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Allowing DHCP request to Firewall

ahologounis
Aug 27 06:33:38 fw kernel: UDP Drop: IN=eth1 OUT= MAC=ff:ff:ff:ff:ff:ff:00:05:5f:ed:28:54:08:00 SRC=10.113.192.1 DST=255.255.255.255 LEN=342 TOS=0x00 PREC=0x00 TTL=255 ID=13166 PROTO=UDP SPT=67 DPT=68 LEN=322 

The Source address is my ISP DHCP server. I probably need to allow this into the firewall. I am not sure how to handle the destination address which is a broadcast(?)

Can someone step me through the rule procedure?


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  • 0
    You should block these requests from your ISP. It is always a good idea to drop broadcast requests from your internal network and also your external network. this may help.
    define networks as follows

    LanBroacast x.x.x.255 255.255.255.255
    WorldBroadcast 255.255.255.255 255.255.255.255

    the x= your internal network

    Define filter rules for the following.

    ext_Interface any WorldBroadcast drop
    Int_network any LanBroadcast drop

    Hope you get the idea. I hope this helps
  • 0 in reply to jmartos
    Thanks...It looks like ASL is blocking UDP broadcasts from the INTERNAL to the EXTERNAL network.

    As for my ISP sending me DHCP broadcasts oon port 67/68....I wasn't sure if I was supposed to get them or not....by default they where blocked...I deactivated the rule I created to accept them...

    Whats bothersome is that they are so persistant...I get them every few seconds.

    Anyways, they are blocked now. Thanks for the help.
  • 0 in reply to ahologounis
    You may still want to add the rules as I gave them to you. That will keep the log messages from appearing on you log files.
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