From: Narbik Kocharians (narbikk@gmail.com)
Date: Tue Jan 09 2007 - 01:12:20 ART
The way I look at this is that one uses a macro and the second way you do it
manually. If you remember the same thing can be done in Spanning-tree, root
primary versus the priority command.
Remember when entering either one of the commands in BGP, always think of
the traffic leaving the router and the return traffic.
On 1/8/07, Yasmin Lara <ylara@sunsetlearning.com> wrote:
>
> 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.
>
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-- Narbik Kocharians CCIE# 12410 (R&S, SP, Security) CCSI# 30832 Network Learning, Inc. (CCIE class Instructor) www.ccbootcamp.com (CCIE Training)
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