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Chapter 32
Configuring IP Unicast Routing
9.
10.
11.
Beginning in privileged EXEC mode, follow these steps to configure some decision attributes:
Command
Step 1
configure terminal
Step 2
router bgp autonomous-system
Step 3
bgp best-path as-path ignore
Step 4
neighbor {ip-address | peer-group-name} next-hop-self (Optional) Disable next-hop processing on BGP updates
Step 5
neighbor {ip-address | peer-group-name} weight
weight
Step 6
default-metric number
Step 7
bgp bestpath med missing-as-worst
Step 8
bgp always-compare med
Step 9
bgp bestpath med confed
Step 10
bgp deterministic med
78-17058-01
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 destination (the
shortest path to the BGP next-hop).
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.
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 router or the loopback (virtual) address, but
might be implementation-specific.
Purpose
Enter global configuration mode.
Enable a BGP routing process, assign it an AS number,
and enter router configuration mode.
(Optional) Configure the router to ignore AS path length
in selecting a route.
to a neighbor by entering a specific IP address to be used
instead of the next-hop address.
(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.
(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.
(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.
(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.
(Optional) Configure the switch to consider the MED in
choosing a path from among those advertised by different
subautonomous systems within a confederation.
(Optional) Configure the switch to consider the MED
variable when choosing among routes advertised by
different peers in the same AS.
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Configuring BGP
32-47
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