Public bug reported: I had a device request an IP on one VLAN (one interface associated with the server -- ens256), and then I moved the device to a different VLAN (interface ens192 on the server), and was surprised when the DHCPD process continued to hand out the same IP on the new VLAN.
Here are the associated syslog entries, and the IP interface settings: Jan 28 12:06:35 backup dhcpd[1020678]: DHCPREQUEST for 10.2.195.100 from ec:02:73:b8:4d:01 via ens256 Jan 28 12:06:35 backup dhcpd[1020678]: DHCPACK on 10.2.195.100 to ec:02:73:b8:4d:01 via ens256 Jan 28 12:08:43 backup dhcpd[1020678]: DHCPREQUEST for 10.2.195.100 from ec:02:73:b8:4d:01 via ens256 Jan 28 12:08:43 backup dhcpd[1020678]: DHCPACK on 10.2.195.100 to ec:02:73:b8:4d:01 via ens256 Jan 28 12:11:08 backup dhcpd[1024746]: DHCPREQUEST for 10.2.195.100 from ec:02:73:b8:4d:01 via ens192 Jan 28 12:11:08 backup dhcpd[1024746]: DHCPACK on 10.2.195.100 to ec:02:73:b8:4d:01 via ens192 Jan 28 12:11:23 backup dhcpd[1024746]: DHCPREQUEST for 10.2.195.100 from ec:02:73:b8:4d:01 via ens192 Jan 28 12:11:23 backup dhcpd[1024746]: DHCPACK on 10.2.195.100 to ec:02:73:b8:4d:01 via ens192 (I've trimmed out the IPv6 information): backup$ ip addr list ... 3: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000 link/ether 00:50:56:9e:8b:d8 brd ff:ff:ff:ff:ff:ff inet 10.7.32.2/21 brd 10.7.39.255 scope global ens192 valid_lft forever preferred_lft forever ... 5: ens256: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000 link/ether 00:50:56:9e:f2:e6 brd ff:ff:ff:ff:ff:ff inet 10.2.195.2/24 brd 10.2.195.255 scope global ens256 valid_lft forever preferred_lft forever ... When I rebooted the client, it went back to DHCPDISCOVER mode and then the DHCPD daemon correctly recognized that this client was on a new interface/VLAN and handed it a valid IP address for that interface/VLAN. ProblemType: Bug DistroRelease: Ubuntu 20.04 Package: isc-dhcp-server 4.4.1-2.1ubuntu5.20.04.2 [modified: usr/bin/omshell] ProcVersionSignature: Ubuntu 5.4.0-94.106-generic 5.4.157 Uname: Linux 5.4.0-94-generic x86_64 ApportVersion: 2.20.11-0ubuntu27.21 Architecture: amd64 CasperMD5CheckResult: pass Date: Fri Jan 28 12:24:05 2022 InstallationDate: Installed on 2021-06-29 (212 days ago) InstallationMedia: Ubuntu-Server 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731) ProcEnviron: SHELL=/bin/bash TERM=xterm-color XDG_RUNTIME_DIR=<set> PATH=(custom, user) SourcePackage: isc-dhcp UpgradeStatus: No upgrade log present (probably fresh install) modified.conffile..etc.dhcp.dhcpd6.conf: [modified] mtime.conffile..etc.dhcp.dhcpd.conf: 2022-01-28T12:09:41.747865 mtime.conffile..etc.dhcp.dhcpd6.conf: 2019-01-03T15:05:49 ** Affects: isc-dhcp (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug focal uec-images -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1959445 Title: DHCPD gets confused about what IPs should be handed out on what interfaces To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/isc-dhcp/+bug/1959445/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs