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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Use this command:-<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>dhcrelay –d –i eth0 192.168.9.2<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>ensure that from </span><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>80.1.1.1/24 your DHCP-Server is reachable (vice versa). <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>Arun.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> arunprasad [mailto:arunprasad@pointred.co] <br><b>Sent:</b> Wednesday, April 18, 2012 10:05 PM<br><b>To:</b> 'Users of ISC DHCP'<br><b>Subject:</b> RE: DHCP Relay: Duplicate packets for DHCPRELEASE and DHCPREQUEST<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>Hi Sujata,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>dhcrelay -d -i eth0 -i eth1 serverip <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>-i ifname <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>Listen for DHCPv4/BOOTP queries on interface ifname. Multiple interfaces may be specified by using more than one -i option. If no interfaces are specified on the command line, dhcrelay will identify all network interfaces, eliminating non-broadcast interfaces if possible, and attempt to listen on all of them. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>So try running dhrelay on your downstream interface only i.e.. 80.1.1.1/24 interface.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>PS:- IP Forwarding needs to enable. If your setup is as below.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>Windows 2003 server ( 192.168.9.2/23)-------------------(192.168.8.177/23) Linux PC(Relay) (80.1.1.1/24----------eth0----Windows XP Client ( DHCP client getting IP 80.1.1.2/24) <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Cambria","serif";color:#376092'>Arun.<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> dhcp-users-bounces+arunprasad=pointred.co@lists.isc.org [mailto:dhcp-users-bounces+arunprasad=pointred.co@lists.isc.org] <b>On Behalf Of </b>Sujata Verma<br><b>Sent:</b> Wednesday, April 18, 2012 6:36 PM<br><b>To:</b> Users of ISC DHCP<br><b>Subject:</b> Re: DHCP Relay: Duplicate packets for DHCPRELEASE and DHCPREQUEST<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td valign=top style='padding:0in 0in 0in 0in'><p class=MsoNormal><br>Thanks for the reply. <br><br>Yes, it is duplicating the unicast DHCPREQUEST packets as well. <br><br>So is it a bug, is there anything i can do to stop doing it ( in code ) , any pointers? <br><br>@Arun,<br><br>There is no switch in between, the setup to be precise is <br><br><br>Win Server-----------cross cable--------------Linux PC------------hub-------Win XP client<br>192.168.9.1/24 192.168.9.2/24 10.1.1.2/8 10.1.1.3/8 ( from server)<br><br>I changed the subnet as above but same behavior.<br><br><br>One more observation : <br><br>if i disable ip_forward flag , the DHCP relay agent is sending only one DHCPRELEASE packet with correct giaddr ( incoming eth0 interface ). But as forwarding is disabled it is understood that the client DHCPRELEASE message is not forwarded to the server but why the other "eth1" interface DHCPRELEASE message is not being generated from relay agent? <br><br>Any pointers? <br><br>Regards,<br>Sujata<br><br><br><br><br>--- On <b>Wed, 4/18/12, Simon Hobson <i><<a href="mailto:dhcp1@thehobsons.co.uk">dhcp1@thehobsons.co.uk</a>></i></b> wrote:<o:p></o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'><br>From: Simon Hobson <<a href="mailto:dhcp1@thehobsons.co.uk">dhcp1@thehobsons.co.uk</a>><br>Subject: Re: DHCP Relay: Duplicate packets for DHCPRELEASE and DHCPREQUEST<br>To: "Users of ISC DHCP" <<a href="mailto:dhcp-users@lists.isc.org">dhcp-users@lists.isc.org</a>><br>Date: Wednesday, April 18, 2012, 5:21 PM<o:p></o:p></p><div><p class=MsoNormal>Sujata Verma wrote:<br><br>> My setup is like this : eth1<br>> Windows 2003 server ( 192.168.9.2/23)-------------------(192.168.8.177/23) Linux PC(Relay) (80.1.1.1/24----------eth0----Windows XP Client ( DHCP client getting IP 80.1.1.2/24)<br><br>That's better<br><br>> I am attaching the wireshark capture for both client and server. In this we can see that the DHCPDISCOVER is only being sent once to the server which relay is forwarding while adding giaddr field as 80.1.1.1 .<br>> <br>> When DHCPRELEASE packet is being sent, it is sent directly to the server and with other two packets as duplicates with giaddr as of two interfaces.<br><br>My guess (I've not actually used the ISC relay) is that it's sniffing the packets and picking up the unicast packet from the client to the server both when it enters the relay on eth0 and when it exits via eth1. That, to my understanding, is wrong.<br><br>It would be interesting to see what happens to a unicast DHCP-Request packet ? The Request packet in your captures is a broadcast packet which is being relayed by the Relay Agent (correctly). You will need to (temporarily) tweak your server config down to a short lease time so that the client will renew in a timescale that's workable.<br>Based on the above, I suspect you'll see those packets duplicated as well.<br><br>-- Simon Hobson<br><br>Visit <a href="http://www.magpiesnestpublishing.co.uk/" target="_blank">http://www.magpiesnestpublishing.co.uk/</a> for books by acclaimed<br>author Gladys Hobson. Novels - poetry - short stories - ideal as<br>Christmas stocking fillers. Some available as e-books.<br>_______________________________________________<br>dhcp-users mailing list<br><a href="/mc/compose?to=dhcp-users@lists.isc.org">dhcp-users@lists.isc.org</a><br><a href="https://lists.isc.org/mailman/listinfo/dhcp-users" target="_blank">https://lists.isc.org/mailman/listinfo/dhcp-users</a><o:p></o:p></p></div></td></tr></table><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p></div></body></html>
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