From: chrlewis@cisco.com
Date: Wed Sep 14 2005 - 23:15:41 GMT-3
Stefan,
There are two causes I believe that are somewhat common for external
routes not being installed. The first is because the forwarding address
as seen in the "show ip ospf database external A.B.C.D" command, where
A.B.C.D is the external route injected, is not known via an intra or
inter area route. The second is te ABR is not generating a type 4
summary LSA. The most common casue of that is if what you think is the
ABR is disconnected from area 0 for some reason.
I have the follwing setup
R2---R3---R5 which maps to you topology below:
The active interfaces on each are as follows:
Router2(config)#do sho ip int brie
Interface IP-Address
Serial2/0 172.16.32.2
Loopback0 192.168.2.2
R3(config-router)#do sho ip int brie
Interface IP-Address
Serial3/0 172.16.32.3
Serial4/0 172.16.35.1
Loopback0 192.168.3.3
Router5(config-router)#do sho ip int brie
Interface IP-Address
Serial3/0 172.16.35.2
Loopback0 192.168.5.5
The relevant OSPF configs are as follows:
R2
router ospf 1
log-adjacency-changes
area 23 nssa
redistribute connected subnets
network 172.16.32.2 0.0.0.0 area 23
R3
router ospf 1
log-adjacency-changes
area 23 nssa
network 172.16.32.3 0.0.0.0 area 23
network 172.16.35.1 0.0.0.0 area 0
R5
router ospf 1
log-adjacency-changes
network 172.16.35.2 0.0.0.0 area 0
The routing tables for R3 and R5 are as follows:
R3
C 172.16.32.0/24 is directly connected, Serial3/0
C 172.16.35.0/30 is directly connected, Serial4/0
O N2 192.168.2.0/24 [110/20] via 172.16.32.2, 00:12:04, Serial3/0
C 192.168.3.0/24 is directly connected, Loopback0
R5
O IA 172.16.32.0/24 [110/128] via 172.16.35.1, 00:12:54, Serial3/0
C 172.16.35.0/30 is directly connected, Serial3/0
C 192.168.5.0/24 is directly connected, Loopback0
O E2 192.168.2.0/24 [110/20] via 172.16.35.1, 00:12:23, Serial3/0
This works as you expect, so Ithink there must be a configuration issue.
I was not able to determine which nssa commands were put on which
router, but I would suggest reducing the configuration to the minimal
one I've shown here, then adding the extra options back in and seeing
which one breaks the operation, then looking at the show ip ospf data
external on each router to figure out why. This is what you should see
R2 injecting the route
Router2#show ip ospf data nssa-external
OSPF Router with ID (192.168.2.2) (Process ID 1)
Type-7 AS External Link States (Area 23)
LS age: 1041
Options: (No TOS-capability, Type 7/5 translation, DC)
LS Type: AS External Link
Link State ID: 192.168.2.0 (External Network Number )
Advertising Router: 192.168.2.2
LS Seq Number: 80000001
Checksum: 0x4F8F
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 172.16.32.2
External Route Tag: 0
Note the Forward Address value
R3
sho ip ospf data external
OSPF Router with ID (192.168.3.3) (Process ID 1)
Type-5 AS External Link States
LS age: 929
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 192.168.2.0 (External Network Number )
Advertising Router: 192.168.3.3
LS Seq Number: 80000001
Checksum: 0xD610
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 172.16.32.2
External Route Tag: 0
Again note the forward address, you will see the same on my R5. The
question to ask is do my routers have an inter or intra area route to
this forward address, if not why not?
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Stefan Grey
Sent: Wednesday, September 14, 2005 10:37 AM
To: ccielab@groupstudy.com
Subject: OSPF LSA7 promplem
Hello group,
I have the following config:
SW1 - R1 - R2
Between sw1 and R1 is Area 1. Between R1, R2 is Area 0.
Area 1 is a (area 1 nssa no-summary network on R1 is configured area 1
nssa no-redistribution nssa and on SW area 1 nssa).
on SW1 we redistribute connected lo to the ospf protocol. This route is
seen on R1 router as N2 route. (As I know and as it should be it should
be LSA7 route). Next this route should be changed to lsa5 and sent next
to R2 but I don't see this route on R2).
What could it be.
I am pretty shure that it is not an issue of the configuration
Thanks to everybody.
This archive was generated by hypermail 2.1.4 : Sun Oct 02 2005 - 14:40:15 GMT-3