As Path; Next Hop; Multiprotocol Bgp - Dell S4048–ON Configuration Manual

AS Path

The AS path is the list of all ASs that all the prefixes listed in the update have passed through.
The local AS number is added by the BGP speaker when advertising to a eBGP neighbor.
NOTE: Any update that contains the AS path number 0 is valid.
The AS path is shown in the following example. The origin attribute is shown following the AS path information (shown in bold).
Example of Viewing AS Paths
Dell#show ip bgp paths
Total 30655 Paths
Address Hash Refcount Metric Path
0x4014154 0 3
0x4013914 0 3
0x5166d6c 0 3
0x5e62df4 0 2
0x3a1814c 0 26
0x567ea9c 0 75
0x6cc1294 0 2
0x6cc18d4 0 1
0x5982e44 0 162
0x67d4a14 0 2
0x559972c 0 31
0x59cd3b4 0 2
0x7128114 0 10
0x536a914 0 3
0x2ffe884 0 1

Next Hop

The next hop is the IP address used to reach the advertising router.
For EBGP neighbors, the next-hop address is the IP address of the connection between the neighbors. For IBGP, the EBGP next-hop
address is carried into the local AS. A next hop attribute is set when a BGP speaker advertises itself to another BGP speaker outside its
local AS and when advertising routes within an AS. The next hop attribute also serves as a way to direct traffic to another BGP speaker,
rather than waiting for a speaker to advertise. When a next-hop BGP neighbor is unreachable, then the connection to that BGP neighbor
goes down after hold down timer expiry. The connection flap can also be obtained immediately with Fallover enabled. BGP routes that
contain the next-hop as the neighbor address are not sent to the neighbor. You can enable this feature using the neighbor sender-
side-loopdetect command.
NOTE: For EBGP neighbors, the next-hop address corresponding to a BGP route is not resolved if the next-hop address is not
the same as the neighbor IP address.
NOTE: The connection between a router and its next-hop BGP neighbor terminates immediately only if the router has received
routes from the BGP neighbor in the past.

Multiprotocol BGP

Multiprotocol extensions for BGP (MBGP) is defined in IETF RFC 2858. MBGP allows different types of address families to be distributed in
parallel.
MBGP allows information about the topology of the IP multicast-capable routers to be exchanged separately from the topology of normal
IPv4 and IPv6 unicast routers. It allows a multicast routing topology different from the unicast routing topology.
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Border Gateway Protocol IPv4 (BGPv4) 185