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DHCP server on routers


I have a routerA and a routerB and a routerC.

RouterC is connected to routerB and routerB is connected to routerA

Q1) Can I configure routerA as a DHCP server, while routerB is the DHCP client taking ip addresses from routerA?

Q2) Can routerB also be configured as DHCP relay to relay dynamic ip addresses from routerA to routerC?

Q3) Finally, if routerB has some ports w/ static ip address, but the port that is used to link routerA is empty waiting for routerA to issue dynamic ip address. Can this be done?

Thank you.




Re: DHCP server on routers


q1 - yes.

router A


Lets configure two pools now. test1 is required to answer Q1, while test2 is required to answer Q2.

ip dhcp pool test1

network /24


lease infinite

ip dhcp pool test2

network /24

default-route <--- ip address of router B

lease infinite

ip dhcp excluded-address

router B

int fa0

ip address dhcp <--- configures as client

q2. Yes - > On the interface that is connected between router B and router C configure a helper address. But you will have to assign a different pool for C.

Assuming Router A is,

int fa0/1

description Interface connected to router C

ip add

ip helper-address

#####make sure you configure this ip address ( as static. Also exclude this address from the DHCP pool in router A.

Router C should be configured with its interface connected to router B as a DHCP client.

interface fa0/1

ip address dhcp

Q3. I am not sure if I understand your question no 3 correctly.



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Community Member

Re: DHCP server on routers

Hi Shanky,

Is a static ip address on routerB connected to routerA?

I was thinking of not configuring any static ip addresses on the routerB at all.

As such, can routerC (also no ip addresses) able to connect to routerB?

RouterC is supposed to get dynamic ip addresses from RouterA via RouterB (which acts as a relay)

Or must routerB's port be static in order for RouterC to connect to it?

In my q3, if routerC has 2 ports, port1 is taking dynamic ip addr from routerB, while port2 is static ip addr for internal LAN.

Can it work?

Thank you.

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