My internal network (4 nodes, all running on Ubuntu 24.04.3 + switch / router with OpenWrt) stopped working a couple of hours ago. Suddenly, none (!) of the nodes has had an IPv4 address. I’ve got dnsmasq (DHCP + DNS) running on the router. It used to work flawlessly, but right after the network crash, I found two strange things in the logs:
Flaw #1: two different IP ranges, even if only the first one appears in the dnsmasq.conf. So, where does the second range come from:
Nov 27 17:27:12 dnsmasq-dhcp[1]: 2589069141 available DHCP range: 10.20.0.11 -- 10.20.0.127
Nov 27 17:27:12 dnsmasq-dhcp[1]: 2589069141 available DHCP range: 10.20.0.2 -- 10.20.0.151
Flaw #2: I can see a discover and an offer in the logs, but the corresponding request and ACK messages are always (!) missing:
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 client provides name: blade3n4
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 DHCPDISCOVER(pci0) 10.20.0.14 02:a4:f1:25:38:0a
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 tags: pci0
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 DHCPOFFER(pci0) 10.20.0.14 02:a4:f1:25:38:0a
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 requested options: 1:netmask, 2:time-offset, 6:dns-server, 12:hostname,
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 requested options: 15:domain-name, 26:mtu, 28:broadcast, 121:classless-static-route,
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 requested options: 3:router, 33:static-route, 40:nis-domain,
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 requested options: 41:nis-server, 42:ntp-server, 119:domain-search,
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 requested options: 249, 252, 17:root-path
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 next server: 10.20.0.1
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 1 option: 53 message-type 2
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 54 server-identifier 10.20.0.1
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 51 lease-time 5m
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 58 T1 2m30s
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 59 T2 4m22s
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 28 broadcast 10.20.0.255
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 3 option: 15 domain-name lan
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 42 ntp-server 192.168.178.1
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 6 dns-server 10.20.0.1
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 3 router 10.20.0.1
Nov 27 17:27:13 dnsmasq-dhcp[1]: 2589069141 sent size: 4 option: 1 netmask 255.255.255.0
No matter which node, I don’t get the desired IP:
5: pci0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 65202 qdisc fq_codel state DOWN group default qlen 1000
link/ether 02:9f:f1:8e:cb:0a brd ff:ff:ff:ff:ff:ff
I haven’t changed my dnsmasq.conf in the meantime:
listen-address=::1,127.0.0.1,10.20.0.1,fdb0:557a:1911:10::1
interface=eth_pci
dhcp-option=option:netmask,255.255.255.0
dhcp-option=option:router,10.20.0.1
dhcp-option=option:dns-server,10.20.0.1
dhcp-option=option:ntp-server,192.168.178.1
dhcp-range=10.20.0.11,10.20.0.127,24h
no-resolv
server=192.168.178.1
log-dhcp
log-queries
Neither have I updated by system.
Note: I’ve already had a similar issue on an older machine (mid-air crash because of no more DHCP leases), which was never solved.
Update: A reboot of the whole infrastructure (router + all four nodes) brought my network back to life. But: I still don’t know the cause of the crash, and I really don’t wanna happen this for a second time.
