Cisco Cisco IOS Software Release 12.4(11)T
BGP per Neighbor SoO Configuration
Prerequisites for BGP per Neighbor SoO Configuration
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Multiple Cisco IOS Releases
Prerequisites for BGP per Neighbor SoO Configuration
This feature assumes that a Border Gateway Protocol (BGP) network is configured and that Cisco
Express Forwarding (CEF) is enabled in your network.
Express Forwarding (CEF) is enabled in your network.
Restrictions for BGP per Neighbor SoO Configuration
A BGP neighbor or peer policy template-based SoO configuration takes precedence over the SoO value
configured in an inbound route map.
configured in an inbound route map.
Information About Configuring BGP per Neighbor SoO
Before configuring SoO values for BGP neighbors, you should understand the following concepts:
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Site of Origin BGP Community Attribute
The site-of-origin (SoO) extended community is a BGP extended community attribute that is used to
identify routes that have originated from a site so that the readvertisement of that prefix back to the
source site can be prevented. The SoO extended community uniquely identifies the site from which a
router has learned a route. BGP can use the SoO value associated with a route to prevent routing loops.
identify routes that have originated from a site so that the readvertisement of that prefix back to the
source site can be prevented. The SoO extended community uniquely identifies the site from which a
router has learned a route. BGP can use the SoO value associated with a route to prevent routing loops.
BGP per Neighbor Site of Origin Configuration
There are three ways to configure an SoO value for a BGP neighbor:
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BGP peer policy template—A peer policy template is created, and an SoO value is configured as
part of the peer policy. Under address family IPv4 VRF, a neighbor is identified and is configured
to inherit the peer policy that contains the SoO value.
part of the peer policy. Under address family IPv4 VRF, a neighbor is identified and is configured
to inherit the peer policy that contains the SoO value.
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BGP neighbor command—Under address family IPv4 VRF, a neighbor is identified, and an SoO
value is configured for the neighbor.
value is configured for the neighbor.
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BGP peer group—Under address family IPv4 VRF, a BGP peer group is configured, an SoO value
is configured for the peer group, a neighbor is identified, and the neighbor is configured as a member
of the peer group.
is configured for the peer group, a neighbor is identified, and the neighbor is configured as a member
of the peer group.
The configuration of SoO values for BGP neighbors is performed on a provider edge (PE) router, which
is the VPN entry point. When SoO is enabled, the PE router forwards prefixes to the customer premises
equipment (CPE) only when the SoO tag of the prefix does not match the SoO tag configured for the
CPE. For example, in
is the VPN entry point. When SoO is enabled, the PE router forwards prefixes to the customer premises
equipment (CPE) only when the SoO tag of the prefix does not match the SoO tag configured for the
CPE. For example, in
, an SoO tag is set as 65000:1 for the customer site that includes routers
CPE1 and CPE2 with an autonomous system number of 65000. When CPE1 sends prefixes to PE1, PE1
tags the prefixes with 65000:1, which is the SoO tag for CPE1 and CPE2. When PE1 sends the tagged
prefixes to PE2, PE2 performs a match against the SoO tag from CPE2. Any prefixes with the tag value
of 65000:1 are not sent to CPE2 because the SoO tag matches the SoO tag of CPE2, and a routing loop
is avoided.
tags the prefixes with 65000:1, which is the SoO tag for CPE1 and CPE2. When PE1 sends the tagged
prefixes to PE2, PE2 performs a match against the SoO tag from CPE2. Any prefixes with the tag value
of 65000:1 are not sent to CPE2 because the SoO tag matches the SoO tag of CPE2, and a routing loop
is avoided.