| BGP, Border Gateway Protocol |
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Description | Glossary | RFCs | Publications | Obsolete RFCs |
| Protocol suite: | TCP/IP. |
| Protocol type: | Application layer distance vector routing protocol. |
| Port: | 179 (TCP) server. |
| SNMP MIBs: | iso.org.dod.internet.mgmt.mib-2.bgp (1.3.6.1.2.1.15). |
| Working groups: |
bgp, Border Gateway Protocol. bgpdepl, BGP Deployment and Application. bmwg, Benchmarking Methodology. idr, Inter-Domain Routing. softwire, Softwires. |
| Links: |
IANA: BGP parameters. IANA: BGP Well-Known Communities. wiki: BGP. |
BGP is an inter-Autonomous System routing protocol. The primary function of a BGP speaking system is to exchange network reachability information with other BGP systems. This network reachability information includes information on the list of Autonomous Systems that reachability information traverses. This information is sufficient for constructing a graph of AS connectivity for this reachability, from which routing loops may be pruned and, at the AS level, some policy decisions may be enforced.
BGP-1:
BGP-2:
This version removed the concept of "up",
"down", and "horizontal" relations between autonomous systems that were present in version 1.
BGP-2 introduced the concept of path attributes.
In addition, BGP-2 clarified parts of the protocol that were "under-specified".
BGP-3:
This version lifts some of the restrictions on the use of the NEXT_HOP path
attribute, and added the BGP Identifier field to the BGP OPEN message.
It also clarifies the procedure for distributing BGP routes between the BGP speakers within an autonomous system.
BGP-4:
This version redefines the previously class-based network layer
reachability portion of the updates to specify prefixes of arbitrary length in order to represent multiple classful networks in a single entry.
The AS_PATH attribute has been modified so that sets of autonomous systems, as well as individual ASs may be described.
In addition, The INTER-AS METRIC attribute has been redefined as the MULTI-EXIT DISCRIMINATOR.
The LOCAL-PREFERENCE and AGGREGATOR attributes have been added.
| MAC header | IP header | TCP header | BGP header | Data ::: |
BGP-4 header:
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Marker - - - | |||||||||||||||||||||||||||||||
| Length | Type | Data ::: | |||||||||||||||||||||||||||||
Marker. 16 bytes.
Length. 16 bits.
Type. 8 bits.
| Type | Description | References |
|---|---|---|
| 0 | ||
| 1 | OPEN. | RFC 4271 |
| 2 | UPDATE. | RFC 4271 |
| 3 | NOTIFICATION. | RFC 4271 |
| 4 | KEEPALIVE. | RFC 4271 |
| 5 | ROUTE-REFRESH. | RFC 2918 |
| 6 - 255 |
Data. Variable length.
Attributes.
| Value | Description | References |
|---|---|---|
| 0 | ||
| 1 | ORIGIN. | RFC 4271 |
| 2 | AS_PATH. | RFC 4271 |
| 3 | NEXT_HOP. | RFC 4271 |
| 4 | MULTI_EXIT_DISC. | RFC 4271, RFC 4451 |
| 5 | LOCAL_PREF. | RFC 4271 |
| 6 | ATOMIC_AGGREGATE. | RFC 4271 |
| 7 | AGGREGATOR. | RFC 4271 |
| 8 | COMMUNITY. | RFC 1997 |
| 9 | ORIGINATOR_ID. | RFC 1998, RFC 4456 |
| 10 | CLUSTER_LIST. | RFC 1998, RFC 2796, RFC 4456 |
| 11 | DPA. | |
| 12 | ADVERTISER. | RFC 1863 |
| 13 | RCID_PATH / CLUSTER_ID. | RFC 1863 |
| 14 | MP_REACH_NLRI. | RFC 2283, RFC 2858 |
| 15 | MP_UNREACH_NLRI. | RFC 2283, RFC 2858 |
| 16 | EXTENDED COMMUNITIES. | RFC 4360 |
| 17 | NEW_AS_PATH. | RFC 4893 |
| 18 | NEW_AGGREGATOR. | RFC 4893 |
| 19 | SSA, SAFI Specific Attribute. | |
| 20 | Connector Attribute. | |
| 21 | AS_PATHLIMIT (expires 27 October 2007). | |
| 22 | PMSI_TUNNEL (expires 19 June 2008). | |
| 23 | Tunnel Encapsulation Attribute. | RFC 5512 |
| 24 | Traffic Engineering. | RFC 5543 |
| 25 | IPv6 Address Specific Extended Community. | RFC 5701 |
| 26 - 254 | ||
| 255 | reserved. |
AS, Autonomous System.
