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What is set community additive?
When setting community values under a route-map (set extcommunity xxxx) with the “additive” keyword, this prevents the new entry to overwrite the existing entries.
What is BGP community used for?
BGP communities (as defined in RFC 1997) are used to signal reachability information between Autonomous Systems (ASes). In principle, BGP is used to distribute routes amongst peers, but for network-managing purposes it is possible to attach additional properties to each routing update.
What is BGP community list?
A BGP community list is used to create groups of communities to use in a match clause of a route map. A community list can be used to control which routes are accepted, preferred, distributed, or advertised, for example. You can also use a community list to set, append, or modify the communities of a route.
What is no-export community?
The no-export BGP community is defined in RFC 1997: “All routes received carrying a [BGP] communities attribute containing this value MUST NOT be advertised outside a BGP confederation boundary” (i.e. outside our own AS, or across regular EBGP sessions).
What is IP community list?
The ip community-list command is used to specify a community, an extended community, or groups of both used in filtering or modifying community values. Multiple community lists for the same name can be specified to create multiple elements in the list.
What is BGP standard community?
A BGP community is an optional, transitive BGP attribute that is recognized and passed to other BGP peers. You might see a BGP community as a tag attached to the BGP routes exchanged between two BGP peers. To get started, let’s look at what a BGP community set to a route looks like in an Update message.
What is IP BGP community new-format?
A BGP community is a 32-bit number that can be included with a route. A BGP community can be displayed as a full 32-bit number (0-4,294,967,295) or as two 16-bit numbers (0-65535):(0-65535) commonly referred to as new-format. In 2006, RFC 4360 expanded BGP communities’ capabilities by providing an extended format.
What is BGP extended community?
An extended community is an 8-octet value that is also divided into two main sections. The first 2 octets of the community encode a type field while the last 6 octets carry a unique set of data in a format defined by the type field. Extended communities provide a larger range for grouping or categorizing communities.
What is BGP large community?
BGP Large Communities are a novel way to signal information between networks. Large BGP Communities are composed of three 4-byte integers, separated by a colon. This is easy to remember and accommodates advanced routing policies in relation to 4-Byte ASNs.
How are extended communities different from regular communities?
An extended community is an 8-octet value that is also divided into two main sections. The first 2 octets of the community encode a type field while the last 6 octets carry a unique set of data in a format defined by the type field. Extended communities provide a larger range for grouping or categorizing communities.
How are community values assigned to each network?
A community value is a 32-bit field that is divided into two main sections. The first 16 bits of the value encode the AS number of the network that originated the community, while the last 16 bits carry a unique number assigned by the AS. This system attempts to guarantee a globally unique set of community values for each AS in the Internet.
How are community and extended communities related in BGP?
The regular community attribute is four octets. Networking enhancements, such as VPNs, have functionality requirements that can be satisfied by an attribute such as a community. However, the 4-octet community value does not provide enough expansion and flexibility to accommodate VPN requirements. This leads to the creation of extended communities.
How are community values determined in Junos OS?
This system attempts to guarantee a globally unique set of community values for each AS in the Internet. Junos OS uses a notation of as-number:community-value, where each value is a decimal number. The AS values of 0 and 65,535 are reserved, as are all of the community values within those AS numbers.