From: Tim Fletcher (tim@fletchmail.net)
Date: Sun Jul 06 2003 - 00:33:16 GMT-3
At 12:41 PM 7/4/03 -0500, Brian McGahan wrote:
>Jim,
>
> This TAC document is wrong. The purpose of running OSPF demand
>circuit is to maintain an accurate view of the routing topology, while
>minimizing the amount of time that your DDR link is up solely due to
>routing protocol traffic.
>
> By denying OSPF as interesting traffic, adjacency cannot be
>maintained over the DDR link unless it is up for some other reason.
>When the link goes down due to no interesting traffic passing over the
>link within the idle timeout, OSPF adjacency will be lost as soon as the
>dead interval expires.
And once the adjacency is broken you will have no routes across the link. Without any routes across the link, you will not have any interesting traffic. Without any interesting traffic the link will never come up.
> When running OSPF demand circuit, OSPF *should* be specified as
>interesting traffic.
>
>HTH,
>
>Brian McGahan, CCIE #8593
>Director of Design and Implementation
>brian@cyscoexpert.com
>
>CyscoExpert Corporation
>Internetwork Consulting & Training
>Toll Free: 866.CyscoXP
>Fax: 847.674.2625
>
>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>Of
>> ccie2be
>> Sent: Friday, July 04, 2003 5:22 AM
>> To: Group Study
>> Subject: OSPF Demand Circuit
>>
>> Hi,
>>
>> After checking the archieves, I didn't find anything that specifically
>> addressed this question, so here goes.
>>
>> I thought that when a BRI interface is configured as an ip ospf
>> demand-circuit, it will automatically suppress ospf hello's as long as
>the
>> interface is configured as a p2p or p2m ospf network type.
>>
>> However, in the example at
>> http://www.cisco.com/warp/public/129/config-bri-map.html , it shows an
>> access
>> list being used to prevent ospf hello's in addition to the ip ospf
>> demand-circuit command being configured.
>>
>> Is it really necessary (or just sometimes necessary) to use an access
>list
>> to
>> deny ospf hello's (packets addressed to 224.0.0.5) when one side of
>the
>> isdn
>> circuit is configured as an ip ospf demand circuit? If so, why is
>that?
>> Also, if the access-list in addtion to the ip ospf demand circuit is
>only
>> needed in certain situations, what are those situations?
>>
>> Thanks, Jim
>>
>>
>>
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