AS Confederation.
(RFC 3065)
A collection of autonomous systems advertised as a single AS number to BGP speakers that are not members of the confederation.
AS Confederation Identifier.
(RFC 3065)
An externally visible autonomous system number that identifies the confederation as a whole.
Community.
A group of destinations which share some common property.
The COMMUNITIES path attribute may be used with BGP version 2 and all subsequent versions of BGP unless specifically noted otherwise.
| Community | Description |
|---|---|
| 0x00000000 - 0x0000FFFF | reserved. |
| 0x00010000 - 0xFFFEFFFF | |
| 0xFFFF0000 | reserved. |
| 0xFFFFFF01 | NO_EXPORT. All routes received carrying a communities attribute containing this value MUST NOT be advertised outside a BGP confederation boundary (a stand-alone autonomous system that is not part of a confederation should be considered a confederation itself). |
| 0xFFFFFF02 | NO_ADVERTISE. All routes received carrying a communities attribute containing this value MUST NOT be advertised to other BGP peers. |
| 0xFFFFFF03 | NO_EXPORT_SUBCONFED. All routes received carrying a communities attribute containing this value MUST NOT be advertised to external BGP peers (this includes peers in other members autonomous systems inside a BGP confederation). |
| 0xFFFFFF04 | NOPEER. This is an advisory qualification to readvertisement of a route prefix, permitting an AS not to readvertise the route prefix to all external bilateral peer neighbour AS's. It is consistent with these semantics that an AS may filter received prefixes that are received across a peering session that the receiver regards as a bilateral peer sessions. |
| 0xFFFFFF05 - 0xFFFFFFFF | reserved. |
Member-AS.
(RFC 1965)
An autonomous system that is contained in a given AS confederation.
RFCs:
[RFC 1265] BGP Protocol Analysis.
[RFC 1266] Experience with the BGP Protocol
[RFC 1267] A Border Gateway Protocol 3 (BGP-3).
[RFC 1397] Default Route Advertisement In BGP2 And BGP3 Versions Of The Border Gateway Protocol.
[RFC 1403] BGP OSPF Interaction.
[RFC 1482] Aggregation Support in the NSFNET Policy-Based Routing Database.
[RFC 1745] BGP4/IDRP for IP---OSPF Interaction.
[RFC 1772] Application of the Border Gateway Protocol in the Internet.
[RFC 1773] Experience with the BGP-4 protocol.
[RFC 1774] BGP-4 Protocol Analysis.
[RFC 1812] Requirements for IP Version 4 Routers.
[RFC 1817] CIDR and Classful Routing.
[RFC 1930] Guidelines for creation, selection, and registration of an Autonomous System (AS).
[RFC 1997] BGP Communities Attribute.
[RFC 1998] An Application of the BGP Community Attribute in Multi-home Routing.
[RFC 2042] Registering New BGP Attribute Types.
[RFC 2270] Using a Dedicated AS for Sites Homed to a Single Provider.
[RFC 2385] Protection of BGP Sessions via the TCP MD5 Signature Option.
[RFC 2439] BGP Route Flap Damping.
[RFC 2519] A Framework for Inter-Domain Route Aggregation.
