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Extended ACL to block udp port 67 68 (dhcp requests)

I have a 2621 router and I'm trying to write an extended Access List to block UDP requests incoming from an outside port. I have tried several times and am still not able to successfully block the udp request. Can anyone give me some ideas on what to try next. Thanks, ~zo

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New Member

Re: Extended ACL to block udp port 67 68 (dhcp requests)

Nevermind, I fixed it myself. Want to know how?? This is how I did it.

I simply wrote an extended acl to deny udp port 68 from any source to any destination on my outside port. ( Not the local subnet). After I did that I went to the global interface command of the outside port and designated the ip directed broadcast to my extended firewall.....and waaa laaaa it works. All local clients from the local subnet can obtain an IP via dhcp, but all dhcp broadcasts from the outside LAN cannot. Which is exactly what I wanted to accomplish because when I took this particular router off the T-1 and onto the Fiber link, It started leasing IP's to the wrong subnet. (the outside port). This Access-List that I wrote now solves the problem. So, since I'm the only one who responded to my very own question, I say thanks to no-one because I solved it all myself.

~zo

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