Concept Guide

Network Next Hop Metric LocPrf Weight Path
*> 7.0.0.0/29 10.114.8.33 0 0 18508 ?
*> 7.0.0.0/30 10.114.8.33 0 0 18508 ?
*> 9.2.0.0/16 10.114.8.33 10 0 18508 701 i
AS Path
The AS path is the list of all ASs that all the prexes 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
DellEMC#show ip bgp paths
Total 30655 Paths
Refcount Metric Path
3 18508 701 3549 19421 i
3 18508 701 7018 14990 i
3 18508 209 4637 1221 9249 9249 i
2 18508 701 17302 i
26 18508 209 22291 i
75 18508 209 3356 2529 i
2 18508 209 1239 19265 i
1 18508 701 2914 4713 17935 i
162 18508 209 i
2 18508 701 19878 ?
31 18508 209 18756 i
2 18508 209 7018 15227 i
10 18508 209 3356 13845 i
3 18508 209 701 6347 7781 i
1 18508 701 3561 9116 21350 i
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 trac 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 ap 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
MBGP is an extensison of BGP to carry routing information for multiple network-layer protocols such as IPv4 unicast and multicast, and
IPv6 unicast. MBGP provides support for multiple network layer protocol address families that allows to dene independent policy and
peering congurations. MBGP carries dierent set of routes depending on the protocol. It carries routing information for IPv4 multicast and
IPv6 unicast routes. Multiprotocol extensions for BGP (MBGP) is dened in IETF RFC 2858. MBGP allows dierent types of address
families to be distributed in parallel.
Border Gateway Protocol (BGP)
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