Administrator Guide

Example of Viewing AS Paths
Dell#show ip bgp paths
Total 30655 Paths
Address Hash Refcount Metric
Path
0x4014154 0 3 18508 701 3549 19421 i
0x4013914 0 3 18508 701 7018 14990 i
0x5166d6c 0 3 18508 209 4637 1221 9249 9249 i
0x5e62df4 0 2 18508 701 17302 i
0x3a1814c 0 26 18508 209 22291 i
0x567ea9c 0 75 18508 209 3356 2529 i
0x6cc1294 0 2 18508 209 1239 19265 i
0x6cc18d4 0 1 18508 701 2914 4713 17935 i
0x5982e44 0 162 18508 209 i
0x67d4a14 0 2 18508 701 19878 ?
0x559972c 0 31 18508 209 18756 i
0x59cd3b4 0 2 18508 209 7018 15227 i
0x7128114 0 10 18508 209 3356 13845 i
0x536a914 0 3 18508 209 701 6347 7781 i
0x2ffe884 0 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. It can also be set 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.
Dell Networking OS allows you to set the Next Hop attribute in the CLI. Setting the Next Hop attribute lets you determine a router as the
next hop for a BGP neighbor.
Multiprotocol BGP
Multiprotocol extensions for BGP (MBGP) are dened in IETF RFC 2858. MBGP allows dierent 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 dierent from the unicast routing topology.
NOTE
: It is possible to congure BGP peers that exchange both unicast and multicast network layer reachability information
(NLRI), but you cannot connect multiprotocol BGP with BGP. Therefore, you cannot redistribute multiprotocol BGP routes into
BGP.
Implement BGP with Dell Networking OS
The following sections describe how to implement BGP on Dell Networking OS.
Additional Path (Add-Path) Support
The Add-path feature reduces convergence times by advertising multiple paths to its peers for the same address prex without replacing
existing paths with new ones. By default, a BGP speaker advertises only the best path to its peers for a given address prex. If the best
path becomes unavailable, the BGP speaker withdraws its path from its local RIB and recalculates a new best path. This requires both IGP
and BGP convergence and can therefore be a lengthy process.
BGP add-path on Dell Networking OS reduces the time taken for BGP convergence by advertising multiple paths to its peers for the same
address prex without new paths implicitly replacing the existing paths. An iBGP speaker that receives multiple paths from its peers should
Border Gateway Protocol IPv4 (BGPv4)
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