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Cisco IOS DHCP server - Handling the receiving of unicasts?

Is the Cisco IOS DHCP server capable to handle DHCPDiscover/Requests not as broadcasts but as unicast packets? Is this a configuration issue? Why this question? We test in a Wireless environment the AIRESPACE solution with IOS DHCP server on routers. We found out, that the AIRESPACE controller needs to act as an relay agent (otherwise he doesn't forward these packets). The result is that the DHCPDiscover is correctly converted to an unicast and sent to the IOS DHCP server, but this guy ignores these packets. Note: We need to have the IOS DHCP server running on routers in this environment.

Any ideas? Thanks in advance.

Raffael

6 REPLIES

Re: Cisco IOS DHCP server - Handling the receiving of unicasts?

Yes, Cisco IOS DHCP server can handle the DHCP unicast packets.

Do you have any option in AIRESPACE controller to add the DHCP address.If you have that option make sure that DHCP server IP is there and its enabled.

-amit singh

Community Member

Re: Cisco IOS DHCP server - Handling the receiving of unicasts?

Hi Amit

I'm not really sure if I understand you correctly. Let me explain the following things: The DHCP server address is already added (to activate the dhcp relay function) on the Airespace controller. But the existing configuration on the IOS dhcp server, which is laying on the router doesn't work for this. Can you explain to me, if possible which parameters are to be added/changed in the configuration? Thanks a lot. -Raffael

Re: Cisco IOS DHCP server - Handling the receiving of unicasts?

Please paste the route configuration.

-amit singh

Community Member

Re: Cisco IOS DHCP server - Handling the receiving of unicasts?

Hi Amit

Thereby the dhcp part of a router:

ip dhcp pool ACME

network 10.21.190.128 255.255.255.128

domain-name pwlan-acme.com

dns-server 10.192.20.10 10.192.20.11

default-router 10.21.190.129

lease 0 0 15

update arp

accounting DHCP

! *** end ***

Can you tell me which of the config possibilities will solve my problem?:

acme-xyz(dhcp-config)#?

DHCP pool configuration commands:

accounting Send Accounting Start/Stop messages

bootfile Boot file name

class Specify a DHCP class

client-identifier Client identifier

client-name Client name

default-router Default routers

dns-server DNS servers

domain-name Domain name

exit Exit from DHCP pool configuration mode

hardware-address Client hardware address

host Client IP address and mask

import Programatically importing DHCP option parameters

lease Address lease time

netbios-name-server NetBIOS (WINS) name servers

netbios-node-type NetBIOS node type

network Network number and mask

next-server Next server in boot process

no Negate a command or set its defaults

option Raw DHCP options

origin Configure the origin of the pool

subnet Subnet allocation commands

update Dynamic updates

utilization Configure various utilization parameters

vrf Associate this pool with a VRF

acme-xyz(dhcp-config)#

Thank you

-Raffael

Community Member

Re: Cisco IOS DHCP server - Handling the receiving of unicasts?

Hi

It's a long time since I've read/heard about this. So, is it possible to get some input concerning this topic? I'd appreciate to get any updates. Thanks in advance

-Raffael

Cisco Employee

Re: Cisco IOS DHCP server - Handling the receiving of unicasts?

Hi Raffael,

Do you know for sure if the DHCP server is receiving the DHCP discover frames and whether a DHCP offer is sent?

Try running a debug to verify:

debug ip dhcp server events

debug ip dhcp server packets

This should be safe to run as long as your DHCP clients aren't in the range of thousands or more.

It may be helpful to have a test PC to release/renew so that you can watch for information for that specific machine.

HTH,

Bobby

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