DD-WRT Kong DHCP Lease Renewal Problem FIXED

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phillil's picture
DD-WRT Kong DHCP Lease Renewal Problem FIXED


I'm relatively new to the world of hacking my router, and if it wasn't for sites like this then I wouldn't have got anywhere, so thanks for all the help.

I have been experimenting with both Kong and Voxel f/w, and have eventually decided on Kong for now, and have now noticed a very frustrating issue that I have thankfully fixed, therefore thought I would share


I am connecting to SKY FIBRE, and I appeared to be losing the connection randomly. But I noticed it was actually due to the DHCP lease expiring every hour. So after much reading on various other sites and the DD-WRT Wiki have found a solution.

I have quoted from this forum/post (so credit elsewhere), but thought I'd repeat some important points;


  • It appears that by default DD-WRT firewall blocks all random incoming traffic, unless the router itself has sent out a request first
  • In the case of renewing a DHCP lease, your ISP will send a renewal (to port 68), but it gets blocked because your router never requested it
  • The lease will therefore expire causing the router to lose connection (and in my case causing issues on the LAN)

So the way fo fix it is to execute a script to manually open up the required ports to allow incoming traffic from your ISP;

iptables -I INPUT -p udp --sport 67 --dport 68 -j ACCEPT

I have manually run this in the DD-WRT WebGUI command shell, but plan to save it in the "Save Firewall" section so it runs automatically

So far, my router has maintained connection for a few days, so hopefullt the issue is fixed

kamoj's picture
Thank you, ver useful

Thank you, ver useful information!