[solved] Dnsmasq-dhcp fail to offer IPv4 (wrong server-ID)

Installing and Using OpenWrt Network and Wireless Configuration
1

Hi,

yesterday I updates my OpenWrt 23.05.2 r23630-842932a63d installatin with dnsmasq 2.90-2

Now I am dicovering an ubuntu virtuel machine doesn´t get IPv4 adress anymore. IPv6 is working.

OpenWRT log says:

Mon Dec 30 12:24:23 2024 daemon.warn odhcpd[2008]: No default route present, overriding ra_lifetime!
Mon Dec 30 12:24:24 2024 daemon.info dnsmasq-dhcp[1]: DHCPDISCOVER(br-lan) 00:0c:29:03:41:78
Mon Dec 30 12:24:24 2024 daemon.info dnsmasq-dhcp[1]: DHCPOFFER(br-lan) 192.168.24.137 00:0c:29:03:41:78
Mon Dec 30 12:24:24 2024 daemon.info dnsmasq-dhcp[1]: DHCPREQUEST(br-lan) 10.0.0.11 00:0c:29:03:41:78
Mon Dec 30 12:24:24 2024 daemon.info dnsmasq-dhcp[1]: DHCPNAK(br-lan) 10.0.0.11 00:0c:29:03:41:78 wrong server-ID

I restartet OpenWRT router, did a cold boot and also put client network interface up/down.

My normal network ip range ist 192.168.24.0/24 first dhcp ip starts at 192.168.24.100

What is going wrong here? Why ip 10.0.0.11 ? What does wrong server-ID meen?

Help appreciated.

thx
Rossi

2

That can be seen if you are running two DHCP servers.

3

Ok, I didn´t figure how to check if I got two dhcp server?

Network -> Interfaces -> lan -> edit -> DHCP Server

is set

my other network interfaces doesn´t have DHCP Server active.
Maybe wireless network? I doesn´t find any option for that? I assume wireless is using lan dhcp server too?

thx for help

4

I just have to define Listen interfaces only for lan.

Network -> DHCP and DNS -> devices and ports -> Listen interfaces -> lan

Here we go

5

It's not quite over yet.

Wed Jan  1 12:57:55 2025 daemon.warn odhcpd[2009]: No default route present, overriding ra_lifetime!
Wed Jan  1 12:57:55 2025 daemon.info dnsmasq-dhcp[1]: DHCPDISCOVER(br-lan) 00:0c:29:03:41:78
Wed Jan  1 12:57:55 2025 daemon.info dnsmasq-dhcp[1]: DHCPOFFER(br-lan) 192.168.24.137 00:0c:29:03:41:78
Wed Jan  1 12:57:55 2025 daemon.info dnsmasq-dhcp[1]: DHCPREQUEST(br-lan) 10.0.0.11 00:0c:29:03:41:78
Wed Jan  1 12:57:55 2025 daemon.info dnsmasq-dhcp[1]: DHCPNAK(br-lan) 10.0.0.11 00:0c:29:03:41:78 wrong server-ID

I also excluded all other interfaces

Wed Jan  1 13:02:09 2025 daemon.info dnsmasq[1]: exiting on receipt of SIGTERM
Wed Jan  1 13:02:09 2025 daemon.info dnsmasq[1]: started, version 2.90 cachesize 150
Wed Jan  1 13:02:09 2025 daemon.info dnsmasq[1]: compile time options: IPv6 GNU-getopt no-DBus UBus no-i18n no-IDN DHCP no-DHCPv6 no-Lua TFTP no-conntrack no-ipset no-nftset no-auth no-cryptohash no-DNSSEC no-ID loop-detect inotify dumpfile
Wed Jan  1 13:02:09 2025 daemon.info dnsmasq[1]: UBus support enabled: connected to system bus
Wed Jan  1 13:02:09 2025 daemon.info dnsmasq-dhcp[1]: DHCP, IP range 192.168.24.100 -- 192.168.24.249, lease time 12h
Wed Jan  1 13:02:09 2025 daemon.info dnsmasq-dhcp[1]: DHCP, sockets bound exclusively to interface br-lan

Now dhcp is exclusively for br-lan

I still got

Wed Jan  1 13:06:06 2025 daemon.info dnsmasq-dhcp[1]: DHCPDISCOVER(br-lan) 00:0c:29:03:41:78
Wed Jan  1 13:06:06 2025 daemon.info dnsmasq-dhcp[1]: DHCPOFFER(br-lan) 192.168.24.137 00:0c:29:03:41:78
Wed Jan  1 13:06:06 2025 daemon.info dnsmasq-dhcp[1]: DHCPREQUEST(br-lan) 10.0.0.11 00:0c:29:03:41:78
Wed Jan  1 13:06:06 2025 daemon.info dnsmasq-dhcp[1]: DHCPNAK(br-lan) 10.0.0.11 00:0c:29:03:41:78 wrong server-ID

My questions are still valid.

6

Install nmap on the Ubuntu and run nmap --script broadcast-dhcp-discover

https://www.ubuntu18.com/install-nmap-ubuntu/
https://nmap.org/nsedoc/scripts/broadcast-dhcp-discover.html#usage

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