{"id":1138,"date":"2020-11-19T02:45:00","date_gmt":"2020-11-19T02:45:00","guid":{"rendered":"http:\/\/bytereign.com\/?p=1138"},"modified":"2025-04-22T10:21:27","modified_gmt":"2025-04-22T09:21:27","slug":"bgp-border-gateway-protocol-quick-reference-notes","status":"publish","type":"post","link":"https:\/\/bytereign.com\/?p=1138","title":{"rendered":"BGP (Border Gateway Protocol): Quick Reference Notes"},"content":{"rendered":"\t\t
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Quick BGP notes, for network professionals seeking insights into key attributes, the path vector protocol, and routing decisions.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Border Gateway Protocol (BGP)<\/span><\/div>
\u00a0<\/div>
Basic Information<\/span><\/div>
  1. Version: BGPv4<\/span><\/li>
  2. Standard: RFC 427<\/span><\/li>
  3. Type: EGP -Path Vector<\/span><\/li>
  4. iBGP Administrative Distance: 200<\/span><\/li>
  5. eBGP Administrative Distance: 20<\/span><\/li>
  6. Transport: Port 179<\/span><\/li>
  7. Authentication: MD5<\/span><\/li><\/ol>
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    Packet Types<\/span><\/div>
    1. Open (BGP Version, Local AS Number, BGP Router ID)<\/span><\/li>
    2. Keepalive (Every 60 Seconds)<\/span><\/li>
    3. Update (Exchange Routes)<\/span><\/li>
    4. Notification (Fatal Errors)<\/span><\/li><\/ol>
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      BGP Table Types<\/span><\/div>
      1. BGP Neighbor Table<\/span><\/li>
      2. BGP Table (also known as BGP topology table)<\/span><\/li>
      3. BGP Routing Table\u00a0<\/span><\/li><\/ol>
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        BGP Session Establishment between peers<\/span><\/div>
        1. TCP \u2013 Syn \u2013 Syn-Ack -Ack (3-way handshake)<\/span><\/li>
        2. Open – Open<\/span><\/li>
        3. Keepalive – Keepalive<\/span><\/li>
        4. Update – Update<\/span><\/li><\/ol>
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          FSM – Finite State Machine<\/span><\/div>
          1. Idle – The opening BGP state.<\/span><\/li>
          2. Connect – BGP waits for a TCP connection with the remote peer. If successful, an OPEN message is sent. If failed, the session is placed in an Active state.<\/span><\/li>
          3. Active – BGP tries to begin a TCP connection with the remote peer. If successful, an OPEN message is sent. If unsuccessful, BGP will wait for a Connect-Retry timer to terminate, and place the session back in a Connect State.<\/span><\/li>
          4. OpenSent – BGP has both built the TCP connection and sent an OPEN Message, and is expecting a reply OPEN Message. Once it gets a reply OPEN Message, the BGP peer will send a KEEPALIVE message.<\/span><\/li>
          5. OpenConfirm – BGP hears for a reply KEEPALIVE message.<\/span><\/li>
          6. Established – BGP peer session is completely built. UPDATE messages including routing data will now be sent.<\/span><\/li><\/ol>
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            Path Selection<\/span><\/div>
            1. Weight (Highest)<\/span><\/li>
            2. Local Preference (Highest)<\/span><\/li>
            3. Self-Originated<\/span><\/li>
            4. AS Path (Shortest)<\/span><\/li>
            5. Origin (IGP over EGP)<\/span><\/li>
            6. MED (Lowest)<\/span><\/li>
            7. External (eBGP over iBGP)<\/span><\/li>
            8. IGP Cost (Lowest)<\/span><\/li>
            9. Multiple paths<\/span><\/li>
            10. eBGP Peering (Oldest)<\/span><\/li>
            11. Router ID (Lowest)<\/span><\/li>
            12. Cluster List (Minimum)<\/span><\/li>
            13. Neighbor address (Lowest)<\/span><\/li><\/ol>
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              BGP Commands of Cisco, Juniper & Alcatel<\/span><\/div>
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              Cisco BGP Commands<\/span><\/div>
              1. show ip bgp<\/span><\/li>
              2. show ip bgp neighbors<\/span><\/li>
              3. show ip bgp neighbors <address> advertised-routes<\/span><\/li>
              4. show ip bgp neighbors <address> received-routes<\/span><\/li>
