Caution Use this tip only if your machine is not connected to a public network directly Disabling a firewall even for a short while may cause great harm on your machine

Before you decide to flush all firewall rules, you should check whether anything is happening at all. Use the iptables -L command for that; this command gives you an overview of all the rules that are currently active on your machine. If the output looks like Listing 34-2, the problem could be firewall related.

Listing 34-2. Partial Output o/iptables -L on a Configured Firewall

SFO:/ # iptables -L Chain INPUT (policy DROP)

target prot opt

source

destination

ACCEPT all --

anywhere

anywhere

ACCEPT all --

anywhere

anywhere

state

RELATED,ESTAB

LISHED

input ext all --

anywhere

anywhere

input_ext all --

anywhere

anywhere

LOG all --

anywhere

anywhere

limit:

avg 3/min bu

rst 5 LOG level warning tcp-options

ip-options prefix

SSFW2-IN-ILL-

TARGET '

DROP all --

anywhere

anywhere

Chain FORWARD (policy DROP)

target prot opt source destination

ACCEPT all -- anywhere anywhere

LOG all -- anywhere anywhere limit: avg 3/min bu rst 5 LOG level warning tcp-options ip-options prefix SSFW2-FWD-ILL-ROUTING '

Chain OUTPUT (policy ACCEPT)

target prot opt source destination

ACCEPT all -- anywhere anywhere

ACCEPT all -- anywhere anywhere STABLISHED

LOG all -- anywhere anywhere rst 5 LOG level warning tcp-options ip-options prefix sSFW2-OUT-ERROR

state NEW,RELATED,E limit: avg 3/min bu

Chain forward_ext (0 references) target prot opt source

Chain input_ext (2 references) target prot opt source DROP all -- anywhere destination destination anywhere

PKTTYPE = broadcast

However, if you see a list of only the three chains INPUT, FORWARD, and OUTPUT without any further specification, it is useless to disable your firewall. If you do see a lot of output, you can use the rcSuSEfirewall2 stop command, which brings down everything completely. Do a fast check to see whether that made a difference, and use rcSuSEfirewall2 start as fast as you can to bring the firewall up again so you are protected.

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