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Old 11-06-2004, 02:43 AM   #1
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UDP packets dont seem to go out!

I have a HP Proliant server with an NetXtreme BCM 5702 Gigabit Ethernet Adaptor. The machine is running Redhat Linux ES with kernel 2.4.21. On this machine is a program which sends out a broadcast every 20 seconds. For some wierd reason, the data is not getting to the network. I can see it on the local machine but not on any other client. Ethereal couldnt see it. Am i missing something?
Old 11-06-2004, 11:30 AM   #2
Registered: Jul 2004
Location: USA
Distribution: Slackware, FreeBSD, LFS
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It may be your firewall is dropping them. Are you able to use any other
UDP services? DNS usually uses UDP, so if your web is working that's
a yes. You may want to try to add an iptables rule to test if it's your firewall.
There's a variety of rules you could use. You could use a rule specifying
whatever broadcast address your using. This rule assumes its

#iptables -I OUTPUT 1 -d -j ACCEPT

Or you could use a rule to allow that program to communicate however it wants.
I don't know the name of your program, but here is an example using traceroute.

#iptables -I OUTPUT 1 -m owner --cmd-owner traceroute -j ACCEPT

If any rules like that allow you to see this traffic elsewhere on the network, or
through ethereal, go ahead and add them to your startup firewall. You may
want to add INPUT rules to allow any needed traffic coming in as well.
Old 11-06-2004, 10:55 PM   #3
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iptables,ip6tables,firewall or ipsec are not enabled. all these services are disabled. Moreover, after the program is initialised, Nmap reveals none of the specified ports as open. How could that be!?

Last edited by linuxspartan; 11-07-2004 at 11:23 AM.


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