SRX DHCP Relay to Cisco WLC - DHCP issue?

Hi,

I currently have an issue that I am trying to get to the bottom of. I have clients in Subnet X and a Cisco WLC in subnet Y acting as a DHCP server for the IP address of subnet X.

The L3 device is a Juniper SRX 340: with the following relay config:

set forwarding-options helpers bootp server (DHCP-SERVER) set forwarding-options helpers bootp interface (SUBNET-X-GW-IRB)

Clients in subnet X cannot seem to get Ip addresses from the WLC - I have ran a few debugs and get the following output: -

DHCP Server: Nov 15 09:38:49.978: Dropping packet from <SRX-MGMT-LOOPBACK> (unable to match to a dhcp scope) DHCP Server: Nov 15 09:38:57.135: dhcpd: Received 300 byte dhcp packet from 0x0afa6325 <SRX-MGMT-LOOPBACK>:67 DHCP Server: Nov 15 09:38:57.135: Dropping packet from <SRX-MGMT-LOOPBACK> (unable to match to a dhcp scope) DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP received op BOOTREQUEST (1) (len 556,vlan 210, port 2, encap 0xec00, xid 0xef071f00) DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP option len (including the magic cookie) 320 DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP option: message type = DHCP DISCOVER DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP option: 57 (len 2) - skipping DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP option: 61 (len 7) - skipping DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP option: hostname = 25119969 (len 8) DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP option: 55 (len 4) - skipping DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP options end, len 320, actual 64 DHCP Socket Task: Nov 15 09:38:57.755: 54:e1:40:35:d2:af DHCP dropping packet (no mscb) found - (giaddr 0.0.0.0, pktInfo->srcPort 68, op: 'BOOTREQUEST') DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP received op BOOTREQUEST (1) (len 296,vlan 50, port 1, encap 0xec00, xid 0xef071f00) DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP option len (including the magic cookie) 60 DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP option: message type = DHCP DISCOVER DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP option: 57 (len 2) - skipping DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP option: 61 (len 7) - skipping DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP option: hostname = 25119969 (len 8) DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP option: 55 (len 4) - skipping DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP option: 82 (len 13) - skipping DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP options end, len 60, actual 64 DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP received a REQUEST from Gateway SUBNET-X-GW-IRB -- bouncing to local DHCP server. DHCP Socket Task: Nov 15 09:38:57.757: 54:e1:40:35:d2:af DHCP sending to local dhcp server (<SRX-MGMT-LOOPBACK>:67 -> 10.174.8.2:1067, len 300) DHCP Server: Nov 15 09:38:57.757: dhcpd: Received 300 byte dhcp packet from 0x0afa6325 <SRX-MGMT-LOOPBACK>:67

I wonder if the SRX is changing the source IP address of the DHCP requests to its mgmt loopback interface hence the line:

DHCP Server: Nov 15 09:38:57.135: Dropping packet from <SRX-MGMT-LOOPBACK> (unable to match to a dhcp scope)

can anyone else shed any light on this - this setup was working before when the L3 was handled by a cisco L3 switch??