Here's the whole scenario in this link:
http://www.linuxquestions.
I can't see where the mistake is in my iptables firewall.
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Judging by that posting you're problem is not IP tables related. In the second to last post you switch off IPTables & still have the problem (did you confirm that iptables was actually off?) Assuming iptables was off and the problem still existed, I'd use a packet capture program like wireshark & capture what happens during the conversation. The problem could be anywhere in the network path.
Here's the iptables:
#!/bin/bash
# Location in which iptables initscript will save set rules on
# service shutdown
#IPTABLES_SAVE="/var/lib/i
# Options to pass to iptables-save and iptables-restore
#SAVE_RESTORE_OPTIONS="-c"
# Save state on stopping iptables
#SAVE_ON_STOP="yes"
# External Network Interface
SKYWAY="eth0"
# Internal Network Interface
LAN1="eth1"
# Internal Subnet
SUBNET1="192.168.195.0/24"
IPT="/usr/sbin/iptables"
MPROBE="/sbin/modprobe"
echo "Flush any/all rules previously existing."
echo "Set policies."
$IPT -t filter -F
$IPT -t filter -X
$IPT -t nat -F
$IPT -t nat -X
$IPT -P INPUT DROP
$IPT -P OUTPUT DROP
$IPT -P FORWARD DROP
echo "Reload necessary modules."
$MPROBE ip_tables
$MPROBE nf_conntrack
$MPROBE nf_conntrack_ipv4
$MPROBE nf_nat
$MPROBE xt_state
$MPROBE xt_tcpudp
$MPROBE ipt_REJECT
$MPROBE ipt_LOG
$MPROBE ipt_state
$MPROBE ipt_MASQUERADE
$MPROBE ip_conntrack
$MPROBE ip_conntrack_ftp
$MPROBE iptable_mangle
$MPROBE iptable_nat
$MPROBE iptable_filter
echo "lo"
$IPT -t filter -A INPUT -i lo -j ACCEPT
$IPT -t filter -A OUTPUT -o lo -j ACCEPT
echo "input"
$IPT -t filter -A INPUT -i $SKYWAY -m state --state RELATED,ESTABLISHED -j ACCEPT
$IPT -t filter -A INPUT -i $SKYWAY -p tcp -m state --state NEW --dport 22 -j ACCEPT
$IPT -t filter -A INPUT -i $LAN1 -j ACCEPT
$IPT -t filter -A INPUT -p icmp -m limit --limit 30/minute --limit-burst 2 -j ACCEPT
echo "ouput"
$IPT -t filter -A OUTPUT -o $SKYWAY -j ACCEPT
$IPT -t filter -A OUTPUT -o $LAN1 -j ACCEPT
$IPT -t filter -A OUTPUT -p icmp -m limit --limit 30/minute --limit-burst 2 -j ACCEPT
echo "forward"
$IPT -t filter -A FORWARD -i $LAN1 -j ACCEPT
$IPT -t filter -A FORWARD -o $LAN1 -j ACCEPT
$IPT -t filter -A FORWARD -i $SKYWAY -j ACCEPT
$IPT -t filter -A FORWARD -o $SKYWAY -j ACCEPT
$IPT -t filter -A FORWARD -i $LAN1 -s $SUBNET1 -j ACCEPT
$IPT -t filter -A FORWARD -p icmp -m limit --limit 30/minute --limit-burst 2 -j ACCEPT
echo "prerouting/postrouting"
$IPT -t nat -A POSTROUTING -o $SKYWAY -s $SUBNET1 -j MASQUERADE
echo 1 > /proc/sys/net/ipv4/ip_forw
echo "Netfilter framework is set."
From LAN client:
bash-3.1# nmap -p 80 linuxquestions.org
Starting Nmap 5.00 ( http://nmap.org ) at 2009-09-17 11:34 EDT
Interesting ports on www.linuxquestions.org (75.126.162.205):
PORT STATE SERVICE
80/tcp open http
Nmap done: 1 IP address (1 host up) scanned in 1.29 seconds
bash-3.1#
Here's some traceroute info done from linux notebook connected as client on LAN interface:
1. Result of "traceroute 192.168.195.1" (the LAN interface):
1 192.168.195.1 (192.168.195.1) 0.350 ms 0.218 ms 0.199 ms
- - - - - - - -
2. Result of "traceroute 75.67.115.103" (the Internet interface):
1 c-75-67-115-103.hsd1.ct.co
Am I seeing a problem here? Shouldn't this be 2 hops -- 1 to LAN nic, and 2 to WAN nic? Or am I misunderstanding the output?
- - - - - - - - -
3. Result of "traceroute linuxquestions.org":
1 192.168.195.1 (192.168.195.1) 0.297 ms 0.212 ms 0.198 ms
2 73.156.184.1 (73.156.184.1) 18.924 ms 7.402 ms 13.502 ms
3 68.85.143.157 (68.85.143.157) 84.242 ms 33.042 ms 19.686 ms
4 po-22-rr01.wallingford.ct.
5 po-51-ar01.berlin.ct.hartf
6 be-10-ar01.chartford.ct.ha
7 pos-2-4-0-0-cr01.newyork.n
8 pos-1-12-0-0-cr01.mclean.v
9 pos-1-10-0-0-cr01.atlanta.
10 pos-1-15-0-0-cr01.dallas.t
11 softlayer-cr01.dallas.tx.i
12 po2.dar02.dal01.dallas-dat
13 po2.fcr02.dal01.dallas-dat
14 www.linuxquestions.org (75.126.162.205) 69.249 ms 71.201 ms 69.175 ms
- - - - - - - -
Seems logical but again I don't see notation of the hops from LAN nic to WAN nic, and then out to the internet. But not sure if I'm understanding the output correctly.
Solved.
Exhaling. :-)
I was getting desperate, and there it was staring me in the face.
Look at the MTU number on eth0 -- way too low. I've never seen a number as low as that. The lowest I've ever had to tune an MTU is 1412 or 1492 while using DSL service.
I re-set the figure to 1500 - ~$ifconfig eth0 mtu 1500
Went to a LAN client and it worked immediately.
>2. Result of "traceroute 75.67.115.103" (the Internet interface):
>1 c-75-67-115-103.hsd1.ct.co
>Am I seeing a problem here? Shouldn't this be 2 hops -- 1 to LAN nic, and 2 to WAN nic? Or am I >misunderstanding the output?
Nope, this is normal, it's only one hop, both nic on the same device.
Your nat rules seems fine.
Can you elaborate on how your WAN side is connected? EG what line you are using, what router, etc.
Can you also try to run the following command and output the results.
telnet www.linuxquestions.org 80
GET /
Business Accounts
Answer for Membership
by: alvedenPosted on 2009-09-16 at 20:36:36ID: 25352640
Do you mind posting your iptables access rules and nat rules here?