Users 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 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.
MBGP uses either an IPv4 address configured on the interface (which is used to establish the IPv6 session) or a stable IPv4 address that
is available in the box as the next-hop address. As a result, while advertising an IPv6 network, exchange of IPv4 routes does not lead to
martian next-hop message logs.
NOTE:
It is possible to configure 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 prefix without replacing
existing paths with new ones. By default, a BGP speaker advertises only the best path to its peers for a given address prefix. If the best
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Border Gateway Protocol IPv4 (BGPv4)