From: Yasmin Lara (ylara@sunsetlearning.com)
Date: Tue Jan 09 2007 - 00:17:02 ART
What's the difference between assigning an administrative distance of 200 for
a specific route and using the backdoor feature?
For example:
router bgp 300
distance 200 192.168.100.1 0.0.0.0 99
!
access-list 99 permit 44.4.4.0 0.0.0.255
vs.
router bgp 300
network 44.4.4.0 mask 255.255.255.0 backdoor?
According to the documentation: "A backdoor network is assigned an
administrative distance of 200. The objective is to make Interior Gateway
Protocol (IGP) learned routes preferred. A backdoor network is treated as a
local network, except that it is not advertised. A network that is marked as a
back door is not sourced by the local router, but should be learned from
external neighbors. The BGP best path selection algorithm does not change when
a network is configured as a back door." "Changing the default
administrative distances is not recommended because changing the
administrative distance may lead to routing loops."
I don't understand why changing the distance may lead to routing loops and I
don't understand what difference is makes to set the distance for the route as
200 with the distance command or with the backdoor command. Am I missing
something?
Thx!!!
Yasmin.
This archive was generated by hypermail 2.1.4 : Thu Feb 08 2007 - 23:46:56 ART