What could this icmp mean?

From: Tomas (s.tomas_at_gmail.com)
Date: 02/22/05

  • Next message: David Gillett: "RE: What could this icmp mean?" 
    To: <security-basics@securityfocus.com>
Date: Tue, 22 Feb 2005 15:11:27 +0200

    Hello list,

    We have networks (10.30.0.0/24 and 10.30.1.0/24) connected trough VPN and
    one internet line. The gateways for VPN are 10.30.0.1 from one side and
    10.30.1.1 from the other, and 10.30.1.254 for internet (for both networks).

    I've launched tcpdump today on my internet firewall's internal interface
    (10.30.1.254) and I found this:

    10.30.1.254 > 10.30.1.16: icmp: redirect 10.30.0.4 to host 10.30.1.1 for
    10.30.1.16.445 > 10.30.0.4.1959: [|tcp] (DF) (ttl 127, id 7691, bad cksum
    c76d! differs by 100) (ttl 255, id 23807)

    I'm a bit confused, what could this icmp mean? First of all, I'm sure that
    neither of these hosts (10.30.1.254, 10.30.1.16, 10.30.0.4) are sending any
    icmp requests (I'm not sure about 10.30.1.1; it's not in my control). And
    the second of all, why the checksum is bad?

  • Next message: David Gillett: "RE: What could this icmp mean?"

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