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RE: IP announce DOS
From: "Thomas Ng" <thomasng () ida gov sg>
Date: Fri, 10 Jun 2005 11:50:03 +0800


Shouldn't it be that each ISPs have their own big blocks? Chances are,
the class C given to you is in the middle of one of these huge blocks. I
am not sure what is your agreement with the old and new ISP, but I don't
think it is that simple to transfer the same set of IPs from one ISP to
another. It is technically possible ... but I don't think it is that

Usually what I do when I change ISP is to just ask for a new set of IPs
from the new ISP, change the DNS, allow the TTLs to run out and shift to
the new sets of IP address. If you play with the DNS correctly, you can
get minimal downtime, dependent on size and sophistication of your


-----Original Message-----
From: Alex Thurlow [mailto:buddychrist () gmail com]
Sent: Thursday, June 09, 2005 5:24 AM
To: 'security-basics () securityfocus com'
Subject: IP announce DOS
Importance: High

I'm not positive this is the correct list to ask, but it is a security
concern, so I thought I would.  The company I work for had T1 lines
running to our office provided by a local provider.  We had our own C
block of IPs being announced by them and routed to us over those T1s.
Our relationship with them went sour (for many reasons I won't get
here), and we had to move to a different provider.  We had the routing
switched over to them.  Everything was fine.  Here it is a few weeks
later, and suddenly our old provider starts announcing these IPs
The end result is a partial DOS attack (hence writing to this list) as
some people can't reach us.  They won't stop the announcement.  I
know all the details on what they've said there as it's now gone to
executives and legal people dealing with them.  Is there anything we
do here from a network standpoint?  Someone we can report them to?
do people protect themselves from just anyone announcing IPs that

Thanks in advance,
Alex Thurlow


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