Open links in new tab
  1. Cisco Press
    https://www.ciscopress.com/articles/article.asp?p=2756480&seqNum=4

    BGP Neighbor States > BGP Fundamentals | Cisco Press

    • This is the first stage of the BGP FSM. BGP detects a start event, tries to initiate a TCP connection to the BGP peer, and also listens for a new connect from a peer router. If an error causes BGP to go back t… See more

    Connect

    In this state, BGP initiates the TCP connection. If the 3-way TCP handshake completes, the established BGP Session BGP process resets the … See more

    Cisco Press
    Active

    In this state, BGP starts a new 3-way TCP handshake. If a connection is … See more

    Cisco Press
    Opensent

    In this state, an Open message has been sent from the originating router and is awaiting an Open message from the other router. After the originating router receives the OPEN … See more

    Cisco Press
    Openconfirm

    In this state, BGP waits for a Keepalive or Notification message. Upon receipt of a neighbor’s Keepalive, the state is moved to Established. If the hold timer expires, a stop event occur… See more

    Cisco Press
    Feedback
    Table of Contents
    Connect
    Active
    Opensent
    Openconfirm
     
  1. Just like OSPF or EIGRP, BGP establishes a neighbor adjacency with other BGP routers before they exchange any routing information. Unlike other routing protocols however, BGP does not use broadcast or multicast to “discover” other BGP neighbors. Neighbors have to be configured manually and BGP uses TCP port 179 for the connection.

    BGP Neighbor Adjacency States - NetworkLessons.com

    networklessons.com/bgp/bgp-neighbor-adjacency-states
    networklessons.com/bgp/bgp-neighbor-adjacency-states
    Was this helpful?
  2. People also ask
    What is the output for a BGP neighbor?
    The following example shows output for the BGP neighbor at 10.108.50.2. This neighbor is an internal BGP (iBGP) peer. This neighbor supports the route refresh and graceful restart capabilities. External BGP neighbor may be up to 2 hops away. Table 46 describes the significant fields shown in the display.

    Cisco IOS IP Routing: BGP Command Reference - BGP Commands: sho…

    cisco.com
    What happens when a neighbor receives a BGP prefix?
    When the neighbor receives the prefix it will examine the community value and take proper action whether it is filtering or modifying other attributes. Any BGP prefix can have more than one tag (BGP community); each tag means something or leads to specific unique action.  (you can attach up to 32 communities to a single route).

    BGP Zero to Hero Part 7, BGP Communities - Cisco Learning Network

    learningnetwork.cisco.com
    How do I know if a BGP neighbor was dynamically created?
    The following is sample output from the show ip bgp neighbors command that verifies that the neighbor 192.168.3.2 is a member of the peer group, group192, and belongs to the subnet range group 192.168.0.0/16, which shows that this BGP neighbor was dynamically created:

    Cisco IOS IP Routing: BGP Command Reference - BGP Commands: sho…

    cisco.com
    What if two BGP routers try to become neighbors?
    Neighbors have to be configured manually and BGP uses TCP port 179 for the connection. In this lesson we’ll take a close look at the different “states” when two BGP routers try to become neighbors. Here they are: Idle:This is the first state where BGP waits for a “start event”.

    BGP Neighbor Adjacency States - NetworkLessons.com

    networklessons.com
    How do BGP neighbors exchange routes?
    BGP neighbors exchange routes via Update messages. As Update and Keepalive messages are received, the Hold Timer is reset. If the Hold Timer expires, an error is detected and BGP moves the neighbor back to the Idle state.

    BGP Neighbor States > BGP Fundamentals | Cisco Press

    ciscopress.com
    How far away can a BGP neighbor be?
    External BGP neighbor may be up to 2 hops away. Table 46 describes the significant fields shown in the display. Fields that are preceded by the asterisk character (*) are displayed only when the counter has a nonzero value. IP address of the BGP neighbor and its autonomous system number. Autonomous system number of the neighbor.

    Cisco IOS IP Routing: BGP Command Reference - BGP Commands: sho…

    cisco.com
    Feedback
  3. NetworkLessons.com
    https://networklessons.com/bgp/bgp-nei…

    BGP Neighbor Adjacency States - NetworkLessons.com

    Just like OSPF or EIGRP, BGP establishes a neighbor adjacency with other BGP routers before they exchange any routing information. Unlike other routing protocols however, BGP does not use broadcast or multicast to “discover” …

  4. NetworkLessons.com
    https://networklessons.com/bgp/troubles…

    Troubleshooting BGP Neighbor Adjacency

    In this lesson we’ll start with troubleshooting BGP neighbor adjacencies. Once the neighbor adjacency is working, you can focus on troubleshooting missing route advertisements. Key to troubleshooting BGP is understanding how BGP forms …

  5. Cisco
    https://www.cisco.com/.../irg_book/irg_bgp5.html

    Cisco IOS IP Routing: BGP Command Reference

  6. Cisco Community
    https://community.cisco.com/t5/switching/bgp...

    Solved: BGP neighbor received routes - Cisco Community

  7. NetworkLessons.com
    https://networklessons.com/bgp/internal-bgp-border...

    Internal BGP (Border Gateway Protocol) explained

  8. Cisco Learning Network
    https://learningnetwork.cisco.com/s/articl…

    BGP Zero to Hero Part 7, BGP Communities - Cisco …

    Feb 7, 2022 · The BGP community attribute is a numerical value tag that can be assigned to a specific prefix and advertised to other neighbors. When the neighbor receives the prefix it will examine the community value and take …

  9. Cisco Press
    https://www.ciscopress.com/articles/article.asp?p=...

    Basic BGP Configuration > BGP Fundamentals - Cisco Press

  10. Cisco
    https://www.cisco.com/.../22166-bgp-tr…

    Troubleshoot Common BGP Issues - Cisco

    Oct 25, 2022 · This document provides flowcharts for several options to troubleshoot BGP issues. If you have the output of a show ip bgp , show ip bgp neighbors , show ip bgp summary , or show tech-support command from your …

  11. Cisco
    https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/...

    IP Routing: BGP Command Reference, Cisco IOS XE Release 3SE …

  13. Some results have been removed