bgp

Configures BGP (Border Gateway Protocol) settings

BGP is an inter-ISP routing protocol which establishes routing between ISPs (Internet Service Providers). ISPs use BGP to exchange routing and reachability information between AS (Autonomous Systems) on the Internet. BGP makes routing decisions based on paths, network policies and/or rules configured by network administrators. The primary role of a BGP system is to exchange network reachability information with other BGP peers. This information includes information on AS that the reachability information traverses. This information is sufficient to create a graph of AS connectivity from which routing decisions can be created and rules enforced.

An AS is a set of routers under the same administration that use IGP (Interior Gateway Protocol) and common metrics to define how to route packets within the AS. AS uses inter-AS routing to route packets to other ASs. For an external AS, an AS appears to have a single coherent interior routing plan and presents a consistent picture of the destinations reachable through it.

Routing information exchanged through BGP supports only destination based forwarding (it assumes a router forwards packets based on the destination address carried in the IP header of the packet).

BGP uses TCP as its transport protocol. This eliminates the need to implement explicit update fragmentation, retransmission, acknowledgment, and sequencing. BGP listens on TCP port 179. The error notification mechanism used in BGP assumes that TCP supports a graceful close (all outstanding data is delivered before the connection is closed).

Supported on the following devices:

Syntax

bgp [as-path-list|community-list|extcommunity-list|ip-access-list|ip-prefix-list] <LIST-NAME>

Parameters

bgp [as-path-list|community-list|extcommunity-list|ip-access-list|ip-prefix-list] <LIST-NAME>
as-path-list <LIST-NAME> Creates an AS path list and enters its configuration mode
  • <LIST-NAME> – Provide the AS-PATH-LIST name.
community-list <LIST-NAME> Creates a community list and enters its configuration mode
  • <LIST-NAME> – Provide the COMMUNITY-LIST name.
extcommunity-list <LIST-NAME> Creates an extended community list and enters its configuration mode
  • <LIST-NAME> – Provide the EXTCOMMUNITY-LIST name.
ip-access-list <LIST-NAME> Creates a BGP IP access list and enters its configuration mode
  • <LIST-NAME> – Provide the BGP IP-ACCESS-LIST name.
ip-prefix-list <LIST-NAME> Creates a BGP IP prefix list and enters its configuration mode
  • <LIST-NAME> – Provide the BGP IP-PREFIX-LIST name.

Examples

nx9500-6C8809(config)#bgp ?
  as-path-list       BGP AS path list Configuration
  community-list     Add a community list entry
  extcommunity-list  Add a extended community list entry (EXPERIMENTAL)
  ip-access-list     Add an access list entry
  ip-prefix-list     Build a prefix list

nx9500-6C8809(config)#
nx9500-6C8809(config)#bgp as-path-list AS-TEST-PATH
nx9500-6C8809(config-bgp-as-path-list-AS-TEST-PATH)#?
BGP AS Path List Mode commands:
  deny     Specify packets to reject
  no       Negate a command or set its defaults
  permit   Specify packets to forward

  clrscr   Clears the display screen
  commit   Commit all changes made in this session
  do       Run commands from Exec mode
  end      End current mode and change to EXEC mode
  exit     End current mode and down to previous mode
  help     Description of the interactive help system
  revert   Revert changes
  service  Service Commands
  show     Show running system information
  write    Write running configuration to memory or terminal

nx9500-6C8809(config-bgp-as-path-list-AS-TEST-PATH)#

Related Commands

no Modifies BGP settings, based on the parameters passed
Note

Note

For more information on the association-acl-policy, see Border Gateway Protocol.
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