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December 2003, Week 3

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Subject:
Re: FTP failing to connect.
From:
Jeff Kell <[log in to unmask]>
Reply To:
Jeff Kell <[log in to unmask]>
Date:
Mon, 15 Dec 2003 13:08:05 -0500
Content-Type:
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text/plain (21 lines) 
Alan Yeo wrote:

> It may well be your ISP, or in fact BT in the UK. I had a similar
> problem with Ping and Traceroute about a month back. When I spoke to the
> ISP where this wasn't working, I was told that they and BT were blocking
> the packages that Ping and Traceroute use, because of all the virus
> traffic.

Nachi/Welchia generate pings with an IP length of 92 and a 64-byte
payload of all 0xAA's.  Many ISPs are blocking matching pings (as are
we) to avoid the garbage traffic.  A Cisco can match on the packet type
and packet length and drop it in hardware.  But it can't inexpensively
check the packet payload.

Now guess what characterizes a Windows TRACERT.  :-)

Jeff

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