Figure 20. BGP Best Path Selection
Best Path Selection Details
1.
Prefer the path with the largest WEIGHT attribute.
2.
Prefer the path with the largest LOCAL_PREF attribute.
3.
Prefer the path that was locally
Originated via a network
command,
redistribute
command or
aggregate-address
command.
a.
Routes originated with the
Originated via a network
or
redistribute
commands are
preferred over routes originated with the
aggregate-address
command.
4.
Prefer the path with the shortest AS_PATH (unless the
bgp bestpath as-path ignore
command
is configured, then AS_PATH is not considered). The following criteria apply:
a.
An AS_SET has a path length of 1, no matter how many ASs are in the set.
b.
A path with no AS_PATH configured has a path length of 0.
c.
AS_CONFED_SET is not included in the AS_PATH length.
d.
AS_CONFED_SEQUENCE has a path length of 1, no matter how many ASs are in the
AS_CONFED_SEQUENCE.
5.
Prefer the path with the lowest ORIGIN type (IGP is lower than EGP, and EGP is lower than
INCOMPLETE).
6.
Prefer the path with the lowest multi-exit discriminator (MED) attribute. The following criteria apply:
a.
This comparison is only done if the first (neighboring) AS is the same in the two paths; the MEDs
are compared only if the first AS in the AS_SEQUENCE is the same for both paths.
b.
If you entered the
bgp always-compare-med
command, MEDs are compared for all paths.
172
Border Gateway Protocol IPv4 (BGPv4)
Summary of Contents for Z9000
Page 1: ...Dell Configuration Guide for the Z9000 System 9 7 0 0 ...
Page 80: ...grub reboot 80 Management ...
Page 128: ... 0 Te 1 1 Te 1 2 rx Flow N A N A 128 Access Control Lists ACLs ...
Page 491: ...Figure 70 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 491 ...
Page 496: ...Figure 73 MSDP Default Peer Scenario 1 496 Multicast Source Discovery Protocol MSDP ...
Page 497: ...Figure 74 MSDP Default Peer Scenario 2 Multicast Source Discovery Protocol MSDP 497 ...
Page 498: ...Figure 75 MSDP Default Peer Scenario 3 498 Multicast Source Discovery Protocol MSDP ...
Page 760: ...Figure 100 Single and Double Tag TPID Match 760 Service Provider Bridging ...
Page 761: ...Figure 101 Single and Double Tag First byte TPID Match Service Provider Bridging 761 ...