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Linux IPTABLES help

 
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Old 06-18-2005
Linux IPTABLES help
I'm new to Linux and I made a big mistake at work recently locking myself out of our own server Smilie.

I did iptables -F first as the tutorial said and then entered the rules. I wanted to start over again so I did iptables -F and it locked us out. We had to get someone to physically restart iptables before we could get back in.

Any idea why the second iptables -F locked me out and how to avoid it and know when it will flush everything and when it will lock out?

Thanks

I used some rules I saw in a tutorial as follows:
iptables -F
iptables -A INPUT -I lo -p all -j ACCEPT
iptables -A OUTPUT -o lo -p all -j ACCEPT
iptables -A INPUT -I eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p tcp --tcp-option ! 2 -j REJECT --reject-with tcp-reset
iptables -A INPUT -p tcp -I eth0 --dport 22 -j ACCEPT
iptables -A INPUT -p udp -I eth0 --dport 22 -j ACCEPT
iptables -A INPUT -p tcp -I eth0 --dport 80 -j ACCEPT
iptables -A INPUT -p udp -I eth0 --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -I eth0 --dport 53 -j ACCEPT
iptables -A INPUT -p udp -I eth0 --dport 53 -j ACCEPT
iptables -P INPUT DROP
 
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LEARN ABOUT OPENDARWIN

iptables-save

IPTABLES-SAVE(8)						  iptables 1.6.1						  IPTABLES-SAVE(8)

NAME

       iptables-save -- dump iptables rules to stdout

       ip6tables-save -- dump iptables rules to stdout

SYNOPSIS

       iptables-save [-M modprobe] [-c] [-t table]

       ip6tables-save [-M modprobe] [-c] [-t table]

DESCRIPTION

       iptables-save  and ip6tables-save are used to dump the contents of IP or IPv6 Table in easily parseable format to STDOUT. Use I/O-redirect-
       ion provided by your shell to write to a file.

       -M, --modprobe modprobe_program
	      Specify the path to the modprobe program. By default, iptables-save will inspect /proc/sys/kernel/modprobe  to  determine  the  exe-
	      cutable's path.

       -c, --counters
	      include the current values of all packet and byte counters in the output

       -t, --table tablename
	      restrict output to only one table. If not specified, output includes all available tables.

BUGS

       None known as of iptables-1.2.1 release

AUTHORS

       Harald Welte <laforge@gnumonks.org>
       Rusty Russell <rusty@rustcorp.com.au>
       Andras Kis-Szabo <kisza@sch.bme.hu> contributed ip6tables-save.

SEE ALSO

       iptables-apply(8),iptables-restore(8), iptables(8)

       The  iptables-HOWTO, which details more iptables usage, the NAT-HOWTO, which details NAT, and the netfilter-hacking-HOWTO which details the
       internals.

iptables 1.6.1															  IPTABLES-SAVE(8)