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New Member

DHCP Server priority choice

Hi expert,

Refer to my attached diagram, Can I setup that when LAN user want to get IP address from DHCP server, first choice will query 192.168.1.1 dhcp server. Once 192.168.1.1 dhcp server is down, then will query 172.16.1.1 dhcp server.

thank you

7 REPLIES
New Member

Re: DHCP Server priority choice

Dear,

Yes you can.

For this you need to add following cmd on LAN segment vlan int.

int vlan XX

ip address ...................

ip helper-address 192.168.1.1

ip helper-address 172.16.1.1

If you have any doubt, pls post config.

than I can tell you where exactly need to add these cmds.

Hope this will help you

Rate the post if it will help you.

Regards

New Member

Re: DHCP Server priority choice

Dear sir,

You mean below configuration can make me to request dhcp request from 192.168.1.1 first, once 192.168.1.1 server is down, it will drop to the second one

172.16.1.1 ?

My configuration is

int vlan 100

ip address 100.100.100.1 255.255.255.0

ip helper-address 192.168.1.1

ip helper-address 172.16.1.1

Then if I change to

int vlan100

ip address 100.100.100.1 255.255.255.0

ip helper-address 172.16.1.1

ip helper-address 192.168.1.1

that means first query dhcp server 172.16.1.1 first, once 172.16.1.1 is down, it will query to 192.168.1.1 ?

Any document has publish  it ?

Thanks!

Hall of Fame Super Silver

Re: DHCP Server priority choice

Unfortunately Dipesh is incorrect when he says that you can specify a DHCP server to querry first. If you configure 2 ip helper address commands then IOS will forward requests to both of them. It is likely that both will respond and in that case the client usually accepts the first one that responds. There is not a way in IOS to achieve what you want, that the request will go to a primary and only if that one is down will go to a secondary.

HTH

Rick

New Member

Re: DHCP Server priority choice

Dear sir,

You mean there is no way to control what is first and what is second, Client receive IP address is base on which dhcp respond is faster. Am I right ?

Hall of Fame Super Silver

Re: DHCP Server priority choice

Yes you are right. With ip helper-address there is not a way to establish priority.

HTH

Rick

New Member

Re: DHCP Server priority choice

Dear,

I am not saying the priority of helper address.

But the reachability to DHCP server.

Suppose One DHCP server is in other segment and one DHCP server in the sane local segment than the dhcp server in the local segment will reponse first.

for 172.X.X.1 is other side of router so it will be reached second. 1st will use the dhcp server on local segment and if it will down than go for second one.

Regards,

New Member

Re: DHCP Server priority choice

Reachability could be checked by SLA. May be it is possible to do anything this way?

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