Edge-Core AS5700-54X, Cli Reference Manual, Page: 927 / 1116

Chapter 29
| IP Routing Commands
Border Gateway Protocol (BGPv4)
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IP : NN – Community to deny or permit. The community number is
composed of a 4-byte IP address (representing the autonomous system
number) and a 2-byte network number, separated by one colon. The 2-
byte network number can range from 0 to 65535.
One or more community numbers can be entered, separated by a
space. Up to 3 community numbers are supported.
100-500 – Expanded community list number that identifies one or more
groups of communities.
expanded community-list-name – Name of expanded access list.
(Maximum length: 32 characters, no spaces or other special characters)
regular-expression – Regular expression indicating the community list
number or name. Syntax complies with the IEEE POSIX Basic Regular
Expressions (BRE) standard.
Command Mode
Global Configuration
Default Setting
No extended community lists are defined.
Command Usage
◆
Standard community lists are used to configure well-known communities or
community numbers. Expanded community lists are used to filter communities
using a regular expression.
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When multiple values are entered in the same community list, they form a
logical AND condition. When multiple values are configured in separate
community lists, the form a logical OR condition, where the first list that
matches a condition is processed.
◆
If the criteria specified for a community list is matched, then the
deny/permit condition is applied to the routing message.
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If a permit value is applied to a community list, the filter will implicitly deny
other community values.
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The route target (RT) attribute is used to identify sites that may receive routes
tagged with a specific route target. Using this attribute allows that route to be
placed in per-site forwarding tables used for routing traffic received from the
corresponding sites.
◆
The site of origin (SOO) attribute is used to identify the site from which the
provider edge (PE) router learned the route. All routes learned from a particular
site are assigned the same site of origin attribute, no matter if a site is
connected to a single PE router or multiple PE routers. Filtering based on this
extended community attribute can prevent routing loops from occurring when
a site is multi-homed.