HPE 5800 Series Configuration Manual page 183

Figure 60 LOCAL_PREF attribute
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COMMUNITY
The COMMUNITY attribute identifies the community of BGP routes. A BGP community is a
group of routes with the same characteristics. It has no geographical boundaries. Routes of
different ASs can belong to the same community.
A route can carry one or more COMMUNITY attribute values (each of which is represented by a
four-byte integer). The receiving router processes the route (for example, determining whether
to advertise the route and the scope for advertising the route) based on the COMMUNITY
attribute values rather than complex filtering rules (for example, ACLs). This simplifies routing
policy usage and facilitates management and maintenance.
Well-known community attributes involve the following:
INTERNET—By default, all routes belong to the Internet community. Routes with this
attribute can be advertised to all BGP peers.
NO_EXPORT—After received, routes with this attribute cannot be advertised out of the
local AS or out of the local confederation, but can be advertised to other sub-ASs in the
confederation. For confederation information, see
BGP networks."
NO_ADVERTISE—After received, routes with this attribute cannot be advertised to other
BGP peers.
NO_EXPORT_SUBCONFED—After received, routes with this attribute cannot be
advertised out of the local AS or other sub-ASs in the local confederation.
You can configure community lists based on the BGP community attribute to filter BGP routes.
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Extended community attribute
To satisfy increasing user demands, BGP defines a new attribute, the extended community
attribute. The extended community attribute has the following advantages over the community
attribute:
Provides more attribute values by extending the attribute length to eight bytes.
Allows for using different types of extended community attributes in different scenarios to
enhance route filtering and control and simplify configuration and management.
You can select an extended community attribute type as needed to implement route filtering
and control. This simplifies configuration and management.
"Settlements for problems in large-scale
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