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20030910: blocked ICMP packets

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  • Subject: 20030910: blocked ICMP packets
  • Date: Wed, 10 Sep 2003 08:57:07 -0600
>From: Ruth Platner <address@hidden>
>Organization: URI
>Keywords: 200309101422.h8AEMoLd015137

Ruth,

>The network technicians at our university have blocked ICMP packets from
>going through our router. This was in response to erratic router
>behavior, possibly caused by ICMP flooding by the Welchia worm. I
>thought this would be temporary, but it seems to be a permanent
>situation.

>This has resulted in ping and traceroute not being able to get beyond
>the blocked router. Because traceroute doesn't work, netcheck, which
>uses traceroute, reports 100% packet loss every hour to our upstream
>data site.

You should be able to use 'ldmping' to gather information about whether
your upstream site is up or not.  'ldmping', like other LDM programs
uses port 388 for communication.

>Aside from netcheck, is there any other part of the ldm that would be
>affected by traceroute being nonfunctional?

No.  I would pay attention to any sort of blocking/rate limiting that
might be done that would affect port 388 traffic, however.  A number of
schools' networking groups are installing packet shaping software to
control the use of their networks.  The best way to insure good IDD
connectivity is to work with your network folks to allow unimpeded port
388 traffic.  Our experience is that the networking groups are usually
very reptive to opening wide port 388 after they are made aware of its
strategic use for research and educational data flows.

>Thanks for your help,

No worries.

Tom Yoksas