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CCNA 4.6: Configure and verify single-homed branch connectivity using eBGP IPv4

Overview:
External Border Gateway Protocol (eBGP) is when BGP is run between two different Autonomous Systems

 

Study Notes:

  • BGP is a path vector protocol
  • It makes routing decisions based on the Best Path Algorithm
  • BGP exchanges routing information with a neighbor (peer) router
  • BGP uses Autonomous Systems.  BGP routers in other ASs are typically under the control of another company.  For example, your company has a BGP router that peers with the ISPs BGP router.  Your BGP router will be in a different AS than the ISP router. Those routers participate in eBGP.
  • If you had two BGP routers in your AS than they would talk to each other via iBGP.
  • BGP uses TCP port 179
  • BGP assigns the first valid path as the current best path
  • BGP then compares the best path with the next path in the list, until it reaches the end of the list of valid paths
  • There are 15 rules determining the best path.  You don’t need to know these for the CCNA. Just understand that it goes through a process from 1 to 15 to figure out the best path.

 

Labs:

PacketTracer Lab: CCNA-4.6-Configure-and-verify-single-homed-branch-connectivity-using-eBGP-IPv4.pkt

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Links:

https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html


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