How to get ip From DHCP server Present away From Multiple Networks

Here,we are going to see how to get ip from dhcp that is present away from multiple networks.

Step 1:Create topology like this

Step 2:configure router interfaces with approriate 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 3:Now, I am going to use RIP to enable dynamic routing,for that just add directly connected networks to 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 4: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 5:Now,Add the network pool to DHCP server,I am going 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.

Step 6:Now,From 10 Network click on any PC->Desktop->Ip Configuration->Choose'DHCP'.Now,we will get ip address from dhcp server.

Step 7:Now,From 30 Network click on any PC->Desktop->Ip Configuration->Choose'DHCP'.Now,we will get ip address from dhcp server.