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The issue that I am experiencing is that DHCP requests can't be delivered from DHCP server on sw1 to DHCP client server on sw2 when DHCP snooping is enabled. Client servers on the same switch as DHCP server are able to receive DHCP with no problem. Both switches are connected to a router through which traffic between them is transported. I have seen solutions for Cisco switches, but I am using dell switches and I can not find a solution to this. Disabling DHCP snooping on either of the switches fixes the problem oddly. I've also enabled snooping trust on DHCP server and client ports as well as uplink from sw1 to sw2. I am working with dell S4810 switches. Any suggestions?

UPDATE:

To eliminate the possibility of router issue I did the same thing simply by connecting 2 switches of the same model and of the same configuration with each other and trusting all ports and uplinks for dhcp snooping. My client server is still unable to receive DHCP server reply packet. I tracked packet pathway between switches and noticed that client server is able to send DHCP request packet to the DHCP server which the server receives, however when the DHCP server tries to send a reply, the packet reaches the switch on which the client server resides but it never reaches the client server itself. It seems like the client switch drops the reply packet. With dhcp snooping disabled everything works in order.

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  • "Both switches are connected to a router through which traffic [..] is transported." - DHCP uses a layer 2 broadcast and will not cross a router.
    – Zac67
    Oct 23, 2017 at 10:50

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I was having the same issue with two devices plugged into a single switch. When I turned off DHCP snooping in the switch everything worked. So, firstly, thank you for that.

I then turned DHCP snooping back on but I wasn't able to reproduce the error state. Things now seem to be working. My switch is a Buffalo so maybe there is some quirky firmware on the device.

However, the switch port has to be set to "Trusted" for DHCP, else the switch disallows the DHCP server on that port. According to https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/25ew/configuration/guide/conf/dhcp.html

DHCP snooping acts like a firewall between untrusted hosts and DHCP servers. It also gives you a way to differentiate between untrusted interfaces connected to the end-user and trusted interfaces connected to the DHCP server or another switch.

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