DHCP Request

[gaowen]

Hello all,

Does anyone know if it is possible to request a specific DHCP adddress from the DHCP server on Cisco switches? (15.0.2 C3750V2)

Gareth

[Mark Malone]

Hi
do you mean using client-identifier DHCP where you can make sure a specific ip address from the pool is assigned to a specific host based on there client-id , if that is what your talking about then yes you can do it on 3750

something like
ip dhcp pool my-host
host 10.0.0.100 255.255.255.0
client-identifier 01AA.BBCC.0011.FF

https://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfdhcp.html

[gaowen]

no i mean as a DHCP client, something like

ip address dhcp

ip dhcp request ip 12.1.1.1

[Richard Burts]

Gareth

When a DHCP client is requesting an IP from the server it will typically request to be assigned the IP that it previously used. But I am not aware of any way that you can configure what IP address the client should request.

HTH

Rick

[Muhammad Uzair]

As per my best knowledge and little bit digging in documentation there is no such way " ip dhcp request ip (ip address) ".

DHCP itself means that client start with discover message now its up to you if you want to bind any specific IP address with client MAC because in case of DHCP Reverse ARP is in use where you have the MAC address but you do not have IP address and try to get the one, lets make it short either you can bind the IP address with client MAC so once client will send discover message DHCP server will decide based on MAC (client identifier) and provide the bind address or you can exclude that IP address specifically by doing " IP dhcp exclude-address 10.10.10.5 10.10.10.10 (now in this case from 5 to 10 will not be allocated to any client when he send DHCP discover message).

Dhcp excluding can be done in global with IP DHCP exclude-address while MAC binding can be done inside of DHCP pool by "address 10.10.10.5 hardware-address aa.bb.cc,dd.ee.ff "

Hope that answer the question.

Being a learner if I have any mistake please correct.

Kindest regards,

Uzzi

[gaowen]

Hi all,

I'm asking specifically about the client, not the server. On Windows clients they will request lease extension at t1 and request the same IP as they already have at t2 I think - though this i dont think is true for routers. On windows you can fix the registry to inform the dhcp client that it should request an IP address of your choosing I was wondering if you could do the same for a router. I didn't think so and looks like you can't.

Thanks for the help.

Gareth

[Richard Burts · Accepted solution]

Gareth

Unfortunately I believe that Cisco routers and switches do not have the ability to do what you want.

HTH

Rick

[Deepak Kumar]

I think, there is no solution as you need. But you can archive the same (90%) if your DHCP server in another VLAN using IP helper address, and second option is configure DHCP snooping. 

Regards,

Deepak Kumar