At 06:33 PM 9/12/00, Luobin Yang wrote:
>Dear Priscilla,
>
>Thanks for your reply. I do have a copy of Routing TCP/IP. I am not sure,
>but I think by using the command "area 2 nssa no-redistribution" , we can
>turn off the P-bit.
But wouldn't that cause other routers in area 2 to lose their route to
172.16.30.0? The case studies in the OSPF chapter talk more about this
issue. Unfortunately, they don't use quite the same topology as you are
using, but perhaps you can translate what they say to your topology.
>But my question is that why in a totally stubby area, there exists
>situations that External routes could be flooded into? Totally stubby area
>should block type 3, type 4 and type 5 LSAS.
I can't say why. I think you would have to talk to the OSPF protocol
designers. They must have thought there was some good reason for it or they
wouldn't have invented the P-bit. Where are Howard and Pamela when we need
them? Actually, I know that Howard is at the RIPE and European Operators
Forum....
Priscilla
>Luobin Yang
>
>>From: Priscilla Oppenheimer <[EMAIL PROTECTED]>
>>To: luobin Yang <[EMAIL PROTECTED]>,[EMAIL PROTECTED]
>>Subject: Re: Why External type 5 LSA is distributed to a totally stubby
>>area ?
>>Date: Tue, 12 Sep 2000 16:18:57 -0700
>>
>>Do you have a copy of Doyle's Routing TCP/IP book by any chance? If yes,
>>check out the discussion on page 483 and Figure 9.42. The Figure looks just
>>like what you are describing. The discussion says:
>>
>>"The NSSA External LSA has a flag in its header known as the P-bit. The
>>NSSA ASBR has the option of setting or clearing the P-bit. If the NSSA's
>>ABR receives a type 7 LSA with the P-bit set to one, it will translate the
>>type 7 LSA into a type 5 LSA and flood it throughout the other areas. If
>>the P-bit is set to zero, no translation will take place and the
>>destination in the type 7 LSA will not be advertised outside of the NSSA."
>>
>>Sounds like your P-bit is set! That can be a dangerous thing if you are not
>>so stubby. &;-) Seriously, hopefully this is a start for figuring out
>>what's going on. I'm going to try to find out if there's any configuration
>>parameters related to this P-bit and get back to you if I find anything, or
>>maybe somebody else knows.
>>
>>Priscilla
>>
>>At 03:55 PM 9/12/00, luobin Yang wrote:
>>>Dear group,
>>>
>>>I have such a scenerio:
>>>
>>>RouterB is connected to RouterA using Serial 0, RouterC is connected to
>>>RouterA using Serial 1. Interface E0 of Router A is configured as Area
>>>0, Serial0(to RouterC) of RouterA is configured as Area 2 (nssa area) ,
>>>Serial1(to RouterB) of RouterA is configured as Area 1 (totally stubby
>>>area ).
>>>
>>>On routerC, I configured OSPF and EIGRP, Serial 1(to RouterA) is running
>>>OSPF and belongs to area 2 which is a NSSA. E0 is running EIGRP. If I
>>>redistribute network of E0 ( for example 172.16.30.0 ) from EIGRP to
>>>OSPF, I found 172.16.30.0 is redistributed to Area 1 which is a totally
>>>stubby area.
>>>
>>>Does anybody know the reason why?
>>>
>>>Thanks a lot!
>>>Luobin
>>>
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>>
>>
>>________________________
>>
>>Priscilla Oppenheimer
>>http://www.priscilla.com
>
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