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<p class="MsoNormal">Running DHCP on Ubuntu 22.04.4 LTS<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">brian@cedar:/var/log$ DHCP -V<o:p></o:p></p>
<p class="MsoNormal">Internet Systems Consortium DHCP Server 4.4.1<o:p></o:p></p>
<p class="MsoNormal">Copyright 2004-2018 Internet Systems Consortium.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Noted one system in particular was having network issues, ping to the IP was good, ping from the IP was problematic, lots of dropping pings in about 25 second groups/blocks.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Also having trouble maintaining SSH connection into the host, and host keys needed to be removed and reaccepted.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">On a hunch I checked the dhcp log and found two different MAC addresses receiving the same IP.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Jul 9 11:49:38 cedar DHCP[1019]: DHCPREQUEST for 10.50.148.212 from d4:5d:64:08:91:7c via 10.50.148.1<o:p></o:p></p>
<p class="MsoNormal">Jul 9 11:49:38 cedar DHCP[1019]: DHCPACK on 10.50.148.212 to d4:5d:64:08:91:7c via 10.50.148.1<o:p></o:p></p>
<p class="MsoNormal">Jul 10 15:04:17 cedar DHCP[1019]: DHCPREQUEST for 10.50.148.212 from b0:7b:25:de:57:84 (berkeley) via 10.50.148.1<o:p></o:p></p>
<p class="MsoNormal">Jul 10 15:04:17 cedar DHCP[1019]: DHCPACK on 10.50.148.212 to b0:7b:25:de:57:84 (berkeley) via 10.50.148.1<o:p></o:p></p>
<p class="MsoNormal">Jul 10 15:05:16 cedar DHCP[1019]: DHCPDISCOVER from b0:7b:25:de:57:84 (berkeley) via 10.50.148.1<o:p></o:p></p>
<p class="MsoNormal">Jul 10 15:05:16 cedar DHCP[1019]: DHCPOFFER on 10.50.148.212 to b0:7b:25:de:57:84 (berkeley) via 10.50.148.1<o:p></o:p></p>
<p class="MsoNormal">Jul 10 15:05:16 cedar DHCP[1019]: DHCPREQUEST for 10.50.148.212 (10.50.156.21) from b0:7b:25:de:57:84 (berkeley) via 10.50.148.1<o:p></o:p></p>
<p class="MsoNormal">Jul 10 15:05:16 cedar DHCP[1019]: DHCPACK on 10.50.148.212 to b0:7b:25:de:57:84 (berkeley) via 10.50.148.1<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I also note that one of the two hosts has a reservation.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> host Suraj {<o:p></o:p></p>
<p class="MsoNormal"> hardware ethernet d4:5d:64:08:91:7c;<o:p></o:p></p>
<p class="MsoNormal"> fixed-address 10.50.148.212;<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">While I realize that a host with a reservation might be down, and another machine could get the IP if its in the available pool I’m very surprised by the behavior we were seeing.<br>
If the non-received MAC received the IP wouldn’t the MAC with the reservation still cause a ping test for availability to be performed?<br>
I can’t think of any other way this could have happened.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Can anyone help me to understand what actually happened and how best to prevent similar events in the future?<br>
<br>
thanks in advance,<o:p></o:p></p>
<p class="MsoNormal">Brian<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",serif;mso-ligatures:none">Brian Cuttler, System and Network Administration<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",serif;mso-ligatures:none">Wadsworth Center, NYS Department of Health<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",serif;mso-ligatures:none">Albany, NY 12201 POB 509<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",serif;mso-ligatures:none"><a href="mailto:Brian.Cuttler@Health.NY.gov"><span style="color:#0563C1">Brian.Cuttler@Health.NY.gov</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",serif;mso-ligatures:none">518 486-1697</span><span style="font-size:12.0pt;font-family:"Arial Nova",sans-serif;mso-ligatures:none"><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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