cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
484
Views
0
Helpful
4
Replies

How do we know if Type- 5 AS belongs to Area 0 or Area 1

mahesh18
Level 6
Level 6

Hi all,

I have one question about  knowing which database is for Area 0 and Area 2.

Below is output

3550SMIB#                          sh ip ospf database

            OSPF Router with ID (2.2.2.2) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         3     (DNA) 0x80000005 0x00ADF9 1
2.2.2.2         2.2.2.2         121         0x800003E1 0x007A4F 2
3.3.3.3         3.3.3.3         1303        0x800001BC 0x002641 3
4.4.4.4         4.4.4.4         2022        0x80000189 0x00BAF4 2

                Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
192.168.5.3     4.4.4.4         2022        0x8000017F 0x0039E4
192.168.6.3     4.4.4.4         2022        0x800003AA 0x009F54

                Summary Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
10.10.0.0       3.3.3.3         1303        0x80000019 0x0009FC
10.10.0.1       1.1.1.1         8     (DNA) 0x80000001 0x0070B2
10.10.1.1       1.1.1.1         8     (DNA) 0x80000001 0x0065BC
10.10.2.1       1.1.1.1         8     (DNA) 0x80000001 0x005AC6
10.10.3.1       1.1.1.1         8     (DNA) 0x80000001 0x004FD0
10.20.0.1       2.2.2.2         1897        0x80000018 0x00B547
10.20.1.1       2.2.2.2         1897        0x80000018 0x00AA51
10.20.2.1       2.2.2.2         1897        0x80000018 0x009F5B
10.20.3.1       2.2.2.2         1897        0x80000018 0x009465
10.20.4.0       1.1.1.1         3     (DNA) 0x80000001 0x00587D
192.168.3.2     2.2.2.2         882         0x80000136 0x00FC93
192.168.4.2     1.1.1.1         8     (DNA) 0x80000001 0x007D4C
192.168.4.2     3.3.3.3         1308        0x8000001A 0x000F99

                Summary ASB Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
5.5.5.5         1.1.1.1         3     (DNA) 0x80000001 0x0003DF

                Router Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum Link count
2.2.2.2         2.2.2.2         125         0x80000057 0x00BE05 2
5.5.5.5         5.5.5.5         1946        0x80000059 0x0008E6 6

                Summary Net Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum
0.0.0.0         2.2.2.2         125         0x8000004D 0x00647D

                Type-7 AS External Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum Tag
172.16.1.0      5.5.5.5         945         0x8000004E 0x00A5E3 0

As we see above it shows us Area 0 and Area 2 database.

But below Database  Type - 5 As   does not have any area name -- like Area 0 or 2.************************************************

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
0.0.0.0         4.4.4.4         754         0x8000002D 0x006A0C 1
64.59.135.150   4.4.4.4         754         0x800003AE 0x00F5B2 0
172.16.1.0      5.5.5.5         1195        0x80000017 0x003092 0
172.31.0.0      4.4.4.4         754         0x8000002E 0x008475 0
172.31.1.0      4.4.4.4         754         0x8000002E 0x00797F 0
172.31.2.0      4.4.4.4         754         0x8000002E 0x006E89 0
172.31.3.0      4.4.4.4         754         0x8000002E 0x006393 0

My question is how do we tell  know that Type -5 AS  belongs to which area  ??????????????

Thanks

MAhesh

1 Accepted Solution

Accepted Solutions

Hello Mahesh,

So it means that Route 172.31.0.0 does not belong to any particular area and as per you It is domain-wide right?

Correct.

Best regards,

Peter

View solution in original post

4 Replies 4

Peter Paluch
Cisco Employee
Cisco Employee

Hello Mahesh,

Your question is very valid. The explanation is simple - an LSA5 does not belong to any particular area because it describes an external network, i.e. a network that is outside your OSPF domain, not in any of its areas. Therefore it is not assigned to any particular area. It is domain-wide.

Of course you may be interested in which area is the ASBR located that imports this external route. There is a limited possibility for learning it. You need to have a look at the Advertising Router field in the corresponding LSA5 and search for it between LSA1 (if it is in one of your own areas), or between LSA4 if it is in a different area. However, if a LSA4 describes that ASBR, you cannot tell from your own link state database where the ASBR is located. You would need to go to the router that originated the LSA4 (that would obviously be an ABR) and look into its own database for corresponding LSA1 or LSA4, optionally proceeding even further in the same way.

Feel welcome to ask further.

Best regards,

Peter

Hi Peter,

Thanks for reply.

I login to Router -- ID 4.4.4.4 

I did sh ip ospf database

2691Router#sh ip ospf database

            OSPF Router with ID (4.4.4.4) (Process ID 1)

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
0.0.0.0         4.4.4.4         506         0x8000002F 0x00660E 1
64.59.135.150   4.4.4.4         506         0x800003B0 0x00F1B4 0
172.16.1.0      5.5.5.5         982         0x80000019 0x002C94 0
172.31.0.0      4.4.4.4         506         0x80000030 0x008077 0
172.31.1.0      4.4.4.4         506         0x80000030 0x007581 0
172.31.2.0      4.4.4.4         509         0x80000030 0x006A8B 0
172.31.3.0      4.4.4.4         509         0x80000030 0x005F95 0
2691Router#

Here also it shows Type 5 .

This is what i did on 2691 originating Router --------

I had configured them as static Route

ip route 172.31.0.0 255.255.255.0 Null0

ip route 172.31.1.0 255.255.255.0 Null0

ip route 172.31.2.0 255.255.255.0 Null0

ip route 172.31.3.0 255.255.255.0 Null0

router ospf 1

router-id 4.4.4.4

log-adjacency-changes

redistribute static metric 50 metric-type 1 subnets router ospf 1

So in this example we can say that 172.31.0.0 as it is external route and we redistribute it into OSPF domain and

ASBR router which is 2691 advertise it as Type 5 LSA to other OSPF speaking routers in Area 0 and 1.

So it means that Route 172.31.0.0 does not belong to any particular area and as per you It is domain-wide right?

Thanks

Mahesh

Hello Mahesh,

So it means that Route 172.31.0.0 does not belong to any particular area and as per you It is domain-wide right?

Correct.

Best regards,

Peter

Hi Peter,

Thanks for the reply.

Now my concept is clear.

Regards

MAhesh

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: