D-Link VPN Router > DSR-250N

Can't get DHCP Relay to work on a DSR-250N router.

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I'm hoping someone can help me solve a problem I'm having with a DSR-250N router.  I'm a network tech working for a local city government.  We have a headquarters at city hall, with several branch offices throughout the city.  Our DHCP and DNS server is all on one server back at city hall, and connected to a layer 3 Cisco switch at city hall. The IP address of the DHCP server is, and our layer 3 switch can route between subnets at city hall and our remote offices.  Our Internet connection is also through this layer 3 switch at city hall.  Our remote offices all connect back to this layer 3 switch, so they get both their DHCP scopes and Internet through the layer 3 switch at city hall.  Here is my problem.  I am trying to set up this DSR-250N router at a remote office.  I set the WAN address to with a /24 subnet and default gateway address of (which is the IP address of the VLAN on the layer 3 switch back at city hall that our remote offices all connect back to, and where the DHCP server is located, on a different VLAN).  The inside or LAN of this remote office has a subnet of with a /24 subnet and the default gateway of the LAN is  I set the routing mode to Classic Routing on the DSR-250N and set the DHCP Mode to DHCP relay, with the gateway address of, which is the IP address of the DHCP server back at city hall.  When I plug in a PC to the switchports of the router and set the NIC to DHCP, nothing happens.  It does not get an IP address in the 10.1.17.X subnet, which indicates to me that DHCP Relay on the DSR-250N isn't working.  Here's the frustrating part.  If I set the NIC to a static IP address in the 10.1.7.X subnet, such as, then everything is fine!  I can ping the LAN side of the DSR-250N, the WAN side, can ping IP addresses back at city hall, can ping all the subnets of our other offices, and can get to the Internet just fine.  When I switch the NIC back to DHCP, I get no IP address at all.  From the DSR-250N, I can get to everything as well (I can PING the Internet, city hall, remote offices, DHCP server address).  Not sure what I'm doing wrong.  All the switchports on the DSR-250N are in the same VLAN (the default VLAN 1).  The WAN configuration is correct.  Everything works great, until I set the DSR-250N to DHCP Relay mode, then I get nothing.  What am I doing wrong?  What do I need to change or configure on the DSR-250N to get the DHCP Relay to work correctly?  Does the DHCP server HAVE to be in the same subnet as the LAN on the DSR-250N?  Our Cisco routers all work fine with DHCP Relay, but I can't get this D-Link router's DHCP Relay to work.  Please Help!


* What Hardware version is your router? Look at sticker under the router case.
* Link>What Firmware version is currently loaded? Found on the routers web page under status.
* What region are you located?
What happens if you don't use DHCP Relay or any relay on the DSR?
Try turning OFF DHCP server on the DSR?

What does the User manual say about setting the DSR up with L3 and other DHCP servers?

The hardware version is B1
The firmware version is the latest version, version 3.12_WW
I am located in the United States.

Can't figure this out.  Static IP addresses of PCs attached to this router work fine, but those set to DHCP do not get an address.  I can ping the IP address of the
DHCP server from the router itself, and from PCs that have a static IP address.  For some reason, the DHCP relay on this router is not working. 

Let me see if we can get some help on this. I'm not familiar with DSR models as they are business class routers. I handle the home class stuff.  ::)


at a first glance I can't see anything that might be obviously wrong, except the term "Gateway" in DHCP Relay mode is quite confusing (shouldn't it be called DHCP Server instead?) ...

Did you configure an additional Scope für within your DHCP-Server (but as a network tech of course you did ...)?
Since Routing seems okay, maybe there are any firewall filtering rules (or Cisco ACLs at the L3 switch) active that cause dropping of 67/udp and/or 68/udp?
Any chance to do some packet sniffing at the uplink interface in order to see if dhcp traffic arrives from branch router DSR-250N?
Any log informatiion available from within the DHCP server why a possibly arrived request for a DHCP lease was eventually refused?


From this link you can find the following statment:

--- Quote ---DHCP Relay: With this option enabled, DHCP clients on the LAN can receive IP address leases and corresponding information from a DHCP server on a different subnet. Specify the Relay Gateway, and when LAN clients make a DHCP request it will be passed along to the server accessible via the Relay Gateway IP address.
--- End quote ---

This sounds like you cannot configure a DHCP server directly but have to relay to an uplink DHCP relay (Relay Gateway) which in turn relays to the DHCP server. Hence if nothing other helps: Configure a Cisco bootp helper (this is the Cisco term for DHCP relay) that listens on interface and specify in the Gateway field for DSR's DHCP Relay mode.


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