Running DHCP on multiple networks

Running DHCP on Multiple Networks

Step 1: Configure router interfaces with appropriate ip address like in a topology
Router R1,
In global configuration mode,
R1(config)#interface fastethernet0/0
R1(config-if)#ip address 10.0.0.1 255.0.0.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface serial 2/0
R1(config-if)#ip address 20.0.0.1 255.0.0.0
R1(config-if)#clock rate 64000
R1(config-if)#encapsulation ppp
R1(config-if)#no shutdown
R1(config-if)#exit
Router R2,
In Global configuration mode,
R2(config)#interface serial 2/0
R2(config-if)#ip address 20.0.0.2 255.0.0.0


R2(config-if)#encapsulation ppp
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface fastethernet 0/0
R2(config-if)#ip address 30.0.0.1 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface fastethernet 1/0
R2(config-if)#ip address 40.0.0.1 255.0.0.0
R2(config-if)#no shutdown

R2(config-if)#exit
Step 2: Connecting the networks using RIP
In Router R1,
Global config mode,
R1(config)#router rip
R1(config-router)#network 10.0.0.0
R1(config-router)#network 20.0.0.0
R1(config-router)#exit
In Router R2,
Global config mode,
R2(config)#router rip
R2(config-router)#network 20.0.0.0
R2(config-router)#network 30.0.0.0
R2(config-router)#network 40.0.0.0
R2(config-router)#exit
Step 3:Configure router interfaces with 'ip helper-address'
We need to configure ip address for the gateway of our network. In this network topology we
need configure Interface fastethernet0/0 in R1 and Interface fastethernet 0/0 in R2 with 'ip
helper-address'. DHCP uses flooded Broadcast (i.e. 255.255.255.255 ) this can be forwarded
from one network to another. We tell the router by giving ip address('ip helper-address') to
forward the packet to the DHCP server if any packet arrived with this broadcast address
255.255.255.255.


In R1,
R1(config)#interface fastethernet0/0
R1(config-if)#ip helper-address 40.0.0.10
R1(config-if)#exit
In R2,
R2(config)#interface fastethernet0/0

R2(config-if)#ip helper-address 40.0.0.10
R2(config-if)#exit
Step 4:Now, Add the network pool to DHCP server, and add 10 and 30 network.
Click on Server->Config->DHCP, there you can see default pool for 40 network 'when we
configure ip address to fastethernet of dhcp server, it will add the network automatically to
default pool by seeing the ip address that belongs to.
Now, Add the network pool for 10 and 30 network
Network pool for 10 Network,Just edit
PoolName->10Network
Default Gateway->10.0.0.1
DNS Server->40.0.0.10
Start IP Address->10.0.0.10
Subnetmask->255.0.0.0
Maximum Number of users->100
TFTP Server->40.0.0.10
then click on 'Add' .
Network pool for 30 Network,
PoolName->30Network
Default Gateway->30.0.0.1
DNS Server->40.0.0.10
Start IP Address->30.0.0.10
Subnetmask->255.0.0.0
Maximum Number of users->100
TFTP Server->40.0.0.10
then click on 'Add' and save.