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?"

    Relevant Pages

    • Re: tpg cancel attack
      ... Internet connections to move traffic. ... common set of communications protocols. ... The vast collection of inter-connected networks across the world that ... A worldwide network of computer networks. ...
      (talk.politics.guns)
    • Re: Steve our posts have been deleted!!!!!
      ... That's due to the amount of bandwidth used for streaming! ... internet to serve 10-million listeners; there is simply no way the ... actually where in the coverage-zone of their terrestial networks. ... Of course, when you are talking about non-linear broadcasting, that's ...
      (alt.radio.digital)
    • RE: GPO that forces users to use a proxy server.
      ... as I would think home networks are not proxied and filtered. ... GPO that forces users to use a proxy server. ... proxy sever for there internet access in the company, ...
      (Focus-Microsoft)
    • Should Obama Control the Internet?
      ... Do you know about the Rockefeller Snowe job? ... A new bill would give the President emergency authority to halt web ... Should President Obama have the power to shut down domestic Internet ... concerning networks without regard to any provision of law, ...
      (alt.gathering.rainbow)
    • RE: How hackers cause damage...
      ... PBX and phone systems are PUBLIC networks. ... than list the internet as an agreed path. ... The cost of security is inverse ... Network Vulnerability Assessment project here in Australia and you may ...
      (Security-Basics)