DGS-3610 Series Configuration Guide Chapter 29 BGP Configuration
29.9.6 Other Related Configuration
By default, if two paths with full identical path attributes are received from different EBGP
Peers during the selection of the optimal path, we will select the optimal path according to
the path received sequence. You can select the path with smaller Router ID as the optimal
path by configuring the following commands.
Router(config-router)# bgp bestpath
compare-routerid
(Optional) Allow the BGP to compare with the router ID
when the optimal path is selected.
29.10 Selection of Optimal Path for BGP
The selection of the optimal route is an important part of the BGP protocol. The following will
describe the selection process of the BGP route protocol in details:
1. If the route table item is invalid, it will not participate in the selection of the optimal route.
The invalid table item includes the items the next hop can not be reached
and the vibrated table items.
2. Select the route with the maximal weight.
3. If else, select the route with high LOCAL_PREF attribute value.
4. If else, select the route generated by this BGP speaker.
The route generated by this BGP speaker includes that generated by the network
command, the redistribute command and the aggregate command.
5. If else, select the route with the shortest AS length.
6. If else, select the route with the lowest ORIGIN attribute value.
7. If else, select the route with the smallest MED value.
8. If else, the priority of the EBGP path is higher than that of the route of the IBGP path
and the AS confederation, and the priority for the IBGP path and the AS confederation is
identical.
9. If else, select the routing with the smallest IGP metric to reach the next hop.
10. If else, select the route which advertises that the router ID of the BGP speaker for this
route is small.
Above is the optical process of the route by default configuration. You can
change the selection process of the route by the CLI command. For
instance, you can use the bgp bestpath as-path ignore command to
make the step 5 in the optimal process of the route invalid.
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