Users not getting IP from QIP server

[riyasrasheed]

Dear Friends,

Need your advice on this issue.

Users of our new site complained of not getting IP dynamically from DHCP server. Static IPs works fine.

The LAN interface of the router is configured with helper IP address of QIP servers.

On the router there exists a DHCP pool configuration, later we removed this config understanding the helper address will

assign the ip address dynamically.

QIP which serves as DHCP is confgured to assign the IPs, but the users complined of not getting IPs including IP phones.

Kindly advice what could be possible chances of this issue.

Thanks in advance

rYs

[Nael Mohammad · Accepted solution]

New site, new scope, static works but dynamic does not implies a firewall/acl issue. Check to ensure that DHCP server and DHCP traffic is being allowed.

[riyasrasheed]

HI Nael,

Both the DHCP server and traffic are allowed, I m able to ping to the servers from the router.

The users starts getting the IPs after i configure the DHCP pool on the router, but it is not advisable as per the company standared and make no sense to the ip helper address configurations.

Kindly advice.

Thanks

Riyas

[Nael Mohammad]

You need to have the ip helper address configured to relay the DHCP packets to the DHCP server. Without that, how is it going to know where to route DHCP traffic?

[riyasrasheed]

HI Nael,

The IP helper addresses are already in place.

it works fine when i configure a DHCP pool on the router, but once i remove the pool, the users wil face the same problem.

Thanks

Riyas Rasheed

[Nael Mohammad]

You cant have both the ip helper-address and a DHCP pool configured on the router. Basically what happens is the client DHCPDISCOVER will pick the first DHCP server that answers it and in this case its the the router. If you want to pass traffic all the way to the DHCP server, you need to disable the DHCP server on the router and leave only the ip helper-address configured so it can relay the broadcast to the defined DHCP server.

It sounds like you have this current topology for your DHCP server that is working:

Client       ------------>DHCPDISCOVER ---> Router(DHCP Server)

               <------------DHCPOFFER

               ------------>DHCPREQUEST

               <------------DHCPACK

You want to configure your QIP DHCP Server to respond to DHCPDISCOVER, you will need to remove the DHCP pool from the router and add "ip helper-address x.x.x.x" where x.x.x.x is your DHCP server ip.

If that still does not work, you will need to check the configuration on your DHCP server to ensure its not mis-configured. QIP is not a cisco product but you should be able to view debugs on that application to identify if the DHCP server is sending an offer or dropping the request. Most likely your scopes are mis-configured on the server.