Re: UDP port not listening..

From: Joe Loiacono (
Date: Thu Jul 05 2001 - 11:16:43 PDT

  • Next message: Martin van den Nieuwelaar: "Re: UDP port not listening.. tips on what to check for and how to check"


    I'm currently battling this with one of my new installations. First, the
    collector listens to the routers on port 2055, it communicates with cflowd
    on port 2056 (both are defaults.) So you should be doing tcpdump looking
    for port 2055 (not 2255, unless you've changed it from the default.) Using
    netstat, UDP port 2055 should be listed, but probably in idle. Also, it may
    be the case that a firewall somewhere between the router and your collector
    is dropping your packets.


    At 07:54 AM 07/05/2001 -0700, you wrote:
    >I would like to ask the help of people who have cflowd up and running
    >on thier boxes and are
    >receiving flows. I have install cflowd on a PIII 450 RH Linux 7.1 box
    >with 256MB and have yet to
    >receive flows even though I am currently getting no error messages.
    >Whenever I do a tcp dump The
    >only communication that I see between my routers (7507, 6509 w/ msfc)
    >and my collecter are snmp
    >requests and responses. However I was told that if I run 'tcpdump -n
    >udp port 2255' (2056 is the
    >port that I am using to recieve upd flows) i should see something
    >similar to this:
    >collector# tcpdump -n udp port 2255
    >tcpdump: listening on all devices
    >12:11:29.953100 > udp 1168
    >12:11:29.965310 > udp 1168
    >12:11:29.967780 > udp 1168
    >12:11:29.985854 > udp 1168
    >12:11:29.998673 > udp 1168
    >12:11:29.009464 > udp 1168
    >but I do not.
    >When I do 'netstat -an' the tcp port is listening but not the udp port.
    >Is this regular or is
    >there a problem here? Any help is appreciated.
    >Edson Manners
    >Academic Computing & Networking Services
    >Florida State University
    >Do You Yahoo!?
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    >cflowd mailing list

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