I want to block DHCP Server

[BERNHARD FIEGLMUELLER]

Hi i want to block on an ap where wlan clients are connected, dhcp server from the clients. bc the clients are getting the ip from my dhcp server. but when he also starts an dhcp server i ahve two server in my wlan. so i want to block dhcp ports on my ap.

i have tried it:

i made an port filter: port 67 and 68 (bootp server and client) then i places the filter on RADIO recive site. but then the client doenst get an ip. so i tried it only with port 67 or 68 it also doesnt work.

hope anybody can help me with this issue.

regards Bernhard

[BERNHARD FIEGLMUELLER]

doesnt anybody have the same issue? cant anybody helpme.

bernhard

[rslaski]

DHCP client requests are sent from DHCP client (68) to server's DHCP server port (67). Server replies using port 67 to client's port 68. All above are UDP obviously. So to block rogue DHCP servers put an input ACL 'deny any eq 68 any' to AP radio interface and this should work. Also remember that DHCP client for initial message exchanges uses 0.0.0.0 as src IP and 255.255.255.255 as dest IP so do not replace 'any' with your IP subnets. Hope this helps.