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by **fitscher** » 2020-11-10 11:49

Dear people,
i have a problem where i can't get any further (due to my limited Linux knowledge). After the upgrade (apt upgrade, apt full-upgrade) from stretch to buster the unbound server did not answer DNS requests anymore. And after some troubleshooting i realized a second ip address on eno2 (lan) adapter.

Code: Select all: $ dig dnswl.org @192.168.1.1

Error message:

Code: Select all: ;; reply from unexpected source: 192.168.1.173#53, expected 192.168.1.1#53

I got the unbound server running again by adding "interface-automatic: yes" to the configuration file /etc/unbound/unbound.conf.

Here is some additional information:

1.# netstat -lpn | grep 173

Code: Select all: udp 0 0 192.168.1.173:123 0.0.0.0:* 1751/ntpd

2. # ip adr

Code: Select all: ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000 link/ether b0:5a:da:87:b1:2c brd ff:ff:ff:ff:ff:ff inet 172.16.1.2/16 brd 172.16.255.255 scope global noprefixroute eno1 valid_lft forever preferred_lft forever inet6 fd00::3dbb:3020:1bbe:e6a8/64 scope global dynamic mngtmpaddr noprefixroute valid_lft 6715sec preferred_lft 3115sec inet6 fe80::b25a:daff:fe87:b12c/64 scope link valid_lft forever preferred_lft forever 3: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000 link/ether b0:5a:da:87:b1:2d brd ff:ff:ff:ff:ff:ff inet 192.168.1.1/24 brd 192.168.1.255 scope global eno2 valid_lft forever preferred_lft forever inet 192.168.1.173/24 brd 192.168.1.255 scope global secondary noprefixroute eno2 valid_lft forever preferred_lft forever inet6 fe80::b25a:daff:fe87:b12d/64 scope link valid_lft forever preferred_lft forever 4: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 100 link/none inet 10.8.0.1/24 brd 10.8.0.255 scope global tun0 valid_lft forever preferred_lft forever inet6 fe80::9bb:c208:421b:f191/64 scope link stable-privacy valid_lft forever preferred_lft forever

3. ip addr show eno2

Code: Select all: 3: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000 link/ether b0:5a:da:87:b1:2d brd ff:ff:ff:ff:ff:ff inet 192.168.1.1/24 brd 192.168.1.255 scope global eno2 valid_lft forever preferred_lft forever inet 192.168.1.173/24 brd 192.168.1.255 scope global secondary noprefixroute eno2 valid_lft forever preferred_lft forever inet6 fe80::b25a:daff:fe87:b12d/64 scope link valid_lft forever preferred_lft forever

4. cat /etc/network/interfaces

Code: Select all: # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). source /etc/network/interfaces.d/* # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eno1 allow-hotplug eno1 iface eno1 inet static address 172.16.1.2 netmask 255.255.0.0 network 172.16.0.0 broadcast 172.16.255.255 gateway 172.16.1.1 auto eno2 allow-hotplug eno2 iface eno2 inet static address 192.168.1.1 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255

Does anybody have a tip for me on how to find out where the additional address (192.168.1.173) is generated? With journalctl -b, dmesg or syslog i can see an entry that this address is retrieved via dhcp.

Sometimes the network connections (ssh) to the server are hanging for a couple seconds.

thank you
kind regards thomas

by **fitscher** » 2020-11-10 16:38

i have now blocked the mac address b0:5a:da:87:b1:2d of eno2 interface in /etc/dhcp/dhcpd.conf. So a private dummy address was assigned. But I still do not know where this dhcp request comes from?

# ip addr show eno2

Code: Select all: 3: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000 link/ether b0:5a:da:87:b1:2d brd ff:ff:ff:ff:ff:ff inet 192.168.1.1/24 brd 192.168.1.255 scope global eno2 valid_lft forever preferred_lft forever inet 169.254.140.73/16 brd 169.254.255.255 scope global noprefixroute eno2 valid_lft forever preferred_lft forever inet6 fe80::daa1:7841:deb3:9b8/64 scope link valid_lft forever preferred_lft forever inet6 fe80::b25a:daff:fe87:b12d/64 scope link valid_lft forever preferred_lft forever

by **sickpig** » 2020-11-10 18:07

Additional ip shouldn't matter, what matters is what are you using as your dns ip? What is in your /etc/reoslv.conf? Why do you think dhcp is involved? And lastly what is the status of NetworkManager.service?

by **fitscher** » 2020-11-10 18:59

sickpig wrote:Additional ip shouldn't matter, what matters is what are you using as your dns ip? What is in your /etc/reoslv.conf? Why do you think dhcp is involved? And lastly what is the status of NetworkManager.service?

thank you for your answer.

Additional ip shouldn't matter,

unfortunately it matters, see my remark about unbound dns server, DNS queries didn't work anymore and also other processes/daemons (ntpd, syncthing..) will hook to this additional ip.

what matters is what are you using as your dns ip?

i am using the ip address 192.168.1.1 as DNS, which is distributed to the clients via dhcp. It is the address of the servers lan interface on which unbound is listening.

