Firewall Wizards mailing list archives
Re: ICMP Packets.
From: Bennett Todd <bet () rahul net>
Date: Tue, 2 Jun 1998 07:47:54 -0700
1998-06-01 Toddb:. . .Is there a list of ICMP message types that are needed as opposed to ones that are just used for troubleshooting (like echo, echo-reply) that can be blocked without problems.Forget the list . . . as it has been said by MANY that have said it before, if you don't need it, block it, both ways.
So he asked for the list of ICMP message types that _are_ needed, and gave an example ``packet-too-big'' (in part of the text you didn't quote). There are some ICMP packets that you do need to let in, lest path MTU discovery break (and maybe some other things?). I am also interested in the answer to this question: what ICMP packet types do you need to allow through the filters, to help ensure that other protocols work right? I'm rassling with this right now myself; I'm trying to craft up a set of ipfilter rules that are as utterly strict as possible; I'm hoping for a baseline bastion host config where everything is allowed out, but initially the only thing allowed in is port 22/tcp (ssh) on the inside interface only. I've basically got that right. But my current baseline isn't allowing in any ICMP at all, and I expect there are some subtle things that will break in the future if I don't relax that a bit, and I'd love to know exactly what I need to let in, and why. -Bennett
Current thread:
- ICMP Packets. Toddb (Jun 01)
- Re: ICMP Packets. Henry Hertz Hobbit (Jun 02)
- Re: ICMP Packets. Bennett Todd (Jun 02)
- Re: ICMP Packets. Perry E. Metzger (Jun 02)
- Re: ICMP Packets. tqbf (Jun 02)
- Re: ICMP Packets. Darren Reed (Jun 03)
- <Possible follow-ups>
- Re: ICMP Packets. Don Kendrick (Jun 02)
- Re: ICMP Packets. Perry E. Metzger (Jun 02)
- Re: ICMP Packets. Alec Muffett - SunLabs (Jun 02)
- Re: ICMP Packets. James R Grinter (Jun 02)
- Re: ICMP Packets. Henry Hertz Hobbit (Jun 03)
- Re: ICMP Packets. Don Kendrick (Jun 02)
- Re: ICMP Packets. Perry E. Metzger (Jun 02)
(Thread continues...)
- Re: ICMP Packets. Henry Hertz Hobbit (Jun 02)