In this lab, I am gonna teach you How to configure OSPF single area in 3 routers
Table of Contents
OSPF Single Area Configuration VLSM
Given Network: 192.80.10.0
1) Required hosts on Router 1= 28
2) Required hosts on Router 2= 20
3) Required hosts on Router 3= 6
R1<= 28
28<= 2n – 2
28<= 25 – 2
28<= 32 – 2
28<= 30
Total number of network bits = 32
32 – n = 32 – 5 = 27 (CIDR value of given network i.e. Router 1)
i.e. 192.80.10.0/27
N.S.M = 11111111. 11111111. 11111111.11100000
= 255.255.255.224
Block Size = 256 – N.S.M
= 256 – 224 = 32
Note: Add this block size in given network so that we can get our new network for Router 2.
So the new network is 192.80.10.32/?
Now find FVH, LVH and Broadcast address
| Given Network | 192 | 80 | 10 | 0 |
| First Valid Host-FVH | 192 | 80 | 10 | 1 |
| Last Valid Host-LVH | 192 | 80 | 10 | 30 |
| Broadcast | 192 | 80 | 10 | 31 |
| New Network | 192 | 80 | 10 | 32 |
R2<= 20
20<= 2n – 2
20<= 25 – 2
20<= 32 – 2
20<= 30
Total number of network bits = 32
32 – n = 32 – 5 = 27 (CIDR value of given network i.e. Router 2)
i.e. 192.80.10.32/27
N.S.M = 11111111. 11111111. 11111111.11100000
= 255.255.255.224
Block Size = 256 – N.S.M
= 256 – 224 = 32
Note: Add this block size in given network so that we can get our new network for Router 3.
So the new network is 192.80.10.64/?
Now find FVH, LVH and Broadcast address
| Given Network | 192 | 80 | 10 | 32 |
| First Valid Host-FVH | 192 | 80 | 10 | 33 |
| Last Valid Host-LVH | 192 | 80 | 10 | 62 |
| Broadcast | 192 | 80 | 10 | 63 |
| New Network | 192 | 80 | 10 | 64 |
R3<= 6
6<= 2n – 2
6<= 23 – 2
6<= 8 – 2
6<= 6
Total number of network bits = 32
32 – n = 32 – 3 = 29 (CIDR value of given network i.e. Router 3)
i.e. 192.80.10.64/29
N.S.M = 11111111. 11111111. 11111111.11111000
= 255.255.255.248
Block Size = 256 – N.S.M
= 256 – 248 = 8
Note: Add this block size in given network so that we can get our new network for Router 1 and 2 (Virtual Network).
So the new network is 192.80.10.72/?
Now find FVH, LVH and Broadcast address
| Given Network | 192 | 80 | 10 | 64 |
| First Valid Host-FVH | 192 | 80 | 10 | 65 |
| Last Valid Host-LVH | 192 | 80 | 10 | 70 |
| Broadcast | 192 | 80 | 10 | 71 |
| New Network | 192 | 80 | 10 | 72 |
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Router 1 & 2 <= 2 hosts (we required only two IP to connect 2 routers)
2 <= 2n – 2
2 <= 22 – 2
2 <= 4 – 2
2 <= 2
Total number of network bits = 32
32 – n = 32 – 2 = 30 (CIDR of Virtual network (R1&R2)
i.e. 198.10.10.72/30
N.S.M = 11111111.11111111.11111111.11111100
= 255.255.255.252
Block Size = 256 – N.S.M
= 256 – 252 = 4
Note: Add this block size in given network so that we can get our new network for Router 2 and 3 (Virtual Network).
so the new network is 192.80.10.76/?
Now find FVH, LVH and Broadcast address
| Given Network | 192 | 80 | 10 | 72 |
| First Valid Host-FVH | 192 | 80 | 10 | 73 |
| Last Valid Host-LVH | 192 | 80 | 10 | 74 |
| Broadcast | 192 | 80 | 10 | 75 |
| New Network | 192 | 80 | 10 | 76 |
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Router 2 & 3 <= 2 hosts (we required only two IP to connect 2 routers)
2 <= 2n – 2
2 <= 22 – 2
2 <= 4 – 2
2 <= 2
Total number of network bits = 32
32 – n = 32 – 2 = 30 (CIDR of Virtual network (R2&R3)
i.e. 198.10.10.76/30
N.S.M = 11111111.11111111.11111111.11111100
= 255.255.255.252
Block Size = 256 – N.S.M
= 256 – 252 = 4
Note: Add this block size in given network so that we can get our new network for Router 4. This network can be used in future.
so the new network is 192.80.10.80/?
