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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter32 Configuring IP Unicast Routing Configuring BGP
9. Prefer the route that can be reached through the closest IGP neighbor (the lowest IGP metric). This
means that the router will prefer the shortest internal path within the AS to reach the d estination (t he
shortest path to the BGP next-hop).
10. If the following conditions are all true, insert the route for this path into the IP routing table:
•Both the best route and this route are external.
•Both the best route and this route are from the same neighboring autonomous system.
•maximum-paths is enabled.
11. If multipath is not enabled, prefer the route with the lowest IP address value for the BGP router ID.
The router ID is usually the highest IP address on the rout er or the lo opba ck ( virtu al ) ad dre ss, but
might be implementation-specific.
Beginning in privileged EXEC mode, follow these steps to configure some decision a ttributes:
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 router bgp autonomous-system Enable a BGP routing process, assign it an AS number,
and enter router configuration mode.
Step3 bgp best-path as-path ignore (Optional) Configure the router to ignore AS path length
in selecting a route.
Step4 neighbor {ip-address | peer-group-name} next-hop-self (Optional) Disable next-hop processing on BGP updates
to a neighbor by entering a specific IP address to be used
instead of the next-hop address.
Step5 neighbor {ip-address | peer-group-name} weight
weight (Optional) Assign a weight to a neighbor connection.
Acceptable values are from 0 to 65535; the largest weight
is the preferred route. Routes learned through another
BGP peer have a default weight of 0; routes sourced by the
local router have a default weight of 32768.
Step6 default-metric number (Optional) Set a MED metric to set preferred paths to
external neighbors. All routes without a MED will also be
set to this value. The range is 1 to 4294967295. The lowest
value is the most desirable.
Step7 bgp bestpath med missing-as-worst (Optional) Configure the switch to consider a missing
MED as having a value of infinity, making the path
without a MED value the least desirable path.
Step8 bgp always-compare med (Optional) Configure the switch to compare MEDs for
paths from neighbors in different autonomous systems. By
default, MED comparison is only done among paths in the
same AS.
Step9 bgp bestpath med confed (Optional) Configure the switch to consider the MED in
choosing a path from among those advertised by different
subautonomous systems within a confederation.
Step10 bgp deterministic med (Optional) Configure the switch to consider the MED
variable when choosing among routes advertised by
different peers in the same AS.