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To subscribe or unsubscribe via the World Wide Web, visit https://lists.isc.org/mailman/listinfo/dhcp-users or, via email, send a message with subject or body 'help' to dhcp-users-requ...@lists.isc.org You can reach the person managing the list at dhcp-users-ow...@lists.isc.org When replying, please edit your Subject line so it is more specific than "Re: Contents of dhcp-users digest..." Today's Topics: 1. Re: isc dhcp server weird hostname option value (Bill Shirley) ---------------------------------------------------------------------- Message: 1 Date: Fri, 23 Jun 2017 10:23:04 -0400 From: Bill Shirley <b...@c3po.polymerindustries.biz> To: dhcp-users@lists.isc.org Subject: Re: isc dhcp server weird hostname option value Message-ID: <32000ed4-760e-34ff-61f3-adda97251...@c3po.polymerindustries.biz> Content-Type: text/plain; charset="utf-8"; Format="flowed" I have a some devices that don't provide a hostname. Dynamic DNS doesn't get updated without a hostname. I use: # ------------------------------------------------------------------------------ class "NoName" { match if not ( exists server.ddns-hostname or exists fqdn.hostname or exists host-name ); ddns-hostname = concat("NoName-", binary-to-ascii(16, 8, "", substring(hardware, 4, 3))); option dhcp.host-name = config-option server.ddns-hostname; # option fqdn.hostname = config-option server.ddns-hostname; } # ------------------------------------------------------------------------------ to create a hostname for them. It uses the last 3 bytes of the MAC address as part of the host name. Note: I'm using 'option dhcp.host-name' instead of 'option host-name'. I really don't know if that matters. You might also try 'option fqdn.hostname'. You can even confine them to a pool: pool { deny dynamic bootp clients; allow members of "NoName"; . . } HTH, Bill On 6/23/2017 7:28 AM, Radoslav Pe?ek wrote: > > Hi all, > > I sent this email few weeks ago (without being subscribed here), and didn't > receive any reply, nor do I see it in lists > archive. So I write once again after subscription, hope it will work now. > > ~~~~ > > My isc dhcp server behaves strangely - it sends some clients dhcp hostname > option value which I don't know where it is getting > it from. > > It's on Debian 8.5, version 4.3.1. It's in failover mode. > > I'm using dynamic hostname generation for some clients based on last byte of > their mac address: > > |set mac_6 = suffix(concat("0", binary-to-ascii(16, 8, "", > substring(hardware, 6, 1))), 2); ddns-hostname = concat("vm1", > mac_6); option host-name = config-option server.ddns-hostname; | > > So for example client with mac address ending 02 should get hostname vm102 - > and it seems to work correctly - I added logging > to my dhcp config and I see in log file both option host-name and > config-option server.ddns-hostname set to vm102. > > I also see in dhcpd.leases > > |set mac_6 = "02"; client-hostname "vm102"; | > > But when I run tcpdump for this client, I see > > |Hostname Option 12, length 5: "vm121" | > > and at least once it changed to vm103. > > So where is it getting it from? What are the sources for this option when > dhcp server sends DHCPOFFER or DHCPACK? > > It works after dhcp server restart, but then it starts again after a whlie. > > I tried to read isc-dhcp-server's source code but got bit lost as it was hard > to follow. > > Thanks for any help. > > Rado. > > > > > _______________________________________________ > dhcp-users mailing list > dhcp-users@lists.isc.org > https://lists.isc.org/mailman/listinfo/dhcp-users -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://lists.isc.org/pipermail/dhcp-users/attachments/20170623/ccc53265/attachment-0001.html> ------------------------------ Subject: Digest Footer _______________________________________________ dhcp-users mailing list dhcp-users@lists.isc.org https://lists.isc.org/mailman/listinfo/dhcp-users ------------------------------ End of dhcp-users Digest, Vol 104, Issue 11 *******************************************