Table of Contents
Advertisement
Configuring BGP
3.
4.
5.
6.
7.
8.
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
Catalyst 3750 Switch Software Configuration Guide
34-48
Prefer the route with the highest local preference. Local preference is part of the routing update and
exchanged among routers in the same AS. The default value of the local preference attribute is 100.
You can set local preference by using the bgp default local-preference router configuration
command or by using a route map.
Prefer the route that was originated by BGP running on the local router.
Prefer the route with the shortest AS path.
Prefer the route with the lowest origin type. An interior route or IGP is lower than a route learned
by EGP, and an EGP-learned route is lower than one of unknown origin or learned in another way.
Prefer the route with the lowest multi -exit discriminator (MED) metric attribute if the neighboring
AS is the same for all routes considered. You can configure the MED by using route maps or by using
the default-metric router configuration command. When an update is sent to an IBGP peer, the
MED is included.
Prefer the external (EBGP) path over the internal (IBGP) path.
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.
Chapter 34
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.
Configuring IP Unicast Routing
78-16180-02
Hide quick links:
Advertisement
Table of Contents
Troubleshooting
