Learn to configure DHCP Server on Router and also learn how to setup ip helper address on Router.

How to configure a Router to work as a DHCP Server.

How to setup ip helper address on a Router

How to configure a Router to work as a DHCP Server for indirectly connected networks.

Note: In This Lab we are going To configure Router R1 as DHCP server.

Step 1: Build The Network topology for DHCP Server Lab

Let Me separate R1 R2 and R3 Images separately so that you can see the images clearly.

Step 2: Assign IP Address On Each Router Interfaces.

here I assume you guys know how to assign ip address on router interfaces.

If you have any problem you can see my articles on it.

Step 3: Configure Routing on each Router. router R1,R2 and R3

 Static Routing Configuration On Router R1:

Router(config)#host R1

R1(config)#ip route 4.0.0.0 255.0.0.0 2.0.0.2

R1(config)#ip route 5.0.0.0 255.0.0.0 2.0.0.2

R1(config)#ip route 3.0.0.0 255.0.0.0 2.0.0.2

 Static Routing Configuration On Router R2:

Router(config)#host R2

R2(config)#ip route 1.0.0.0 255.0.0.0 2.0.0.1

R2(config)#ip route 4.0.0.0 255.0.0.0 3.0.0.2

 Static Routing Configuration On Router R3:

Router(config)#host R3

R3(config)#ip route 1.0.0.0 255.0.0.0 3.0.0.1

R3(config)#ip route 2.0.0.0 255.0.0.0 3.0.0.1

R3(config)#ip route 5.0.0.0 255.0.0.0 3.0.0.1

 verify routing Table on Router R1:

R1#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is not set

C 1.0.0.0/8 is directly connected, FastEthernet0/0

C 2.0.0.0/8 is directly connected, Serial0/0/0

S 3.0.0.0/8 [1/0] via 2.0.0.2

S 4.0.0.0/8 [1/0] via 2.0.0.2

S 5.0.0.0/8 [1/0] via 2.0.0.2

 verify routing Table on Router R2:

R2#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is not set

S 1.0.0.0/8 [1/0] via 2.0.0.1

C 2.0.0.0/8 is directly connected, Serial0/0/0

C 3.0.0.0/8 is directly connected, Serial0/0/1

S 4.0.0.0/8 [1/0] via 3.0.0.2

C 5.0.0.0/8 is directly connected, FastEthernet0/0

 verify routing Table on Router R3:

R3#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is not set

S 1.0.0.0/8 [1/0] via 3.0.0.1

S 2.0.0.0/8 [1/0] via 3.0.0.1

C 3.0.0.0/8 is directly connected, Serial0/0/0

C 4.0.0.0/8 is directly connected, FastEthernet0/0

S 5.0.0.0/8 [1/0] via 3.0.0.1

Step 4:Configure DHCP POOL for Each Network on Router R1.

 DHCP POOL creation for network 1.0.0.0 and POOL CCNA.

R1(config)#ip dhcp pool CCNA

R1(dhcp-config)#network 1.0.0.0 255.0.0.0

R1(dhcp-config)#default-router 1.0.0.1

R1(dhcp-config)#ip dhcp excluded-address 1.0.0.1

 DHCP POOL creation for network 5.0.0.0 and POOL CCNP.

R1(config)#ip dhcp pool CCNP

R1(dhcp-config)#network 5.0.0.0 255.0.0.0

R1(dhcp-config)#default-router 5.0.0.1

R1(dhcp-config)#ip dhcp excluded-address 5.0.0.1

 DHCP POOL creation for network 4.0.0.0 and POOL CCIE

R1(config)#ip dhcp pool CCIE

R1(dhcp-config)#network 4.0.0.0 255.0.0.0

R1(dhcp-config)#default-router 4.0.0.1

R1(dhcp-config)#ip dhcp excluded-address 4.0.0.1

Step 5: Setup IP helper Address on Router R2:

R2(config)#int fa0/0

R2(config-if)#ip helper-address 2.0.0.1

Step 6:Setup IP helper Address on Router R3:

R3(config)#int fa0/0

R3(config-if)#ip helper-address 2.0.0.1

R3(config-if)#

Step 7:Check DHCP IP bindings list on router R1 on which DHCP has been configured.

R1#show ip dhcp binding

IP address Client-ID/ Lease expiration Type

Hardware address

1.0.0.2 0060.47CB.8AD4 -- Automatic

1.0.0.3 00D0.FF2C.57AB -- Automatic

1.0.0.4 000C.856B.7ABC -- Automatic

5.0.0.2 00E0.B092.E710 -- Automatic

5.0.0.3 0060.479A.5982 -- Automatic

5.0.0.4 0002.17E1.A958 -- Automatic

4.0.0.2 000A.41B4.C278 -- Automatic

4.0.0.3 0006.2A73.A1EB -- Automatic

4.0.0.4 00D0.D379.3AB8 -- Automatic

R1#

 

DHCP Troubleshooting commands:

 

1.exclude range of ip address from any pool

#ip dhcp excluded-address 1.0.0.1 1.0.0.100

 

2.Exclude only one ip from POOL.

#ip dhcp excluded-address 1.0.0.1

 

3. Check different dhcp related information:

#show ip dhcp binding

#show ip dhcp binding 1.0.0.3

#clear ip dhcp binding 1.0.0.1

(this command will clears an automatic address from the dhcp server database)

 

#clear ip dhcp binding  *

#clear ip dhcp conflict

#clear ip dhcp conflict 1.0.0.1

#clear ip dhcp conflict  *

#show ip dhcp database

#show ip dhcp server statistics

#clear ip dhcp server statistics

 

Note: Few of troubleshooting command will not work in packet tracer but all these commands will work perfectly on real cisco router and also inside GNS3.