Weight; Local Preference - Dell Force10 Z9000 Configuration Manual

11. Prefer the external path originated from the BGP router with the lowest router ID. If both paths are
external, prefer the oldest path (first received path). For paths containing a Route Reflector (RR)
attribute, the originator ID is substituted for the router ID.
12. If two paths have the same router ID, prefer the path with the lowest cluster ID length. Paths without a
cluster ID length are set to a 0 cluster ID length.
13. Prefer the path originated from the neighbor with the lowest address. (The neighbor address is used in
the BGP neighbor configuration, and corresponds to the remote peer used in the TCP connection with
the local router.)
After a number of best paths is determined, this selection criteria is applied to group's best to determine the
ultimate best path.
In non-deterministic mode (the
the order in which they arrive. This method can lead to FTOS choosing different best paths from a set of
paths, depending on the order in which they were received from the neighbors since MED may or may not
get compared between adjacent paths. In deterministic mode, FTOS compares MED between adjacent
paths within an AS group since all paths in the AS group are from the same AS.

Weight

The Weight attribute is local to the router and is not advertised to neighboring routers. If the router learns
about more than one route to the same destination, the route with the highest weight will be preferred. The
route with the highest weight is installed in the IP routing table.

Local Preference

Local Preference (LOCAL_PREF) represents the degree of preference within the entire AS. The higher the
number, the greater the preference for the route.
The Local Preference (LOCAL_PREF) is one of the criteria used to determine the best path, so keep in
mind that other criteria may impact selection, as shown in
LOCAL_PREF is the only attribute applied. In
Although the path through the Router A is shorter (one hop instead of two) the LOCAL_PREF settings
have the preferred path go through Router B and AS300. This is advertised to all routers within AS100
causing all BGP speakers to prefer the path through Router B.
| Border Gateway Protocol
168
bgp non-deterministic-med
Figure 8-5, AS100 has two possible paths to AS 200.
command is applied), paths are compared in
Figure 8-4. For this example, assume that