From: Jonathan ZD (Nuvo25@hotmail.com)
Date: Wed Mar 16 2005 - 13:40:27 GMT-3
Dear Tom,
Does this mean that eventhough there's non-ABR router with higher router-id,
in the area, the actual ABR of NSSA will be the one and only that will
translate type-7 to type-5 into backbone? (if you confuse about my question,
please scroll down to read the original question for this topic.)
Thanks,
Jonathan.
----- Original Message -----
From: "Tom Lijnse" <Tom.Lijnse@globalknowledge.nl>
To: "Pankaj Madhukar Kulkarni" <PankajKu@hclcomnet.co.in>; "alsontra"
<alsontra@gmail.com>; "Jonathan ZD" <Nuvo25@hotmail.com>; "CCIE - GS"
<ccielab@groupstudy.com>
Sent: Wednesday, March 16, 2005 2:09 AM
Subject: RE: ABR of Not-So-Stubby Area
Hi,
Sorry for the somewhat overdue reply, but I didn't have access to a lab
to get some show command output from until now.
Each router knows the Area Border Routers in its area because the ABRs
advertise their ABR status via their Type-1 Router LSA's.
Let's have a look at the following output:
This is taken from a border router between area 1 and area 0:
R6#sh ip ospf border-routers | i Area 1
i 192.168.4.4 [10] via 172.16.46.4, Ethernet0, ABR, Area 1, SPF 3
So it knows that router 192.168.4.4 is a border router as well.
Let's verify this via the Type-1 LSA:
R6#sh ip ospf database router 192.168.4.4 | b Area 1
Router Link States (Area 1)
Routing Bit Set on this LSA
LS age: 1990
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 192.168.4.4
Advertising Router: 192.168.4.4
LS Seq Number: 80000002
Checksum: 0x1B4A
Length: 36
Area Border Router
...
And as you can see here it has an entry saying that it's an ABR.
So this is how OSPF border routers know the other border routers in
their area.
Hope this helps,
Tom Lijnse
CCIE #11031
Global Knowledge
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Pankaj Madhukar Kulkarni
Sent: donderdag 10 maart 2005 5:45
To: alsontra; Jonathan ZD; CCIE - GS
Subject: RE: ABR of Not-So-Stubby Area
Al,
This is quite interesting...
How does an ABR know about the presence of the other ABR in the area?
Let's continue hunting...
Pankaj
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
alsontra
Sent: Thursday, March 10, 2005 9:24 AM
To: 'Jonathan ZD'; 'CCIE - GS'
Subject: RE: ABR of Not-So-Stubby Area
Search the archives, I had to learn this the hard way....
And the answer is: If you have two ABR to an NSSA, the ABR with the
highest
router-id will translate N2---to--->E2. If for some reason the ABR with
highest RID is not connected to area 0, no conversion will take place.
Easies solution is to change RIDs.
To paraphrase:
NSSA RFC 1587 states that before an NSSA ABR converts Type-7 to Type-5,
all
NSSA ABR must examine all other NSSA ABR to determine the highest
router-id.
The NSSA ABR with the highest router-id "must" the conversion from N2 to
E2.
(Troubleshooting IP protocols, Cisco Press -Page 444)
Happy hunting
Al
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jonathan ZD
Sent: Wednesday, March 09, 2005 9:31 AM
To: CCIE - GS
Subject: ABR of Not-So-Stubby Area
I've followed the link (911networks.com) some one posted it under group
study
one time, I've come across many summary they posted and felt so unsure
about
it. There's one topic that I'd like to ask Group to confirm it.
Under the following link (about Not-So-Stubby Area):
http://911networks.com/node/234?PHPSESSID=38ceea92a6df4ad93d2fba9ecc6477
80
It said that "ONLY THE ROUTER WITH HIGHEST ROUTER-ID DOES THE CONVERSION
LSA
7
TO 5, MAKE SHURE THAT IT'S THE ABR".
Is this true?
Thanks,
Jonathan.
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