From: Ken.Farrington@barclayscapital.com
Date: Tue Sep 23 2003 - 05:24:51 GMT-3
Just one thing,
When I make R2 and R3 just a normal area 3 (no stub) I get the routes from
R3 back via R2 and into area 0 on R1
on R3
11.0.0.0/24 is subnetted, 4 subnets
C 11.0.3.0 is directly connected, Loopback14
C 11.0.2.0 is directly connected, Loopback13
C 11.0.1.0 is directly connected, Loopback12
C 11.0.0.0 is directly connected, Loopback11
on R2
11.0.0.0/24 is subnetted, 4 subnets
O E1 11.0.3.0 [110/21] via 30.96.100.18, 00:02:29, FastEthernet0/0
O E1 11.0.2.0 [110/21] via 30.96.100.18, 00:02:29, FastEthernet0/0
O E1 11.0.1.0 [110/21] via 30.96.100.18, 00:02:29, FastEthernet0/0
O E1 11.0.0.0 [110/21] via 30.96.100.18, 00:02:29, FastEthernet0/0
on R1
11.0.0.0/24 is subnetted, 4 subnets
O E1 11.0.3.0 [110/85] via 30.96.100.2, 00:03:12, Serial0/0
O E1 11.0.2.0 [110/85] via 30.96.100.2, 00:03:12, Serial0/0
O E1 11.0.1.0 [110/85] via 30.96.100.2, 00:03:12, Serial0/0
O E1 11.0.0.0 [110/85] via 30.96.100.2, 00:03:12, Serial0/0
----------------------------------------------------------------------------
-----------------------------
But when I make router R2 and R3 into an NSSA, I dont receive the routes on
the "backbone only" router R1
On R3
11.0.0.0/24 is subnetted, 4 subnets
C 11.0.3.0 is directly connected, Loopback14
C 11.0.2.0 is directly connected, Loopback13
C 11.0.1.0 is directly connected, Loopback12
C 11.0.0.0 is directly connected, Loopback11
On R2
11.0.0.0/24 is subnetted, 4 subnets
O N1 11.0.3.0 [110/21] via 30.96.100.18, 00:00:49, FastEthernet0/0
O N1 11.0.2.0 [110/21] via 30.96.100.18, 00:00:49, FastEthernet0/0
O N1 11.0.1.0 [110/21] via 30.96.100.18, 00:00:49, FastEthernet0/0
O N1 11.0.0.0 [110/21] via 30.96.100.18, 00:00:49, FastEthernet0/0
on R1
**No routes for 11.0.0.0 **
Would anyone know why this is?
Many thx once again.
-----Original Message-----
From: Ken.Farrington@barclayscapital.com
[mailto:Ken.Farrington@barclayscapital.com]
Sent: 23 September 2003 08:41
To: ccielab@groupstudy.com
Subject: RE: OSPF - ABR/ASBR in NSSAs
Brilliant - Thx very much indeed :)
-----Original Message-----
From: Snow, Tim [mailto:timothy.snow@eds.com]
Sent: 23 September 2003 08:37
To: 'Ken.Farrington@barclayscapital.com'
Cc: 'ccielab@groupstudy.com'
Subject: RE: OSPF - ABR/ASBR in NSSAs
If Area3 is a stub, no external information (type 5) will be allowed to be
present in the area so your first statement is correct. A NSSA would allow
you to bend the rules of a typically stub and allow external information in
as type 7's. Those will be converted from type 7 to type 5 at R2.
The reason that r2 becomes an ASBR is because it's converting the type 7 LSA
originally from r3 into a type 5. Due to the fact that it's originating the
type 5, it needs to create a type 4 (Type 4: ASBR-summary-LSA) to advertise
itself to the rest of the network. Normally an ABR will generate a type-4
for an ASBR in it's area so the rest of the network knows how to get to the
type 5's but since this is an NSSA, the r2 in your example, needs to
advertise itself.
In your 3rd statement, if you were to insert another router in between r2
and r3 then yes, it will be a "normal internal area router". It will flood
those type 7's to the ABR. Keep in mind that stub area flags need to match
on it just like all other router.
Hope that helps.
Tim
#12042
-----Original Message-----
From: Ken.Farrington@barclayscapital.com
[mailto:Ken.Farrington@barclayscapital.com]
Sent: Tuesday, September 23, 2003 3:18 AM
To: ccielab@groupstudy.com
Subject: OSPF - ABR/ASBR in NSSAs
Please expand e-mail window to see diagram correctly :)
AREA0 Area3
+----+ +----+ +----+ 3
| R1 |--------------------| R2 |---------------------| R3 | nets Redist
connected subnets
+----+ 10.0.0.0/24 +----+ 11.0.0.0/24 +----+
ABR
ASBR
11.0.1.0/24
11.0.2.0/24
11.0.3.0/24
Guys,
I have the above setup, and if I keep area 3 as a normal area, R3 is an
ASBR (redist con) and R2 is an ABR. If I make area 3 a stub area I have to
use an NSSA correct, as a stub area does not expect Type 5s.
Please could you confirm this?
Also, If I have area 3 as an NSSA, why does R2 become an ASBR as well as an
ABR? Is it to do
with the fact R2 has to convert a type7 LSA to a type5 LSA and this function
automatically makes R2 into an ASBR?
If so far is correct? if I inserted a router between R2 and R3 (called
R2a), would this just be a
normal internal area router? as it would pass L7s (I assume) to R2 or would
it become something else?
Please could someone confirm this concept.
Many thx indeed,
Ken
________________________________________________________________
Ken Farrington
Global Networks, Barclays Capital, 5 The North Colonnade, Canary
Wharf, London, E14 4BB
* Tel : 020 7773 3550
* Mob : 07768-866655
* ken.farrington@barcap.com
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