What is in your /etc/reoslv.conf?

for unbound it is set to "manual mode" and i configured in /etc/systemd/resolved.conf.

Code: Select all: [Resolve] DNS=127.0.0.1 FallbackDNS=172.16.1.1 #Domains= #LLMNR=yes MulticastDNS=no #DNSSEC=allow-downgrade #DNSOverTLS=no #Cache=yes DNSStubListener=no #ReadEtcHosts=yes

Why do you think dhcp is involved?

because it is in the logfile (syslog)

And lastly what is the status of NetworkManager.service?

Networkmanager is not running, it is a headless server

I wanted to notice again, that everything worked before the update. Actually i am just looking for a way to find out which process is starting this dhcp client again and again?
kind regards
Thomas

by **reinob** » 2020-11-10 19:04

fitscher wrote:Does anybody have a tip for me on how to find out where the additional address (192.168.1.173) is generated? With journalctl -b, dmesg or syslog i can see an entry that this address is retrieved via dhcp.

Could you post the relevant log entries?

This would help in identifying which dhcp client (there are many possibilities) is doing that, so that you can disable/configure dhcp accordingly.

by **fitscher** » 2020-11-10 19:46

reinob wrote:
fitscher wrote:Does anybody have a tip for me on how to find out where the additional address (192.168.1.173) is generated? With journalctl -b, dmesg or syslog i can see an entry that this address is retrieved via dhcp.

Could you post the relevant log entries?

This would help in identifying which dhcp client (there are many possibilities) is doing that, so that you can disable/configure dhcp accordingly.

thx

log entry:
Logs Entry at 2020-11-10 20:54:27
dhcpd
DHCPDISCOVER from b0:5a:da:87:b1:2d via eno2: network 192.168.1.0/24: no free leases

_BOOT_ID

_CAP_EFFECTIVE

_CMDLINE

/usr/sbin/dhcpd -4 -q -cf /etc/dhcp/dhcpd.conf eno2

_COMM

_EXE

_GID

_HOSTNAME

MACHINE_ID

_PID

_SOURCE_REALTIME_TIMESTAMP

_SYSTEMD_CGROUP

_SYSTEMD_INVOCATION_ID

_SYSTEMD_SLICE

_SYSTEMD_UNIT

TRANSPORT

_UID

__CURSOR

__MONOTONIC_TIMESTAMP

__REALTIME_TIMESTAMP

this log entry comes every minute

by **fitscher** » 2020-11-10 20:04

thank you @reinob und sickpig for your help.

there was a dhcpcd.service enabled with systemd which was not enabled before the update???

# systemctl status dhcpcd.service

Code: Select all: ● dhcpcd.service - DHCP Client Daemon Loaded: loaded (/lib/systemd/system/dhcpcd.service; enabled; vendor preset: enabled) Active: active (running) since Tue 2020-11-10 17:30:42 CET; 4h 8min ago Docs: man:dhcpcd(8) Process: 605 ExecStart=/usr/sbin/dhcpcd (code=exited, status=0/SUCCESS) Main PID: 686 (dhcpcd) Tasks: 1 (limit: 9830) Memory: 4.1M CGroup: /system.slice/dhcpcd.service └─686 /usr/sbin/dhcpcd Nov 10 17:30:43 proliant dhcpcd[686]: eno1: Router Advertisement from fe80::5e49:79ff:fedd:a4c9 Nov 10 17:30:43 proliant dhcpcd[686]: eno1: adding address fd00::3dbb:3020:1bbe:e6a8/64 Nov 10 17:30:43 proliant dhcpcd[686]: eno1: adding route to fd00::/64 Nov 10 17:30:43 proliant dhcpcd[686]: eno1: soliciting a DHCPv6 lease Nov 10 17:30:47 proliant dhcpcd[686]: eno2: probing for an IPv4LL address Nov 10 17:30:47 proliant dhcpcd[686]: eno2: DHCP lease expired Nov 10 17:30:47 proliant dhcpcd[686]: eno2: soliciting a DHCP lease Nov 10 17:30:52 proliant dhcpcd[686]: eno2: using IPv4LL address 169.254.140.73 Nov 10 17:30:52 proliant dhcpcd[686]: eno2: adding route to 169.254.0.0/16 Nov 10 17:30:54 proliant dhcpcd[686]: eno2: no IPv6 Routers available

i disabled it and now it is ok again:

# ip addr show eno2

Code: Select all: 3: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000 link/ether b0:5a:da:87:b1:2d brd ff:ff:ff:ff:ff:ff inet 192.168.1.1/24 brd 192.168.1.255 scope global eno2 valid_lft forever preferred_lft forever inet6 fe80::b25a:daff:fe87:b12d/64 scope link valid_lft forever preferred_lft forever

thank you again and have a nice day

regards thomas

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