Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

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This feature assumes that a Border Gateway Protocol (BGP) network is configured and that Cisco Express Forwarding is enabled in your network.

A BGP neighbor or peer policy template-based SoO configuration takes precedence over the SoO value configured in an inbound route map.

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.

A route distinguisher (RD) creates routing and forwarding tables and specifies the default route distinguisher for a VPN. The RD is added to the beginning of an IPv4 prefix to change it into a globally unique VPN-IPv4 prefix. An RD can be composed in one of two ways: with an autonomous system number and an arbitrary number or with an IP address and an arbitrary number.

You can enter an RD in either of these formats:

• Enter a 16-bit autonomous system number, a colon, and a 32-bit number. For example:

45000:3

• Enter a 32-bit IP address, a colon, and a 16-bit number. For example:

192.168.10.15:1

There are three ways to configure an SoO value for a BGP neighbor:

• 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.

• BGP neighbor command--Under address family IPv4 VRF, a neighbor is identified, and an SoO value is configured for the neighbor.

• 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.

Note	A BGP neighbor or peer policy template-based SoO configuration takes precedence over the SoO value configured in an inbound route map.

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 the figure below, 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.

Figure 1. Network Diagram for SoO Example

In releases prior to the introduction of this feature, the SoO extended community attribute is configured using an inbound route map that sets the SoO value during the update process. With the introduction of the BGP per Neighbor Site of Origin feature, two new commands configured in submodes under router configuration mode simplify the SoO value configuration.

1.    enable


2.    configure terminal


3.    ip cef


4.    ip vrf vrf-name


5.    rd route-distinguisher


6.    route-target {export | both} route-target-ext-community


7.    route-target {import | both} route-target-ext-community


8.    exit


9.    interface type number


10.    ip vrf forwarding vrf-name [downstream vrf-name2]


11.    ip address ip-address mask [secondary]


12.    end


13.    show ip vrf [brief | detail | interfaces | id] [vrf-name] [output-modifiers]

Device> enable

Device# configure terminal

Device(config)# ip cef

Device(config)# ip vrf SOO_VRF

Device(config-vrf)# rd 1:1

Device(config-vrf)# route-target export 1:1

Device(config-vrf)# route-target import 1:1

Device(config-vrf)# exit

Device(config)# interface GigabitEthernet 1/0/0

Device(config-if)# ip vrf forwarding SOO_VRF

Device(config-if)# ip address 192.168.1.2 255.255.255.0

Device(config-if)# end

Device# show ip vrf

Device# show ip vrf

Name                             Default RD            Interfaces
SOO_VRF                                 1:1                GE1/0/0

Perform this task on router PE1 in the figure above to configure an SoO value for a BGP neighbor at the router CPE1 in the figure above using a peer policy template. In this task, a peer policy template is created, and the SoO value is configured for 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.

For a configuration example involving 4-byte autonomous system numbers, see the “Example: Configuring a per Neighbor SoO Value with a 4-Byte AS Number Using a BGP Peer Policy Template” section.

Note

If a BGP peer inherits from several peer policy templates that specify different SoO values, the SoO value in the last template applied takes precedence and is applied to the peer. However, direct configuration of the SoO value on the BGP neighbor overrides any inherited template configurations of the SoO value.

1.    enable


2.    configure terminal


3.    router bgp autonomous-system-number


4.    address-family ipv4 [unicast | multicast | vrf vrf-name]


5.    neighbor {ip-address | peer-group-name} remote-as autonomous-system-number


6.    neighbor ip-address activate


7.    neighbor {ip-address | peer-group-name} soo extended-community-value


8.    end

Device> enable

Device# configure terminal

Device(config)# router bgp 50000

Device(config-router)# address-family ipv4 vrf SOO_VRF

Device(config-router-af)# neighbor 192.168.2.1 remote-as 65000

Device(config-router-af)# neighbor 192.168.2.1 activate

Device(config-router-af)# neighbor 192.168.2.1 soo 65000:1

Device(config-router-af)# end

Before You Begin

This task assumes that the task described in “Enabling Cisco Express Forwarding and Configuring VRF Instances” has been performed.

Note	A BGP peer cannot inherit from a peer policy or session template and be configured as a peer group member at the same. BGP templates and BGP peer groups are mutually exclusive.

