DHCP Client not responding to Offer

josephreid · ‎02-24-2005

I've set up a single firewall with 1 B class network, with 4 subnets on the inside and 1 C class network in the DMZ.They are connected to an external network. Have initiated DHCPRelay in C class interface, with helper address and DHCP Server in B class network. Problem is, Discover and Offer occur, so I know that the relay is talking to the server and the server is replying. Problem is it then vanishes into the ether. Theres no request or a decline. If I put a server into the C class network, it works fine. Or if we build and configure in internal network and then move into DMZ, it works, But I really need ot be able to build an boot-up of the DMZ machines. Any ideas,

scoclayton · ‎02-24-2005

How are you determining that the DHCPOFFER and DHCPREQUEST are being properly sent? Do you have a scope on your DHCP server than includes the address that is configured on the Class C interface of the PIX?

Scott

josephreid · ‎02-25-2005

Monitoring the connection as its being made. Seeing the DISCOVER and OFFER being sent from the logs. Also seeing the UDP connection being built and torn down on the DHCP Server. We have Server running on a Linux server, the IP's are a static allocation. If we run DHCPRelay on a linux server on the Class C network, everything works fine. The client makes DHCPREQUEST and then we see DHCPACK. It's only when we use CISCO's DHCPRELAY on the PIX that the problem occurs.

iswift · ‎03-22-2005

Did you ever resolve your issue ?

My clients exhibit the same behaviour.

My situation is class C throughout, so no vlsm needed here although that shouldn't be a problem methinks.

As per yours we see DISCOVER and OFFER being sent, and the clients just seem to time out.

Again like you, if I take out the PIX and use straight L2/L3 connectivity then everything works fine via the ip-helper process.

# sh dhcpr stat

Packets Relayed

BOOTREQUEST 0

DHCPDISCOVER 90

DHCPREQUEST 0

DHCPDECLINE 0

DHCPRELEASE 0

DHCPINFORM 0

BOOTREPLY 0

DHCPOFFER 90

DHCPACK 0

DHCPNAK 0

We also see multiple requests to port 4011 which is more of a mystery as that is the net-boot (PXE) port.

710005: UDP request discarded from 169.254.6.107/68 to wlan182:255.255.255.255/4011