Hi,

I`m stuck and need some help.

I have a Vigor3900 router, AP910C access point and a netgear M4100 switch.
Two VLANs, 10 is the main, 20 is the guest. Both VLANs are setup on the access point which connect through the netgear switch to port1 of the Vigor3900. VLANs are setup on the netgear switch and Vigor router.
DHCP is switched off for VLAN10 and we have a windows 2016 server set up as DHCP and DNS.
DHCP is switch on for VLAN20 on the Vigor3900

The guest wifi works fine and most of the time the main network works through the wifi. I am having a few issues with a few devices not getting an IP from the main network. I can see on the DHCP server on VLAN10 that the DISCOVER and OFFER is getting there but the REQUEST and ACK doesn`t get back to the client's machine.

Any ideas?

Thanks

James

Have you configured DHCP Relay on the 3900? The DHCP request needs to be forwarded to the Windows Server.

https://www.draytek.com/en/faq/faq-connectivity/connectivity.lan/how-to-use-dhcp-relay-over-lan/

Hi,

Thanks for the reply. I can see the discover and offer at the windows server but the request is not getting to the client. I can assume that the windows server is getting the correct information but something is not getting back to the client.

Has DHCP relay been enabled then? The relay agent forwards the DHCP response back to the requesting client.

Cisco has a nice graphic here.

https://www.cisco.com/c/en/us/td/docs/app_ntwk_services/data_center_app_services/ace_appliances/vA1_7_/configuration/routing_bridging/guide/rtbrgdgd/dhcp.html

Hi,

DHCP relay is not enabled as i was under the impression that if the dhcp server was on the same subnet then it would respond to the requests from the client.

Your right, the request should be served if all in the same vlan. Sorry was assuming that your servers and clients would be on separate vlans. If your confident that the vlan configuration is correctly configured on the switch and 3900 id open a ticket with support.