Saturday, December 28, 2013

OSPF Core Configuration

CCNP Lab Documentation:
In this below network scenario there are five manageable routers named R1, R2, R3, R4, R5 where different types of configuration has been done and one switch also connected but there is  nothing configuration has been done in switch. In the below Scenario R1 router works as a ASBR (Autonomous System Border Router) because it is connected with the others routes where OSPF protocol has not been configured. R2 & R3 Router works as a ABR (Area Border Router) because these routers are border router for Area 0 to Area 10 and Area 0 to Area 20. Following configuration has been done in below Router
On router 1.
1. Host name has been changed in R1. R1(config)#R1(config)#hostname R1R1(config)#hostname R1
2. Ip address 172.30.0.1 /24 has been assign on interface fa 0/0.
R1(config)#interface FastEthernet0/0
R1(config)#ip address 172.30.0.1 255.255.255.0
R1(config)#no shutdown
3. Static routing has been done for Null0
R1(config)# ip route 172.16.0.0 255.255.255.0 Null0
R1(config)# ip route 172.16.1.0 255.255.255.0 Null0
R1(config)# ip route 172.16.2.0 255.255.255.0 Null0
R1(config)# ip route 172.16.3.0 255.255.255.0 Null0
On Router 2.
1. Host name has been changed in R2 using same command used by R1 Router.
2. Ip address 172.30.0.2 / 24 has been assign for int fa 0/0
3. Ip address 172.30.10.2 / 24 has been assign for int se 0/0
4. Bandwidth has been fixed at 500kbps using this command R2(config-if)#bandwidth 500
On Router 3.
1. Host name has been changed in R3 using same command used by R1 Router.
2. Ip address 172.30.0.3 / 24 has been assign for int fa 0/0
3. Ip add ress  172.30.20.3 /24 has been assign for int se 0/0
4. Bandwidth has been fixed at 500kbps using same command used by R2 router
On Router 4.
1. Host name has been changed in R4 router using same command used by R1 Router
2. Four Loopback ip address has been assign in Router 4 using below command
R4(config)#interface loopback1
 R4(config)#ip address 10.20.0.1 255.255.255.0
R4(config)#interface loopback2
 R4(config)#ip address 10.20.1.1 255.255.255.0
R4(config)#interface loopback3
 R4(config)#ip address 10.20.3.1 255.255.255.0
R4(config)#interface loopback4
 R4(config)#ip address 10.20.4.1 255.255.255.0
3. Ip address 172.30.20.4 / 24 has been assign for int se 0/0 with 500 kbps bandwidth.
On Router 5.
1. Host name has been changed in R5 router using same command used by R1 Router
2. Four Loopback ip address has been assign in Router 5 using same command used by R4 router.
(Here R5 router used 10.10.0.0 / 24 to 10.10.3.0 network for loopback interface)
3. Ip address 172.30.20.4 / 24 has been assign for int se 0/0 with 500 kbps bandwidth.

Objective:-
1. Configure OSPF for the above network diagram. R1 will act as an ASBR by redistributing a series of static routes into the OSPF network. These routes should NOT increment their metric as they pass through the network and should have an initial OSPF cost of 200. All routers should have a router-id reflecting their hostname; you should be able to ping this router-id throughout the entire OSPF network.

Explanation of Objective:
#config t
#router ospf 1 (Configuring OSPF)
#router id 1.1.1.1 (Assigning Hard Code Router ID) if we don’t assign hard code router ID manually highest loopback ip address will be the router ID, if there is no loopback IP address Highest physical Ip address will be the Router ID.
#network 172.30.0.1 0.0.0.0 area 0 (Assigning specific interface ip address for OSPF)
#network 1.1.1.1 0.0.0.0 area 0 (using this command Router broadcast Router ID 1.1.1.1 to the OSPF network
#default metric 200 (this command is used to stop the increment their metric)

Let’s make an loopback interface for each router to able to ping this routed Id throughout the entire OSPF network.
#config t
#int loopback 1
#ip address 1.1.1.1 255.255.255.255

Note: use the area 0 for ABR router and use their own area Number in remaining router to advertise the router ID on ospf network

2. after completing the initial step of the lab, one of the routers in Area 0 will become the DR and one will become the BDR for the Ethernet segment. Which router will become the DR and BDR? Write DR and BDR next to the respective router below.
o R1
o R2
o R3

Answer: Router 3 become the DR and Router 2 become the BDR after the completing the initial step of the lab.

