Austin's SWE Notes 😭

    Ebgp (External Border Gateway Protocol)

    Handle external BGP (Border Gateway protocol) routing between different AS (Autonomous System)

    Two eBGP (External border gateway protocol) router combined is called a eBGP route

    The next hop attribute of eBGP will be updated to its corresponding eBGP route.

    The list of AS Path of eBGP is prepends to its current list to create a path.

    Example

    For example in this diagram

    Pasted image 20240713221121.png

    R1 and R2 are eBGP (External border gateway protocol) peering since they belongs to 2 different AS (Autonomous System).

    In this case, if I do show ip bgp sum it might look like this

    Router# show ip bgp summary
BGP router identifier 203.0.113.1, local AS number 64512
BGP table version is 15, main routing table version 15
10 network entries using 1200 bytes of memory
12 path entries using 768 bytes of memory
6/6 BGP path/bestpath attribute entries using 672 bytes of memory
3 BGP AS-PATH entries using 72 bytes of memory
1 BGP community entries using 24 bytes of memory
0 BGP extended community entries using 0 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 2736 total bytes of memory
BGP activity 10/0 prefixes, 12/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down State/PfxRcd
192.0.2.2       4 65000     120     115       15    0    0 01:23:45       10
198.51.100.2    4 65001      90      85       15    0    0 00:45:30        5

    The ASN of our neighbour is different.

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