RE: OSPF --- subnet mask of IA routes

From: Bashir Sulaiman (bashir.sulaiman@netwise.co.uk)
Date: Mon Nov 04 2002 - 10:30:38 GMT-3


Benny,

Without the 'ip ospf network point-to-point' statement on the loopback
interfaces, OSPF treats loopback interface as a stub network and therefore
you will see the address as x.x.x.x/32 (host route). Hence the:
----------------------------------------------------------------------------
----------------------------------
R1 routing table:
     172.16.0.0/32 is subnetted, 2 subnets
O IA 172.16.1.1 [110/11] via 150.50.7.6, 01:03:20, Ethernet0
O IA 172.16.2.1 [110/11] via 150.50.7.6, 01:03:20, Ethernet0
----------------------------------------------------------------------------
-----------------------------------

So, you should configure:

Inter lo0
Ip adder x.x.x.x 255.255.255.0
'ip ospf network point-to-point'
inter lo1
Ip adder y.y.y.y 255.255.255.0
'ip ospf network point-to-point'

  Hope this helps

Bashir

 -----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Benny Chong
Sent: 02 November 2002 02:54
To: ccielab@groupstudy.com
Subject: OSPF --- subnet mask of IA routes

Hi,

R1 and R2 in area 0, R2 has 2 loopback interface with ip address
172.16.1.1/24 and 172.16.2.1/24. I don't understand when R1 learned about
this two loopback interfaces, it doesn't learn the network 172.16.1.0/24 and

172.16.2.0/24, but it learns 172.16.1.1 and 172.16.2.1 instead? I use
'network 172.16.1.0 0.0.0.255 area 4' and 'network 172.16.2.0 0.0.0.255 area

4) on R2.

R1----------R2 (lo1 and lo2 area 4)
     area 0

The question require that R1 learns these two subnets with a /24 mask, and
the solution require configure 'ip ospf network point-to-point' under the
two loopback interfaces in R2. Can someone kindly explain to me? Thanks a
lot!

Benny
**********************************************************************
'show ip ospf database' in R1:
                Summary Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
172.16.1.1 200.0.0.6 665 0x80000003 0xC1EA
172.16.2.1 200.0.0.6 665 0x80000003 0xB6F4

R2 routing table:
     172.16.0.0/24 is subnetted, 2 subnets
C 172.16.1.0 is directly connected, Loopback1
C 172.16.2.0 is directly connected, Loopback2

R1 routing table:
     172.16.0.0/32 is subnetted, 2 subnets
O IA 172.16.1.1 [110/11] via 150.50.7.6, 01:03:20, Ethernet0
O IA 172.16.2.1 [110/11] via 150.50.7.6, 01:03:20, Ethernet0



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