Tune Bgp Best-Path Calculation - Cisco NCS 5500 Series Configuration Manual

Implementing BGP
Example:
RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 2002
Creates a neighbor and assigns a remote autonomous system number to it.
Step 5 address-family { ipv4 | ipv6 } unicast
Example:
RP/0/RP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast
Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.
To see a list of all the possible keywords and arguments for this command, use the CLI help (?).
Step 6
weight weight-value
Example:
RP/0/RP0/CPU0:router(config-bgp-nbr-af)# weight 41150
Assigns a weight to all routes learned through the neighbor.
Step 7
commit
What to Do Next
You the clear bgp command for the newly configured weight to take effect.

Tune BGP Best-Path Calculation

BGP routers typically receive multiple paths to the same destination. The BGP best-path algorithm determines
the best path to install in the IP routing table and to use for forwarding traffic. The BGP best-path comprises
of three steps:
• Step 1—Compare two paths to determine which is better.
• Step 2—Iterate over all paths and determines which order to compare the paths to select the overall best
• Step 3—Determine whether the old and new best paths differ enough so that the new best path should
The order of comparison determined by Step 2 is important because the comparison operation is not
Note
transitive; that is, if three paths, A, B, and C exist, such that when A and B are compared, A is better, and
when B and C are compared, B is better, it is not necessarily the case that when A and C are compared,
A is better. This nontransitivity arises because the multi exit discriminator (MED) is compared only among
paths from the same neighboring autonomous system (AS) and not among all paths.
Algorithm, on page 130
Perform this task to change the default BGP best-path calculation behavior.
path.
be used.
provides additional conceptual details.
BGP Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
Tune BGP Best-Path Calculation
BGP Best Path
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