winders does use udp instead of icmp in their tracert program, IIRC (or at least they used to). At the risk of getting my head blown off, could we say that was foresight :) Eric
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Stephen J. Wilcox Sent: Monday, September 29, 2003 1:54 PM To: CA Windon Cc: nanog@merit.edu Subject: Re: ICMP Blocking Woes
Hmm noticed what I was to say has already been said, but to reiterate, if your provider is blocking ICMP other than echo/echoreply .. in this case ICMP unreachables and presumably fragments and other fundementally required icmps they are seriously broken and I would insist they fix it or else you move away
You didnt clarify that in your mail tho, is it the icmp unreachables that you arent getting or is your monitoring sending out icmp echos which are being filtering?
if its the latter then you can easily workaround by modifying your monitoring systems to use udp/tcp based probes which are probably better these days than sending icmp across third party networks anyhow
Steve
On Mon, 29 Sep 2003, CA Windon wrote:
Dear NANOG-ers,
I work for an information security company that is dependant upon ICMP for network mapping purposes (read: traceroute). On or about August 18, we were told, our upstream provider began blocking ICMP packets at its border in the Chicago NAP in an effort to cut down on the propagation of 'MSBlast'. This has effected our ability to accurately map our customers networks.
We've been in contact with an engineer in this provider's NOC who is either unable or unwilling to remove this ACL for our block of IPs.
Currently, we've been given two options. (1) Deal with the effect of the ACL until 'MSBlast' traffic subsides, or (2) they are willing to reroute our traffic out of the Chicago NAP to a border router that, they claim, does not have the same ACL. The problem with option 2 is that they would force us to renumber. This is a problem for us, as it would impact our customers as well.
What options can I take to my management that would cause the least impact to the services we provide while not causing undue work for our clients. Also, what other options could I suggest to my upstream provider?
TIA,
C. Windon
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