[ntp:questions] configurations issue for broadcastclient in Linux machine

Danny Mayer mayer at ntp.isc.org
Tue May 15 02:57:57 UTC 2007


Ravikiran REDDY -X (ravikred - HCL at Cisco) wrote:
>  Hello,
> 
> Please clarify,
> Linux machine when configured as broadcast client is not able to create
> associations for the pkts received from the server [cisco router]
> Am I missing anything here or should I need to have any additional
> configuration in the ntp.conf file ? 
>   
> Server 	  	=>  cisco router with ntp image [ ip address 9.9.4.13 ]
> Linux machine 	=>  broadcast client [ ip address 9.9.4.16 ]
> 			    [root at nsstg-ntp-lnx ntpv4]# uname -a
> 			    Linux nsstg-ntp-lnx 2.4.20-8 #1 Thu Mar 13
> 17:54:28 EST 2003 i686 i686 i386 GNU/Linux
> 	     		    [root at nsstg-ntp-lnx ntpv4]# 
> NTP version  	=>  ntpq> version
> 		          ntpq 4.2.2p4 at 1.1585-o Fri May 11 01:34:46 UTC
> 2007 (1)
> 			    ntpq>
> 
> --------ntp.conf file -----
> broadcastclient
> driftfile /etc/ntp/drift
> ----------------------------
> 
> 
> ----------- snippet from tcpdump on the Linux machine --------
> 00:58:55.882919 9.9.4.13.ntp > 255.255.255.255.ntp:  v4 bcast strat 8

Do you know why it's insisting on sending the packet out to the
255.255.255.255 IP Address?

Have you seen bug #629? https://ntp.isc.org/bugs/show_bug.cgi?id=629

The problem is that cisco seems to use the all broadcast address. I have
discussed this with someone inside cisco but it looks like I will have
to create a case for this situation. If I do so, you cannot do
authentication on the received packets so you use at your own risk. This
is because the packet gets received on the wildcard socket rather than
the socket assigned for the purpose of receiving broadcast packets. We
don't recommend this and I'm going to have to add configuration options
to the config file to specify how to deal with this sort of thing.

Danny




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