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Date:      Tue, 2 Jan 2007 21:06:40 +0100
From:      "Jurjen Middendorp" <jurjenm@stack.nl>
To:        freebsd-questions <freebsd-questions@freebsd.org>
Subject:   ipfw denies everything and i can open websites?
Message-ID:  <20070102200640.GA7476@jurjenm.stack.nl>

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Hello, 
i have configured my firewall, but after i do "ipfw -q flush" i am still
able to visit websites, download my e-mail, etc. I thought the default action of
ipfw was to deny everything and ipfw show confirms that... Why am i able to go
on the internet? Is this weird behaviour or is there something i don't
understand about ipfw/firewalls??
I am behind a router (NAT) and get my ip with dhcp.

Here is a litle log from what happens if i try to open a random website
(blah.org) after i disable my firewall.

[jurjen@jurjen ~]$ su
Password:
[root@jurjen /home/jurjen]# fw_uit
65535 2 616 deny ip from any to any
[root@jurjen /home/jurjen]# tcpdump
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ath0, link-type EN10MB (Ethernet), capture size 96 bytes

20:41:44.919465 IP jurjen.lan.55071 > SpeedTouch.lan.domain:  4879+ A? blah.org. (26)
20:41:45.062650 IP SpeedTouch.lan.domain > jurjen.lan.55071:  4879 1/0/0 A 205.150.150.140 (42)
20:41:45.062889 IP jurjen.lan.53038 > SpeedTouch.lan.domain:  4880+ AAAA? blah.org. (26)
20:41:45.173416 IP SpeedTouch.lan.domain > jurjen.lan.53038:  4880 0/1/0 (98)
20:41:45.173790 IP jurjen.lan.56029 > 205.150.150.140.http: S 1223552665:1223552665(0) win 65535 <mss 1460,nop,wscale 1,nop,nop,timestamp 21149548 0,sackOK,eol>
20:41:45.288590 IP 205.150.150.140.http > jurjen.lan.56029: S 3294004362:3294004362(0) ack 1223552666 win 16384 <mss 1460,nop,wscale 0,nop,nop,timestamp 0 0,nop,nop,sackOK>
20:41:45.288662 IP jurjen.lan.56029 > 205.150.150.140.http: . ack 1 win 33304 <nop,nop,timestamp 211496620>
20:41:45.288924 IP jurjen.lan.56029 > 205.150.150.140.http: P 1:395(394) ack 1 win 33304 <nop,nop,timestamp 21149663 0>
20:41:45.441225 IP 205.150.150.140.http > jurjen.lan.56029: . 1:1449(1448) ack 395 win 65141 <nop,nop,timestamp 1951517 21149548>
20:41:45.442758 IP 205.150.150.140.http > jurjen.lan.56029: P 1449:2533(1084) ack 395 win 65141 <nop,nop,timestamp 1951517 21149548>
20:41:45.442812 IP jurjen.lan.56029 > 205.150.150.140.http: . ack 2533 win 32762 <nop,nop,timestamp 21149817 1951517>
20:41:45.591472 IP jurjen.lan.56029 > 205.150.150.140.http: P 395:720(325) ack 2533 win 33304 <nop,nop,timestamp 21149965 1951517>
20:41:45.760525 IP 205.150.150.140.http > jurjen.lan.56029: P 3981:4328(347) ack 720 win 64816 <nop,nop,timestamp 1951520 21149965>
20:41:45.760603 IP jurjen.lan.56029 > 205.150.150.140.http: . ack 2533 win 33304 <nop,nop,timestamp 21150134 1951517,nop,nop,sack 1 {3981:4328}>
20:41:45.763003 IP 205.150.150.140.http > jurjen.lan.56029: . 2533:3981(1448) ack 720 win 64816 <nop,nop,timestamp 1951520 21149965>
20:41:45.763045 IP jurjen.lan.56029 > 205.150.150.140.http: . ack 4328 win 32406 <nop,nop,timestamp 21150137 1951520>
20:41:46.021900 IP jurjen.lan.62273 > SpeedTouch.lan.domain:  23988+ PTR? 140.150.150.205.in-addr.arpa. (46)
20:41:46.255700 IP SpeedTouch.lan.domain > jurjen.lan.62273:  23988 NXDomain 0/1/0 (117)
20:42:02.361174 IP sys00.lan.netbios-dgm > 10.0.0.255.netbios-dgm: NBT UDP PACKET(138)

And the website has loaded... how is this possible??

greets, jurjen



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