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</o:shapelayout></xml><![endif]--></head><body lang=EN-AU link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Yeah that definitely looks like a kernel bug or software bug with the network apps, check for an update, if you can’t find one I would log a bug with centos / RHEL themselves and allow them to escalate it upstream, be prepared to provide a LOT of information though as part of the bug process </span><span style='font-size:11.0pt;font-family:Wingdings;color:#1F497D'>J</span><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><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thanks,<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-family:"Arial","sans-serif";color:#333333'>Ayden Beeson</span></b><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 lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> AusNOG [mailto:ausnog-bounces@lists.ausnog.net] <b>On Behalf Of </b>Joshua D'Alton<br><b>Sent:</b> Tuesday, 8 April 2014 2:12 PM<br><b>To:</b> Shannon Gernyi<br><b>Cc:</b> ausnog@lists.ausnog.net<br><b>Subject:</b> Re: [AusNOG] Strange broadcast behaviour on linux 2.6.32 - riddle me this<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Saw similar on an install of Centos 6.4, just figured it was the datacenters rolled version, as it went away when I booted into the OpenVZ kernel I installed on the server. Never saw it again after that.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p><div><p class=MsoNormal>On Tue, Apr 8, 2014 at 2:32 PM, Shannon Gernyi <<a href="mailto:shannon.gernyi@xsv.com.au" target="_blank">shannon.gernyi@xsv.com.au</a>> wrote:<o:p></o:p></p><p class=MsoNormal>Hey all,<br><br>I have a few boxen running CentOS 6.5 in a very vanilla install.<br><br>I ran into some weird behaviour that I couldn't get to the bottom of, and whilst a reboot "fixed" it, I'm not going to be able to sleep at night without asking the question, so riddle me this:<br><br>Box A is on a private network:<br><br>eth0 <a href="http://172.27.3.111/24" target="_blank">172.27.3.111/24</a><br><br>I'm have a requirement to broadcast on eth0, however, the box isn't sending said broadcast packets to the ethernet broadcast mac - it's sending out ARP requests for 172.27.3.255 instead.<br><br>12:49:44.129501 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:45.129494 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:46.129494 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:48.132491 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:49.132488 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:50.132491 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:52.135503 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:53.135486 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:54.135513 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:56.139497 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:57.139491 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:49:58.139494 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:50:00.131503 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:50:01.131490 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:50:02.131495 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:50:04.134495 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:50:05.134487 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:50:06.134490 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:50:08.137499 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:50:09.137488 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br><br>eth0 is definitely configured correctly regarding network/mask:<br><br>eth0 Link encap:Ethernet HWaddr REMOVED<br> inet addr:172.27.3.111 Bcast:172.27.3.255 Mask:255.255.255.0<br> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1<br> RX packets:227898706 errors:0 dropped:0 overruns:0 frame:0<br> TX packets:219816363 errors:0 dropped:0 overruns:0 carrier:0<br> collisions:0 txqueuelen:1000<br> RX bytes:59578359175 (55.4 GiB) TX bytes:145429518480 (135.4 GiB)<br> Interrupt:245<br><br>arp output confirms the above dump:<br><br>arp -n<br>Address HWtype HWaddress Flags Mask Iface<br>172.27.3.255 (incomplete) eth0<br><br><br>And finally, manually adding the IP to the arp table with a destination of ethernet broadcast (ie, where the frames should be directed anyway) made things work:<br><br>arp -s 172.27.3.255 ff:ff:ff:ff:ff:ff<br><br><br>12:56:30.232505 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:56:31.232506 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:56:32.232496 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:56:34.235510 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:56:35.235505 ARP, Request who-has 172.27.3.255 tell 172.27.3.111, length 28<br>12:56:36.042743 IP 172.27.3.111.53957 > 172.27.3.255.ha-cluster: UDP, length 225<br>12:56:36.236321 IP 172.27.3.111.53957 > 172.27.3.255.ha-cluster: UDP, length 246<br>12:56:36.236353 IP 172.27.3.111.53957 > 172.27.3.255.ha-cluster: UDP, length 225<br>12:56:38.238098 IP 172.27.3.111.53957 > 172.27.3.255.ha-cluster: UDP, length 225<br><br><br>Now, I can't go back and debug further, but if anyone has seen this or similar behaviour before - please share possible explanations. It's doing my head in!<br>_______________________________________________<br>AusNOG mailing list<br><a href="mailto:AusNOG@lists.ausnog.net">AusNOG@lists.ausnog.net</a><br><a href="http://lists.ausnog.net/mailman/listinfo/ausnog" target="_blank">http://lists.ausnog.net/mailman/listinfo/ausnog</a><o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p></div></div>
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