notes: BGP Next Hop Processing

- When a packet is passed between iBGP peers, NO next-hop processing is done, unless confederations are used.
- When a packet is passed between eBGP peers, the next-hop field is modified to the IP address of the sending eBGP router.
- If the receiving BGP router is in the same subnet as the current next-hop address,
the next-hop field remains unchanged to optimize packet forwarding. Typically seen on multiaccess networks.
- Careful with next-hop processing on NBMA networks. The next-hop must be reachable. Rather use a sub-interface interface on different subnet or alternatively disable next-hop processing.

- Next-hop processing could be changed in one of two ways:
> As mentioned above with the 'neighbor next-hop-self' command.
> or with a route-map by setting the 'ip next-hop'.
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COMMANDS
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1.  using route-map - Changes the next-hop to the IP specified
- Applies the route-map to the iBGP peer to change next-hop processing

route-map SET-NEXT-HOP

set ip next-hop {ip}
!

router bgp {asn}

neighbor {ip|peer-group} route-map {name} {in|out}

2.  next hop self- Changes next-hop processing at edge router to the local peering address
- Instructs iBGP to use this router as the next-hop for routes advertised


neighbor {ip|peer-group} next-hop-self