Conference kali::dewbr

1312.0. "OSPF, RIP and VLSM ??" by GIDDAY::MUNN (Slothy Dogs Rule the Earth) Tue Jun 03 1997 04:37

I need some help configuring OSPF and RIP on the router network shown below.
This network was previously running RIP everywhere using a subnetted A class
address. The backbone contains 3 CISCO 4000 routers with 4 ports each which
either connect to another router or to DECbrouter 90's. A segment of this
network is shown below coming off of router #3.

On the Ethernet LAN, UNIX machines run routed to pick up route information.

Although the network is isolated from the real world, the customer in this
case has decided to change the addressing to match offical addresses that
they own.

The problem is that the address blocks have different subnet masks therefore
RIP V1 is going to spit the dummy in trying to route this and the routers
don't support RIP V2. 

It appears that the answer is to use OSPF on the backbone (as OSPF broadcasts
mask information) and extending down to the Brouters, then redistribute the
routing information into RIP (and visa versa) as it enters the LAN. 

To test this, the addresses shown below were set on the various ports.

R3
S0:144.98.1.1 (255.255.255.252)
 | S1:144.98.1.5 (255.255.255.252)
 |  | S2:144.98.1.9 (255.255.255.252)
 |  |  | S3:100.1.10.1 (255.255.255.0)
 |  |  |  |
 |  |  |  |----------------------------------R2---------------R1
 |  |  BR3
 |  |  S0:144.98.1.10 (255.255.255.252)
 |  |  E0:144.97.46.3 (255.255.255.240)
 |  |
 |  BR2
 |  S0:144.98.1.6 (255.255.255.252)
 |  E0:144.97.126.129 (255.255.255.224)
 |
 BR1
 S0:144.98.1.2 (255.255.255.252)
 E0:144.97.67.18 (255.255.255.240)
                                                                            
                                                                            
Just looking at the network branch from R3 to BR1, BR2 & BR3; I set the
configuration as follows:

Note: For the first part of the test, the routers R2 and R3 were left with A
class addresses and RIP routing (ie their original and working
configuration).

BR1:
interface ethernet 0
ip address 144.97.67.18 255.255.255.240
!
interface serial 0
ip address 144.98.1.2 255.255.255.252
!
router rip
network 144.97.0.0
redistribute ospf 100
!
router ospf 100
network 144.98.1.0 0.0.0.3 area 0.0.0.0
redistribute rip metric 1 subnets
!

BR2:
interface ethernet 0
ip address 144.97.126.130 255.255.255.224
!
interface serial 0
ip address 144.98.1.6 255.255.255.252
!
router rip
network 144.97.0.0
redistribute ospf 100
!
router ospf 100
network 144.98.1.4 0.0.0.3 area 0.0.0.0
redistribute rip metric 1 subnets
!

BR3
interface ethernet 0
ip address 144.97.46.3 255.255.255.240
!
interface serial 0
ip address 144.98.1.10 255.255.255.252
!
router rip
network 144.97.0.0
redistribute ospf 100
!
router ospf 100
network 144.98.1.8 0.0.0.3 area 0.0.0.0
redistribute rip metric 1 subnets
!

R3
interface serial 0
ip address 144.98.1.1 255.255.255.252
!
interface serial 1
ip address 144.98.1.5 255.255.255.252
!
!
interface serial 2
ip address 144.98.1.9 255.255.255.252
!
!
interface serial 3
ip address 100.1.10.1 255.255.255.0
!
router rip
network 100.0.0.0
redistribute ospf 100
!
router ospf 100
network 144.98.1.0 0.0.0.3 area 0.0.0.0
network 144.98.1.4 0.0.0.3 area 0.0.0.0
network 144.98.1.8 0.0.0.3 area 0.0.0.0
network 0.0.0.0 255.255.255.255 area 0.0.0.0
redistribute rip metric 1 subnets
!

Look at the IP routing tables, all of the routes seem to be in place, the
router R3 sees all the RIP routes coming in from R1 and R2 plus the variably
subnetted routes in 144.97. In fact pings from router to router seem to work
fine. But in the RIP domain (ie at the brouter ethernet port or the machine
on the LAN's) the routes coming from OSFP don't seem to be present. For
example, routed on a UNIX machine on the LAN at BR1 will see the 144.97.67.16
network and the 144.98.0.0 network but nothing else. This looks fairly
similer to the effect you get when you use try to use VLSM in RIP.

Therefore the redistributionn into RIP does not seem to be working. I'm sure
I haven't set it up correctly. Can someone point out where my mistake is (or
have I mis-understood what OSPF can do in relation to VLSM's) ?

/Richard