Now find FVH, LVH and Broadcast address
| Given Network | 192 | 80 | 10 | 76 |
| First Valid Host-FVH | 192 | 80 | 10 | 77 |
| Last Valid Host-LVH | 192 | 80 | 10 | 78 |
| Broadcast | 192 | 80 | 10 | 79 |
| New Network | 192 | 80 | 10 | 80 |
Basic Configuration on Router 1
| Router>enable Router#configure terminal Router(config)#hostname R1 R1(config)#interface fastEthernet 0/0 R1(config-if)#ip address 192.80.10.1 255.255.255.224 R1(config-if)#no shutdown R1(config-if)#exit R1(config)#interface serial 0/0/0 R1(config-if)#ip address 192.80.10.73 255.255.255.252 R1(config-if)#clock rate 64000 R1(config-if)#no shutdown R1#write |
Basic Configuration on Router 2
| Router>enable Router#configure terminal Router(config)#hostname R2 R2(config)#interface fastEthernet 0/0 R2(config-if)#ip address 192.80.10.33 255.255.255.224 R2(config-if)#no shutdown R2(config-if)#exit R2(config)#interface serial 0/1/0 R2(config-if)#ip address 192.80.10.74 255.255.255.252 R2(config-if)#no shutdown R2(config-if)#exit R2(config)#interface serial 0/0/0 R2(config-if)#ip address 192.80.10.77 255.255.255.252 R2(config-if)#clock rate 64000 R2(config-if)#no shutdown R2(config-if)#exit R2(config)#exit R2#write |
Basic Configuration on Router 3
| Router>enable Router#configure terminal Router(config)#hostname R3 R3(config)#interface fastEthernet 0/0 R3(config-if)#ip address 192.80.10.65 255.255.255.248 R3(config-if)#no shutdown R3(config-if)#exit R3(config)#interface serial 0/1/0 R3(config-if)#ip address 192.80.10.78 255.255.255.252 R3(config-if)#no shutdown R3(config-if)#exit R3(config)#exit R3#write |
OSPF Single Area Configuration on Router 1
| R1>enable R1#show ip route connected C 192.80.10.0/27 is directly connected, FastEthernet0/0 C 192.80.10.72/30 is directly connected, Serial0/0/0 R1#configure terminal R1(config)#router ospf 20 R1(config-router)#network 192.80.10.0 0.0.0.31 area 1 R1(config-router)#network 192.80.10.72 0.0.0.3 area 1 R1(config-router)#exit R1(config)#exit R1#write |
OSPF Single Area Configuration on Router 2
| R2>enable R2#show ip route connected C 192.80.10.32/27 is directly connected, FastEthernet0/0 C 192.80.10.72/30 is directly connected, Serial0/1/0 C 192.80.10.76/30 is directly connected, Serial0/0/0 R2#configure terminal R2(config)#router ospf 20 R2(config-router)#network 192.80.10.32 0.0.0.31 area 1 R2(config-router)#network 192.80.10.72 0.0.0.3 area 1 R2(config-router)#network 192.80.10.76 0.0.0.3 area 1 R2(config-router)#exit R2(config)#exit R2#write |
OSPF Single Area Configuration on Router 3
| R3>enable R3#show ip route connected C 192.80.10.64/29 is directly connected, FastEthernet0/0 C 192.80.10.76/30 is directly connected, Serial0/1/0 R3#configure terminal R3(config)#router ospf 20 R3(config-router)#network 192.80.10.64 0.0.0.7 area 1 R3(config-router)#network 192.80.10.76 0.0.0.3 area 1 R3(config-router)#exit R3(config)#exit R3#write |
Verification on Router 1
| R1#show ip route 192.80.10.0/24 is variably subnetted, 5 subnets, 3 masks C 192.80.10.0/27 is directly connected, FastEthernet0/0 O 192.80.10.32/27 [110/65] via 192.80.10.74, 00:01:12, Serial0/0/0 O 192.80.10.64/29 [110/129] via 192.80.10.74, 00:00:25, Serial0/0/0 C 192.80.10.72/30 is directly connected, Serial0/0/0 O 192.80.10.76/30 [110/128] via 192.80.10.74, 00:01:12, Serial0/0/0 |
Verification on Router 2
| R2#show ip route 192.80.10.0/24 is variably subnetted, 5 subnets, 3 masks O 192.80.10.0/27 [110/65] via 192.80.10.73, 00:01:31, Serial0/1/0 C 192.80.10.32/27 is directly connected, FastEthernet0/0 O 192.80.10.64/29 [110/65] via 192.80.10.78, 00:00:54, Serial0/0/0 C 192.80.10.72/30 is directly connected, Serial0/1/0 C 192.80.10.76/30 is directly connected, Serial0/0/0 |
Verification on Router 3
| R3#show ip route 192.80.10.0/24 is variably subnetted, 5 subnets, 3 masks O 192.80.10.0/27 [110/129] via 192.80.10.77, 00:01:19, Serial0/1/0 O 192.80.10.32/27 [110/65] via 192.80.10.77, 00:01:19, Serial0/1/0 C 192.80.10.64/29 is directly connected, FastEthernet0/0 O 192.80.10.72/30 [110/128] via 192.80.10.77, 00:01:19, Serial0/1/0 C 192.80.10.76/30 is directly connected, Serial0/1/0 |
