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Do ICMP re-directs actually work ?
From: "Naveed Anwar" <naveed () middleoffice com>
Date: Tue, 30 Oct 02:56:24 2001 +0000


Hi All

I have just been conducting a test in one of our labs by sending ICMP
redirects to a Windows 2000 Advanced Server using ICMPUSH. Using a
sniffer I see the packet successfully leave my machine, then again
from the target box I see the re-direct arrive. Say for example my
target machine is called Pepsi, and I tell it to redirect any packets
for a machine called Fanta to a dead gateway, hence communication to
Fanta will fail for the lifetime of the redirect.

Now my understanding is that the target server (Pepsi) should now
have updated its local routing table with respect to the Fanta
machine. Then from Pepsi I try to ping/telnet/http/ftp etc..(i.e
establish communication) to Fanta I am able to. The point is since I
told Pepsi via a redirect to send all traffic for Fanta to a
blackhole, how is the communication working.

One interesting point is that when I issue a netstat -rn to view the
routing table, I see no route update from the ICMP redirect. 

After reading Ofir's excellent paper I understand most ICMP
implementations are OS specific, therefore I guess redirects do not
work in Win2000 or Linux 6.2 which I also tested..or am I doing
something horribly wrong?

Thanks
Naveed

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