              5. show ip bgp community<\/span><\/li>
              6. show ip bgp dampened paths<\/span><\/li>
              7. show ip bgp peer-group<\/span><\/li>
              8. show ip bgp regexp<\/span><\/li>
              9. clear ip bgp<\/span><\/li>
              10. clear ip bgp dampening<\/span><\/li>
              11. show ip bgp summary<\/span><\/li><\/ol>
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                Juniper BGP Commands<\/span><\/div>
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                1. show route protocol bgp<\/span><\/li>
                2. show route community<\/span><\/li>
                3. show route damping decayed<\/span><\/li>
                4. show bgp neighbor<\/span><\/li>
                5. show route advertising-protocol bgp <address><\/span><\/li>
                6. show route receive-protocol bgp <address><\/span><\/li>
                7. show bgp group<\/span><\/li>
                8. show route aspath-regex<\/span><\/li>
                9. clear bgp neighbor<\/span><\/li>
                10. clear bgp damping<\/span><\/li>
                11. show bgp summary<\/span><\/li><\/ol>
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                  Alcatel BGP Commands<\/span><\/div>
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                  1. show router route-table protocol bgp<\/span><\/li>
                  2. show router bgp routes community<\/span><\/li>
                  3. show router bgp damping<\/span><\/li>
                  4. show router bgp neighbor<\/span><\/li>
                  5. show router bgp neighbor (x.x.x.x) advertised-routes<\/span><\/li>
                  6. show router bgp neighbor (x.x.x.x) received-routes<\/span><\/li>
                  7. show router bgp group<\/span><\/li>
                  8. show router bgp routes (family) aspath-regex<\/span><\/li>
                  9. clear router bgp neighbor<\/span><\/li>
                  10. clear router bgp damping<\/span><\/li>
                  11. show router bgp summary<\/span><\/li><\/ol>
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                    Other important BGP topics<\/span><\/div>
                    \u00a0<\/div>
                    1. BGP Split horizon<\/span><\/li>
                    2. BGP Synchronization<\/span><\/li>
                    3. BGP Route-Reflectors, Confederations<\/span><\/li>
                    4. BGP Communities<\/span><\/li>
                    5. BGP Summarization<\/span><\/li>
                    6. BGP Route Dampening<\/span><\/li>
                    7. BGP Backdoor<\/span><\/li><\/ol>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"

                      Quick BGP notes, for network professionals seeking insights into key attributes, the path vector protocol, and routing decisions. Border Gateway Protocol (BGP)\u00a0Basic<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_eb_attr":"","footnotes":""},"categories":[1,49],"tags":[],"class_list":["post-1138","post","type-post","status-publish","format-standard","hentry","category-blog","category-network-engineering"],"_links":{"self":[{"href":"https:\/\/bytereign.com\/index.php?rest_route=\/wp\/v2\/posts\/1138","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bytereign.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bytereign.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bytereign.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bytereign.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1138"}],"version-history":[{"count":43,"href":"https:\/\/bytereign.com\/index.php?rest_route=\/wp\/v2\/posts\/1138\/revisions"}],"predecessor-version":[{"id":1804,"href":"https:\/\/bytereign.com\/index.php?rest_route=\/wp\/v2\/posts\/1138\/revisions\/1804"}],"wp:attachment":[{"href":"https:\/\/bytereign.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1138"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bytereign.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1138"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bytereign.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1138"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}