Let’s make DR and BDR next to the respective router R1, R2, R3 using the following command.

R1#config t
#int fa 0/0
#ip ospf priority 255

R2#conf t
#int fa 0/0
#ip ospf priority 254

By default interface priority value has been set 1, Highest priority value will be the DR router. O priority value doesn’t go in to the DR / BDR election process.


3. Ensure R1 becomes the DR on the Ethernet segment in Area 0. R2 and R3 should not become a DR or BDR for the Ethernet segment in Area 0. After this change is made, what type of neighbor relationship should exist between R1 and R2? What about R2 and R3?

Let’s make R1 as a DR router let’s make R2 and R3 router not a DR / BDR router using following command.

R2#conf t
#int fa 0/0
#ip ospf priority 0

R3#conf t
#int fa 0/0
#ip ospf priority 0

Now in the above network scenario R1 will become the DR router because its priority vale has 255 and R2 and R3 doesn’t go in to the DR / BDR election process because its priority value has been set 0.

Answer after change is made the Relationship between R1 and R2 exist  Full / DR and the relationship between R2 and R3 exist 2way / DOTHER.






4. Implement summarization at the ABRs in the network to make the routing tables throughout the network as efficient as possible.

Let’s summarize the ABR router to make the routing tables throughout the network as efficient as possible.
To summarize the routing tables use the below command.
R2#conf t
#router ospf 1
#area 10 range 10.10.0.0 255.255.252.0

R3#conf t
#router ospf 1
#area 20 range 10.20.0.0 255.255.252.0

Summarization Special (Super netting)
Let’s be clear about the concept of summarization:
Summarization is the process where different networks are merged on a single network. Let’s be clear about the concept of summarization practically.
In the above network scenario we have different loopback interface on R4 like (10.20.0.0 / 24, 10.20.1.0 / 24, 10.20.2.0 / 24, 10.20.3.0 / 24. If we don’t summarize the above network, router will creates four routing table. If we do summarization it is sufficient to cover the above network from one routing table.
Let’s do summarization.
10.20.0.0
10.20.1.0
10.20.2.0
10.20.3.0
 
 







We need to summarize the network in the range of 10.20.0.0 to 10.20.3.0. Here up to 16 bits that means 10.20 are similar. So we are going to summarize 0 to 3 by adopting following method.
0 – 0 0 0 0 0 0 0 0
3 – 0 0 0 0 0 0 1 1
      0 0 0 0 0 0 0 0 (And bit)
Here we have 6 bits value are similar that means its subnet mask is 252.
So, if we do summarize the network 10.20.0.0 to 10.20.3.0 we can put 10.20.0.0 255.255.252.0 value on our area range.
 
 






 5. Implement summarization at the ASBR. The summary route should have the same attributes as the original, individual routes redistributed into the network.

Nothing different to summarize on ABR router and ASBR router conceptually but its command is totally different from each other. To summarize on ASBR router use the following command.
R1#config t
#router ospf 1
#summary-address 172.16.0.0 255.255.252.0

6. The organization plans to upgrade to Gigabit Ethernet in the coming months. OSPF should accurately calculate its metric assuming Gigabit Ethernet will be the fastest link in the network.

This is too much tricky question. Here in the above network scenario fast Ethernet has been used which can carry the data up to 100Mbps. So its metric is 1 which comes from 100 / Mbps. If we set the auto-cost reference bandwidth 1000 its metric will be 10. After one month later organization will upgrade gigabit Ethernet at that time its metric will be 1 which comes from 1000 / Mbps.

To change the reference bandwidth use the following command
R1#conf t
#ruter ospf 1
#auto-cost reference bandwidth 1000
Configure in all router using above mention same command.




 

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