The following table lists terms and definitions used in this BGP configuration discussion.
BGP Terms and Definitions
| Term | Definition |
|---|---|
| 4-octet AS numbers | A BGP extension, defined in RFC 4893, that allows for the encoding of 4-octet AS numbers. |
| aggregation | A BGP feature that provides for the aggregating of one or more specific routes into a single aggregate route, if a more specific route of the aggregate route exists in the BGP routing table. |
| AS | A set of routers under a single administration referred to as an autonomous system. |
| AS path | A BGP path attribute, used for loop detection, that provides a list of the AS numbers the route traverses. |
| BGP | The Border Gateway Protocol (BGP), defined in RFC 4271, that is the standard Exterior Gateway Protocol (EGP) for routing between administrative domains. |
| conditional advertisement | Conditional BGP announcements that are sent in addition to normal announcements, when a route specified in the configured advertise map does not exist in the configured non-exist map |
| confederation | An extension to BGP, defined in RFC 3065, which may be used to create a confederation of autonomous systems that is represented as a single autonomous system to BGP peers external to the confederation, thereby removing the "full mesh" requirement, aiding in policy administration, and reducing the management complexity of maintaining a large autonomous system. |
| graceful restart | A capability, defined in RFC 4724, that provides for the continued processing of the data-forwarding plane of a router should the control plane fail. |
| MED | The Multi-Exit Discriminator attribute used by external neighbors in the selection of the preferred path into an autonomous system (AS) that has multiple entry points. |
| multi-protocol BGP extensions | A set of BGP extensions, defined in RFC 2858, that enable BGP to carry routing information for multiple Network Layer protocols such as IPv6 and IPX. |
| outbound route filtering | A BGP capability, defined in RFC 5291, that allows a BGP speaker to send to its BGP peer a set of Outbound Route Filters (ORFs), which the peer applies in addition to its locally configured outbound filters (if any), to constrain its outbound routing updates to the speaker |
| peer group | A group of neighbors that share the same BGP attributes. |
| peer-group | A BGP capability that provides for the grouping of peers for purposes of policy, such that the group policy takes precedence for route export, and the peer configured policy takes precedence for route import. |
| route flap dampening | A BGP capability, defined in RFC 2439, that treats routes that are being announced and withdrawn at a rapid rate as unreachable, based upon a route penalty for each route withdrawal, and reachable again based upon a configurable decay over time of that route penalty. |
| route reflector | A BGP capability, defined in RFC 4456, that allows a BGP speaker (route reflector) to advertise IBGP learned routes to certain IBGP peers, relieving the scaling issue associated with a fully meshed AS. |
| route refresh | A BGP capability, defined in RFC 2918, which allows for the dynamic exchange of route refresh requests between BGP speakers and the subsequent re-advertisement of the respective Adj-RIB-Out. |
| soft reconfiguration | A BGP capability that speeds up the route installation process when an inbound policy change occurs by keeping a local copy of the routes for the specified peer or group. |
| TCP | Transmission Control Protocol. |
| TCP/MD5 authentication | A TCP extension to BGP security that defines, in RFC 2385, a TCP option for carrying an MD5 digest in a TCP segment and acts like a signature for that segment, incorporating information known only to the connection end points. |
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