You may have cases where you will be running another routing protocol in your network together with OSPF. Or maybe your company is using OSPF and it has lately bought another company which has RIP routing protocol running on it, and those 2 networks need to be merged together. For this, you require to redistribute one routing protocol into the other so both networks can be merged.
Remember, the router that has peer with an OSPF router and is connected to another network is called ASBR. So logically, the route redistribution (in Huawei is called route import) should happen on the ASBR router.
To make things clearer for you, I would like to run a LAB to show you how this can happen. Let’s go to the LAB directly.
I have this scenario. Each router has a loopback interface acting as a connected network as following:
[mepr-show rules=”319″ unauth=”message”]
OSPF is already configured on all routers and on the 2 different areas as per the graph. I decided to not show you in this LAB how to configure OSPF because you should by now already know how to configure OSPF in multi area. I will be focusing on configure RIP routing protocol between R3 and R5, then to show you how the route import can happen so R5 will know about all routes in OSPF, and all routers in OSPF know about the routes in RIP.
1st let me check whether R1 can ping from his loopback interface to all other routers’ loopback interfaces then I know that OSPF is working well.
R1 is able to reach all loopback interfaces, so OSPF is well configured on all routers.
Let’s start configuring RIP on R3.
Here I have enabled RIP on R3 and advertised the network 192.168.35.0. Let’s enable RIP on R5 now.
Here I have enabled RIP on R5 and advertised the connected networks. Now R3 should learn from RIP about the loopback interface of R5 which is 22.214.171.124/24. Let’s check this on R3 routing table.
Indeed!!! R3 can see the network 126.96.36.199/24 from RIP, as well as he can see other loopbacks from OSPF. That’s why R3 is called an ASBR.
But what about R1, R2 and R4, do they know about the network 188.8.131.52/24? Let’s check that.
R1 does not see the network 184.108.40.206/24 in his routing table.
Let us check R2 now.
Also, R2 doesn’t have an entry in his routing table for 220.127.116.11/24.
Let us check R4.
Same result on R4.
The reason why R1, R2 and R4 do not know about 18.104.22.168/24 is because this network is advertised in RIP while R1, R2 and R4 run OSPF, so 2 different routing protocols.
To allow the OSPF routers to know about the network 22.214.171.124/24, then we should import (redistribute) RIP routes into OSPF then the OSPF routers will see RIP routes as OSPF routes. You got me?
This is only done on the ASBR router which is R3. Let me directly show you how this can be done.
As easy as that, 1 command inside the OSPF process will import the rip routes to OSPF.
Let’s check if R1 see now 126.96.36.199/24 in his routing table.
Look at that ???? – R1 see now the network 188.8.131.52/24 and it has learned it from OSPF, you can see it has O_ASE, that means that this is OSPF external router which is LSA type 5 if you remember from the last chapter.
Excellent. Let’s try to ping from R1 to 184.108.40.206 and see if it can reach it.
Not yet!!!! And the reason why is because R5, which is running RIP, does not know how to send the ping back to R1 because he does not know any OSPF network. For this to work, we need to import routes from OSPF to RIP this time, and again this should be done on the ASBR router. Let me show you how this can be done.
I have imported all OSPF routes into RIP. Let’s check if R5 can see the routes that was imported from OSPF to RIP.
WoW!!!!! R5 can see all loopback interfaces of the OSPF routers, and he sees them as RIP, because we have imported the OSPF routes to RIP.
By doing that, I should be able now from R1 to ping 220.127.116.11 successfully because R5 knows how to send the ping back. Let’s try.
Indeed, the ping is working now. Excellent!!! That’s what I wanted to show you in this LAB. I will keep the LAB operation because I want to still show you something else in this chapter.