1.    enable


2.    configure terminal


3.    router bgp autonomous-system-number


4.    address-family ipv4 [unicast | multicast | vrf vrf-name]


5.    neighbor peer-group-name peer-group


6.    neighbor {ip-address | peer-group-name} soo extended-community-value


7.    neighbor ip-address remote-as autonomous-system-number


8.    neighbor ip-address activate


9.    neighbor ip-address peer-group peer-group-name


10.    end

Device> enable

Device# configure terminal

Device(config)# router bgp 50000

Device(config-router)# address-family ipv4 vrf SOO_VRF

Device(config-router-af)# neighbor SOO_group peer-group

Device(config-router-af)# neighbor SOO_group soo 65000:1

Device(config-router-af)# neighbor 192.168.1.1 remote-as 65000

Device(config-router-af)# neighbor 192.168.1.1 activate

Device(config-router-af)# neighbor 192.168.1.1 peer-group SOO_group

Device(config-router-af)# end

The following example shows how to create a peer policy template and configure an SoO value as part of the peer policy. After enabling Cisco Express Forwarding and configuring a VRF instance named SOO_VRF, a peer policy template is created and an SoO value is configured as part of the peer policy. Under the IPv4 VRF address family, a neighbor is identified and configured to inherit the peer policy that contains the SoO value.

ip cef
ip vrf SOO_VRF
 rd 1:1
 route-target export 1:1
 route-target import 1:1
 exit
interface GigabitEthernet 1/0/0
 ip vrf forwarding SOO_VRF
 ip address 192.168.1.2 255.255.255.0
 exit
router bgp 50000
 template peer-policy SOO_POLICY
  soo 65000:1
  exit-peer-policy
 address-family ipv4 vrf SOO_VRF
  neighbor 192.168.1.1 remote-as 65000
  neighbor 192.168.1.1 activate
  neighbor 192.168.1.1 inherit peer-policy SOO_POLICY
  end

The following example shows how to create a peer policy template and configure an SoO value using a 4-byte autonomous system number, 1.2 in asdot format, as part of the peer policy. Under the IPv4 VRF address family, a neighbor is identified and configured to inherit the peer policy that contains the SoO value.

router bgp 1.2
 template peer-policy SOO_POLICY
  soo 1.2:3
  exit-peer-policy
 address-family ipv4 vrf SOO_VRF
  neighbor 192.168.3.2 remote-as 1.14
  neighbor 192.168.3.2 activate
  neighbor 192.168.3.2 inherit peer-policy SOO_POLICY
  end

The following example shows how to create a peer policy template and configure an SoO value using a 4-byte autonomous system number, 65538 in asplain format, as part of the peer policy. Under the IPv4 VRF address family, a neighbor is identified and configured to inherit the peer policy that contains the SoO value.

router bgp 65538
 template peer-policy SOO_POLICY
  soo 65538:3
  exit-peer-policy
 address-family ipv4 vrf SOO_VRF
  neighbor 192.168.3.2 remote-as 65550
  neighbor 192.168.3.2 activate
  neighbor 192.168.3.2 inherit peer-policy SOO_POLICY
  end

The following example shows how to configure an SoO value for a BGP neighbor. After enabling Cisco Express Forwarding and configuring a VRF instance named SOO_VRF, a neighbor is identified in the IPv4 VRF address family and an SoO value is configured for the neighbor.

ip cef
ip vrf SOO_VRF
 rd 1:1
 route-target export 1:1
 route-target import 1:1
 exit
interface GigabitEthernet 1/0/0
 ip vrf forwarding SOO_VRF
 ip address 192.168.2.2 255.255.255.0
 exit
router bgp 50000
 address-family ipv4 vrf SOO_VRF
  neighbor 192.168.2.1 remote-as 65000
  neighbor 192.168.2.1 activate
  neighbor 192.168.2.1 soo 65000:1
  end

The following example shows how to configure an SoO value for a BGP neighbor. In this example, all BGP neighbors, route targets, and SoO values use 4-byte autonomous system numbers in asplain format. After checking that CEF is enabled, a VRF instance named SOO_VRF is configured with route targets. In a BGP router session, a neighbor is configured in the IPv4 VRF address family, and an SoO value is configured for the neighbor.

show ip cef
ip vrf SOO_VRF
 rd 100:200
 route-target export 1.14:1
 route-target import 1.14:1
 exit
interface Ethernet 1/0
 ip vrf forwarding SOO_VRF
 ip address 192.168.2.2 255.255.255.0
 exit
router bgp 1.2
 address-family ipv4 vrf SOO_VRF
  neighbor 192.168.2.1 remote-as 1.14
  neighbor 192.168.2.1 activate
  neighbor 192.168.2.1 soo 1.14:1
  end

The following example shows how to configure an SoO value for a BGP peer group. After enabling Cisco Express Forwarding and configuring a VRF instance named SOO_VRF, a BGP peer group is configured in the IPv4 VRF address family, 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.

ip cef
ip vrf SOO_VRF
 rd 1:1
 route-target export 1:1
 route-target import 1:1
 exit
interface GigabitEthernet 1/0/0
 ip vrf forwarding SOO_VRF
 ip address 192.168.1.2 255.255.255.0
 exit
router bgp 50000
 address-family ipv4 vrf SOO_VRF
  neighbor SOO_GROUP peer-group
  neighbor SOO_GROUP soo 65000:65
  neighbor 192.168.1.1 remote-as 65000
  neighbor 192.168.1.1 activate
  neighbor 192.168.1.1 peer-group SOO_GROUP 
  end