Command:

set extcommunity


Mode:

Router(config-route-map)#


Syntax:

set extcommunity {rt extended-community-value [additive] | soo extended-community-value}
no set extcommunity {rt extended-community-value [additive] | soo extended-community-value}

 

Syntax Description:

rt Specifies the route target (RT) extended community attribute.
soo Specifies the site of origin (SOO) extended community attribute.
extended-community-value Specifies the value to be set. The value can be one of the following combinations:

autonomous-system-number:network-number
ip-address:network-number

The colon is used to separate the autonomous system number and network number or IP address and network number.

additive (Optional) Adds a route target to the existing route target list without replacing any existing route targets.

 

Command Description:

To set Border Gateway Protocol (BGP) extended community attributes, use the set extcommunity command in route-map configuration mode. To delete the entry, use the no form of this command.

Defaults:

Specifying new route targets with the rt keyword replaces existing route targets by default, unless the additive keyword is used. The use of the additive keyword adds the new route target to the existing route target list but does not replace any existing route targets.

Extended community attributes are used to configure, filter, and identify routes for virtual routing and forwarding instances (VRFs) and Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs).

The set extcommunity command is used to configure set clauses that use extended community attributes in route maps. All of the standard rules of match and set clauses apply to the configuration of extended community attributes.

The route target (RT) extended community attribute is configured with the rt keyword. This attribute is used to identify a set of sites and VRFs that may receive routes that are tagged with the configured route target. Configuring the route target extended attribute with a route allows that route to be placed in the per-site forwarding tables that are used for routing traffic that is received from corresponding sites.

The site of origin (SOO) extended community attribute is configured with the soo keyword. This attribute uniquely identifies the site from which the Provider Edge (PE) router learned the route. All routes learned from a particular site must be assigned the same SOO extended community attribute, whether a site is connected to a single PE router or multiple PE routers. Configuring this attribute prevents routing loops from occurring when a site is multihomed. The SOO extended community attribute is configured on the interface and is propagated into BGP through redistribution. The SOO can be applied to routes that are learned from VRFs. The SOO should not be configured for stub sites or sites that are not multihomed.


Example:

The following example sets the route target to extended community attribute 100:2 for routes that are permitted by the route map:

Router(config)# access-list 2 permit 192.168.78.0 255.255.255.0
Router(config)# route-map MAP_NAME permit 10
Router(config-route-map)# match ip-address 2
Router(config-route-map)# set extcommunity rt 100:2

The following example sets the route target to extended community attribute 100:3 for routes that are permitted by the route map. The use of the additive keyword adds route target 100:3 to the existing route target list but does not replace any existing route targets.

Router(config)# access-list 3 permit 192.168.79.0 255.255.255.0
Router(config)# route-map MAP_NAME permit 10
Router(config-route-map)# match ip-address 3
Router(config-route-map)# set extcommunity rt 100:3 additive

The following example sets the site of origin to extended community attribute 100:4 for routes that are permitted by the route map:

Router(config)# access-list 4 permit 192.168.80.0 255.255.255.0
Router(config)# route-map MAP_NAME permit 10
Router(config-route-map)# match ip-address 4
Router(config-route-map)# set extcommunity soo 100:4


Misconceptions:

Configuring route targets with the set extcommunity command will replace existing route targets, unless the additive keyword is used.


Related Commands:

match extcommunity
route-map
show ip extcommunity-list
show route-map

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