Administrator Guide
they were received from the neighbors because MED may or may not get compared between the adjacent paths. In deterministic
mode, the system compares MED between the adjacent paths within an AS group because all paths in the AS group are from the
same AS.
NOTE: In the Dell Networking OS version 8.3.11.4, the bgp bestpath as-path multipath-relax command is
disabled by default, preventing BGP from load-balancing a learned route across two or more eBGP peers. To enable load-
balancing across dierent eBGP peers, enable the
bgp bestpath as-path multipath-relax command. A system
error results if you congure the
bgp bestpath as-path ignore command and the bgp bestpath as-path
multipath-relax command at the same time. Only enable one command at a time.
The following illustration shows that the decisions BGP goes through to select the best path. The list following the illustration details
the path selection criteria.
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 congured, 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 congured 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).
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Border Gateway Protocol IPv4 (BGPv4)