[RFC 2545] Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing.
[RFC 2791] Scalable Routing Design Principles.
[RFC 2858] Multiprotocol Extensions for BGP-4.
[RFC 2918] Route Refresh Capability for BGP-4.
[RFC 3065] Autonomous System Confederations for BGP.
[RFC 3107] Carrying Label Information in BGP-4.
[RFC 3166] Request to Move RFC 1403 to Historic Status.
[RFC 3167] Request to Move RFC 1745 to Historic Status.
[RFC 3221] Commentary on Inter-Domain Routing in the Internet.
[RFC 3345] Border Gateway Protocol (BGP) Persistent Route Oscillation Condition.
[RFC 3392] Capabilities Advertisement with BGP-4.
[RFC 3765] NOPEER Community for Border Gateway Protocol (BGP) Route Scope Control.
[RFC 3882] Configuring BGP to Block Denial-of-Service Attacks.
[RFC 4098] Terminology for Benchmarking BGP Device Convergence in the Control Plane.
[RFC 4223] Reclassification of RFC 1863 to Historic.
[RFC 4264] BGP Wedgies.
[RFC 4271] A Border Gateway Protocol 4 (BGP-4).
[RFC 4272] BGP Security Vulnerabilities Analysis.
[RFC 4273] Definitions of Managed Objects for BGP-4.
[RFC 4274] BGP-4 Protocol Analysis.
[RFC 4275] BGP-4 MIB Implementation Survey.
[RFC 4276] BGP-4 Implementation Report.
[RFC 4277] Experience with the BGP-4 Protocol.
[RFC 4278] Standards Maturity Variance Regarding the TCP MD5 Signature Option (RFC 2385) and the BGP-4 Specification.
[RFC 4360] BGP Extended Communities Attribute.
[RFC 4364] BGP/MPLS IP Virtual Private Networks (VPNs).
[RFC 4365] Applicability Statement for BGP/MPLS IP Virtual Private Networks (VPNs).
[RFC 4384] BGP Communities for Data Collection.
[RFC 4451] BGP MULTI_EXIT_DISC (MED) Considerations.
[RFC 4456] BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP).
[RFC 4486] Subcodes for BGP Cease Notification Message.
[RFC 5291] Outbound Route Filtering Capability for BGP-4.
[RFC 5292] Address-Prefix-Based Outbound Route Filter for BGP-4.
[RFC 5701] IPv6 Address Specific BGP Extended Community Attribute.
[RFC 1105] A Border Gateway Protocol (BGP).
[RFC 1163] A Border Gateway Protocol (BGP).
[RFC 1164] Application of the Border Gateway Protocol in the Internet.
[RFC 1268] Application of the Border Gateway Protocol in the Internet.
[RFC 1269] Definitions of Managed Objects for the Border Gateway Protocol (Version 3).
[RFC 1364] BGP OSPF Interaction.
[RFC 1654] A Border Gateway Protocol 4 (BGP-4).
[RFC 1655] Application of the Border Gateway Protocol in the Internet.
[RFC 1656] BGP-4 Protocol Document Roadmap and Implementation Experience.
[RFC 1657] Definitions of Managed Objects for the Fourth Version of the Border Gateway Protocol (BGP-4) using SMIv2.
[RFC 1771] A Border Gateway Protocol 4 (BGP-4).
[RFC 1863] A BGP/IDRP Route Server alternative to a full mesh routing.
[RFC 1965] Autonomous System Confederations for BGP.
[RFC 1966] BGP Route Reflection. An alternative to full mesh IBGP.
[RFC 2283] Multiprotocol Extensions for BGP-4.
[RFC 2547] BGP/MPLS VPNs.
[RFC 2796] BGP Route Reflection - An Alternative to Full Mesh IBGP.
[RFC 2842] Capabilities Advertisement with BGP-4.
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Description | Glossary | RFCs | Publications | Obsolete RFCs |