Paul on Wed, 24 Sep 2003 13:14:12 -0400


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Re: [PLUG] Firewall Check


I'm far from confused about IPv4 networking. I'm only mildly concerned about ICMP because all other protocols have been filtered already. I like the idea of ignoring "icmp_echo_ignore_broadcasts". I just want my system to respond to legitimate pings from the Internet without being overly permissive to ICMP communications.


Ruse, Kevin KPSI wrote:

We'll i'm confused by that question as that would only limit icmp. I'm
thinking you may be slightly confused about ip networking.

You have three commonly used protocols running across IP ICMP, TCP, and
UDP. ICMP is the Internet Control Message Protocol and was intended for use
as an error control mechanism for IP. It is considered part of IP not an
application layer service running on top of it like a TCP (ssh) or UDP(dns)
service. Pings are part of the icmp protocol.

For those two commands below, the first tells the os to ignore all icmp
packets with an ICMP type of 8 (echo request ie ping) thet second is a
subset of that which tells it to ignore all icmp packets with an ICMP type
of 8 which were sent to the broadcast address.


Kevin Ruse
Kvaerner Philadelphia Shipyard


-----Original Message----- From: Paul [mailto:emailme@dpagin.net] Sent: Tuesday, September 23, 2003 7:08 PM To: plug@lists.phillylinux.org Subject: Re: [PLUG] Firewall Check


Ruse, Kevin KPSI wrote:



If you want to block pings, you can also do a

echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts





Very cool. I think, if anything, I would only limit ICMP. Hmm...how would I do that?


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_________________________________________________________________________
Philadelphia Linux Users Group -- http://www.phillylinux.org
Announcements - http://lists.netisland.net/mailman/listinfo/plug-announce
General Discussion -- http://lists.netisland.net/mailman/listinfo/plug




_________________________________________________________________________
Philadelphia Linux Users Group        --       http://www.phillylinux.org
Announcements - http://lists.netisland.net/mailman/listinfo/plug-announce
General Discussion  --   http://lists.netisland.net/mailman/listinfo/plug