Re: two hosts with the same IP
Sten Carlsen <[email protected]> Thu, 11 Jul 2024 12:11:51 +0200
| Newsgroups | gmane.network.dhcp.isc.dhcp-server |
|---|---|
| Message-ID | <[email protected]> |
--===============7083231458391879708== Content-Type: multipart/alternative; boundary=Apple-Mail-8FE4E394-6AEE-408E-ADC6-4478FC2AECCD Content-Transfer-Encoding: 7bit --Apple-Mail-8FE4E394-6AEE-408E-ADC6-4478FC2AECCD Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable <html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D= utf-8"></head><body dir=3D"auto">I believe there should be a specific warnin= g in the log during startup.<br id=3D"lineBreakAtBeginningOfSignature"><div d= ir=3D"ltr"><pre class=3D"moz-signature" cols=3D"72"><font face=3D".SFUIDispl= ay-Regular"><span style=3D"white-space: normal; background-color: rgba(255, 2= 55, 255, 0);">--=20 Best regards</span></font></pre><pre class=3D"moz-signature" cols=3D"72"><fo= nt face=3D".SFUIDisplay-Regular"><span style=3D"white-space: normal; backgro= und-color: rgba(255, 255, 255, 0);">Sten Carlsen</span></font></pre><pre cla= ss=3D"moz-signature" cols=3D"72"><font face=3D".SFUIDisplay-Regular"><span s= tyle=3D"white-space: normal; background-color: rgba(255, 255, 255, 0);">No i= mprovements come from shouting:</span></font></pre><pre class=3D"moz-signatu= re" cols=3D"72"><font face=3D".SFUIDisplay-Regular"><span style=3D"white-spa= ce: normal; background-color: rgba(255, 255, 255, 0);">"MALE BOVINE MANURE!!= !" </span></font></pre></div><div dir=3D"ltr"><br><blockquote type=3D"cite">= On 11 Jul 2024, at 02.23, Glenn Satchell <[email protected]> w= rote:<br><br></blockquote></div><blockquote type=3D"cite"><div dir=3D"ltr">=EF= =BB=BF<div dir=3D"auto"><div dir=3D"auto"><div>hi Brian,</div><div dir=3D"au= to"><br></div><div dir=3D"auto">fixed-address assignments must be outside th= e pool of dynamic addresses to prevent this situation.</div><div dir=3D"auto= "><br></div><div dir=3D"auto">If the fixed-address device is down, then the d= ynamic pool will see that as free when it does a ping check and happily assi= gn it. then when the fixed-address device requests the ip it will always be a= ssigned.</div><div><br></div><div dir=3D"auto">This is mentioned in the docs= , dhcpd.conf man page i think.</div><div dir=3D"auto"><br></div><div data-sm= artmail=3D"gmail_signature">regards,<br>Glenn</div></div><div><br><div class= =3D"elided-text">On 11 July 2024 6:12=E2=80=AFam, "Cuttler, Brian R (HEALTH)= " <[email protected]> wrote:<br type=3D"attribution"><blockq= uote style=3D"margin:0 0 0 0.8ex;border-left:1px #ccc solid;padding-left:1ex= "><div style=3D"word-wrap:break-word"> <div> <p>Running DHCP on Ubuntu 22.04.4 LTS</p> <p> </p> <p>brian@cedar:/var/log$ DHCP -V</p> <p>Internet Systems Consortium DHCP Server 4.4.1</p> <p>Copyright 2004-2018 Internet Systems Consortium.</p> <p> </p> <p>Noted one system in particular was having network issues, ping to t= he IP was good, ping from the IP was problematic, lots of dropping pings in a= bout 25 second groups/blocks.</p> <p> </p> <p>Also having trouble maintaining SSH connection into the host, and host ke= ys needed to be removed and reaccepted.</p> <p> </p> <p>On a hunch I checked the dhcp log and found two different MAC addresses r= eceiving the same IP.</p> <p> </p> <p>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</p> <p>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</p> <p>Jul 10 15:04:17 cedar DHCP[1019]: DHCPREQUEST for 10.50.148.212 from b0:7= b:25:de:57:84 (berkeley) via 10.50.148.1</p> <p>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</p> <p>Jul 10 15:05:16 cedar DHCP[1019]: DHCPDISCOVER from b0:7b:25:de:57:84 (be= rkeley) via 10.50.148.1</p> <p>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</p> <p>Jul 10 15:05:16 cedar DHCP[1019]: DHCPREQUEST for 10.50.148.212 (10.50.15= 6.21) from b0:7b:25:de:57:84 (berkeley) via 10.50.148.1</p> <p>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</p> <p> </p> <p>I also note that one of the two hosts has a reservation.</p> <p> </p> <p> host Suraj {<!-- --></p> <p> &= nbsp; hardware ethernet d4:5d:64:08:91:7c;</p> <p> &= nbsp; fixed-address 10.50.148.212;</p> <p> &= nbsp; }</p> <p> </p> <p>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=E2=80=99m very surp= rised by the behavior we were seeing.<br> If the non-received MAC received the IP wouldn=E2=80=99t the MAC with the re= servation still cause a ping test for availability to be performed?<br> I can=E2=80=99t think of any other way this could have happened.</p> <p> </p> <p>Can anyone help me to understand what actually happened and how best to p= revent similar events in the future?<br> <br> thanks in advance,</p> <p>Brian</p> <p> </p> <p> </p> <p><span style=3D"font-size:12pt;font-family:'arial' , serif">Brian Cuttler,= System and Network Administration</span></p> <p><span style=3D"font-size:12pt;font-family:'arial' , serif">Wadsworth Cent= er, NYS Department of Health</span></p> <p><span style=3D"font-size:12pt;font-family:'arial' , serif">Albany, NY 122= 01 POB 509</span></p> <p><span style=3D"font-size:12pt;font-family:'arial' , serif"><a href=3D"mai= lto:[email protected]"><span style=3D"color:#0563c1">Brian.Cuttler= @Health.NY.gov</span></a></span></p> <p><span style=3D"font-size:12pt;font-family:'arial' , serif">518 486-1697</= span><span style=3D"font-size:12pt;font-family:'arial nova' , sans-serif"></= span></p> <p> </p> </div> </div> </blockquote></div><br></div></div><span>-- </span><br><span>ISC funds the d= evelopment of this software with paid support subscriptions. Contact us at h= ttps://www.isc.org/contact/ for more information.</span><br><span></span><br= ><span>dhcp-users mailing list</span><br><span>[email protected]</spa= n><br><span>https://lists.isc.org/mailman/listinfo/dhcp-users</span><br></di= v></blockquote></body></html>= --Apple-Mail-8FE4E394-6AEE-408E-ADC6-4478FC2AECCD-- --===============7083231458391879708== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline -- ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information. dhcp-users mailing list [email protected] https://lists.isc.org/mailman/listinfo/dhcp-users --===============7083231458391879708==--