [as-number:nn | ip-address:nn]
Example:
RP/0/RP0/CPU0:router(config-bgp-vrf-nbr-af)#
site-of-origin 234:111
Configures the site-of-origin (SoO) extended community.
Routes that are learned from this CE neighbor are tagged
with the SoO extended community before being advertised
to the rest of the PEs. SoO is frequently used to detect loops
when as-override is configured on the PE router. If the
prefix is looped back to the same site, the PE detects this
and does not send the update to the CE.
Step 16
as-override
Example:
RP/0/RP0/CPU0:router(config-bgp-vrf-nbr-af)#
as-override
Configures AS override on the PE router. This causes the PE
router to replace the CE’s ASN with its own (PE) ASN.
Note This loss of information could lead to routing loops;
to avoid loops caused by as-override, use it in
conjunction with site-of-origin.
Step 17
allowas-in [as-occurrence-number]
Example:
RP/0/RP0/CPU0:router(config-bgp-vrf-nbr-af)#
allowas-in 5
Allows an AS path with the PE autonomous system number
(ASN) a specified number of times.
Hub and spoke VPN networks need the looping back of
routing information to the HUB PE through the HUB CE.
When this happens, due to the presence of the PE ASN, the
looped-back information is dropped by the HUB PE. To
avoid this, use the allowas-in command to allow prefixes
even if they have the PEs ASN up to the specified number
of times.
Step 18
route-policy route-policy-name in
Example:
RP/0/RP0/CPU0:router(config-bgp-vrf-nbr-af)#
route-policy pe_ce_in_policy in
Specifies a routing policy for an inbound route. The policy
can be used to filter routes or modify route attributes.
Command or Action Purpose