How To Configure OSPF Single Area In 2 Routers

OSPF Single Area VLSM

Given Network: 195.100.0.0

Required hosts on Router 1: 26

Required hosts on Router 2: 14

R1<= 26 hosts

26<= 2ⁿ – 2

26<= 2⁵ – 2

26<= 32 – 2

26<= 30

Total number of network bits= 32

32 – n = 32 – 5 = 27 (CIDR value of Router 1 i.e. Given network)

i.e. 195.100.0.0/27

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 192.100.0.32/?

Now find FVH, LVH and Broadcast address

Given Network	195	100	0	0
First Valid Host-FVH	195	100	0	1
Last Valid Host-LVH	195	100	0	30
Broadcast	195	100	0	31
New Network	195	100	0	32

R2<= 14 hosts

14<= 2ⁿ – 2

14<= 2⁴ – 2

14<= 16 – 2

14<= 14

Total number of network bits = 32

32 – n = 32 -4 = 28 (CIDR value of new network i.e. Router 2)

i.e. 195.100.0.32/28

N.S.M = 11111111. 11111111. 11111111.11110000

                        = 255.255.255.240

Block Size        = 256 – N.S.M

                        = 256 – 240 = 16

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 192.100.0.48/?

Now find FVH, LVH and Broadcast address

Given Network	195	100	0	32
First Valid Host-FVH	195	100	0	1
Last Valid Host-LVH	195	100	0	46
Broadcast	195	100	0	47
New Network	195	100	0	48

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. 195.100.0.48/30

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 3. This network can be used in future.

so the new network is 192.100.0.52 /?

Now find FVH, LVH and Broadcast address

Given Network	195	100	0	48
First Valid Host-FVH	195	100	0	49
Last Valid Host-LVH	195	100	0	50
Broadcast	195	100	0	51
New Network	195	100	0	52

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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 195.100.0.1  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 195.100.0.49 255.255.255.252 R1(config-if)#clock rate 64000 R1(config-if)#no shutdown R1(config-if)#exit R1(config)#exit 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 195.100.0.33 255.255.255.240 R2(config-if)#no shutdown R2(config-if)#exit   R2(config)#interface serial 0/1/0 R2(config-if)#ip address 195.100.0.50 255.255.255.252 R2(config-if)#no shutdown R2(config-if)#exit R2(config)#exit R2#write

OSPF Single Area Configuration on Router 1

R1>enable R1#show ip route connected   C   195.100.0.0/27  is directly connected, FastEthernet0/0   C   195.100.0.48/30  is directly connected, Serial0/0/0   R1#configure terminal R1(config)#router ospf 20 R1(config-router)#network 195.100.0.0        0.0.0.31           area 1 R1(config-router)#network 195.100.0.48      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   195.100.0.32/28  is directly connected, FastEthernet0/0   C   195.100.0.48/30  is directly connected, Serial0/1/0   R2#configure terminal R2(config)#router ospf 20 R2(config-router)#network 195.100.0.32      0.0.0.15           area 1 R2(config-router)#network 195.100.0.48      0.0.0.3             area 1 R2(config-router)#exit R2(config)#exit R2#write

Verification on Router 1

R1#show ip route      195.100.0.0/24 is variably subnetted, 3 subnets, 3 masks C       195.100.0.0/27 is directly connected, FastEthernet0/0 O       195.100.0.32/28 [110/65] via 195.100.0.50, 00:00:01, Serial0/0/0 C       195.100.0.48/30 is directly connected, Serial0/0/0

Verification on Router 2

R2#show ip route      195.100.0.0/24 is variably subnetted, 3 subnets, 3 masks O       195.100.0.0/27 [110/65] via 195.100.0.49, 00:00:28, Serial0/1/0 C       195.100.0.32/28 is directly connected, FastEthernet0/0 C       195.100.0.48/30 is directly connected, Serial0/1/0

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