On Tue, 23 Sep 2003, Benny Amorsen wrote:

> On 2003-09-23 at 10:50, pineapple wrote:
> 
> > So far my node seems to be working ok as well as my web server, mail
> > server and ftp server.  I didn't consider that these messages could
> > impact my network.  What outside ICMP traffic would you NOT block
> > (besides PMTU as you said)?
> 
> I have not been able to find any consensus on which ICMP packets to
> allow. Personally I allow everything that Linux iptables considers
> related traffic. ICMP is tricky - as an example, Linux iptables /still/
> rejects with port-unreachable when it should reject with
> admin-prohibited.

Eh.  Port-Unreachable says there's nothing there.  Admin-Prohibited says
"something is there that they're blocking us from."

... -j REJECT --reject-with <bla>

I've yet to see the need for a firewall anyway.  The worms come in on
ports that have to be open (25, 80) to machines that have to be on them
(mailserver/webserver) or via someone's laptop.  The only reason I've
even got one up is to NAT our LAN to a single IP rather then assign a
ton of external IPs for tech support workstations.

I tend not to run unwanted or extra services so OMG they get a TCP Reset
packet out of me!

--Dan

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