Bug 651898 – sys-apps/systemd-238-r2 - identical MAC address for br0 on two systems

• Status: RESOLVED INVALID
• Product: Gentoo Linux

[Description Juergen Rose 2018-03-29 09:53:31 UTC]

I have here two systems with a bridged inerface. The first is lynx, configured with br0.netdev, br0_eth.network and  br0.network:

root@lynx:/etc/systemd/network(66)# ls
br0_eth.network  br0.netdev  br0.network

root@lynx:/etc/systemd/network(67)# cat br0.netdev
[NetDev]
Name=br0
Kind=bridge

root@lynx:/etc/systemd/network(68)# cat br0.network
[Match]
Name=br0

[Network]
#Bridge=br0
DNS=192.168.201.253
DNS=192.168.64.10
Address=192.168.201.33/24

[Route]
Gateway=192.168.201.253

root@lynx:/etc/systemd/network(69)# cat br0_eth.network
[Match]
Name=eth*

[Network]
Bridge=br0


root@lynx:/etc/systemd/network(70)# ip addr show
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: sit0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN group default qlen 1000
    link/sit 0.0.0.0 brd 0.0.0.0
4: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UP group default qlen 1000
    link/ether c8:5b:76:53:a1:40 brd ff:ff:ff:ff:ff:ff
5: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN group default qlen 1000
    link/ether f0:d5:bf:33:aa:68 brd ff:ff:ff:ff:ff:ff
7: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether d6:f2:8f:85:eb:55 brd ff:ff:ff:ff:ff:ff
    inet 192.168.201.33/24 brd 192.168.201.255 scope global br0
       valid_lft forever preferred_lft forever
    inet6 fe80::d4f2:8fff:fe85:eb55/64 scope link 
       valid_lft forever preferred_lft forever


The second system is lynxold, configured with br0.netdev, BridgeEth.network and MyBridge.network:

root@lynxold:/etc/systemd/network(62)# ls
br0.netdev  BridgeEth.network  BridgeVbox.network  MyBridge.network

root@lynxold:/etc/systemd/network(62)# ls
br0.netdev  BridgeEth.network  BridgeVbox.network  MyBridge.network

root@lynxold:/etc/systemd/network(63)# cat br0.netdev
[NetDev]
Name=br0
Kind=bridge

root@lynxold:/etc/systemd/network(64)# cat MyBridge.network
[Match]
Name=br0

[Network]
DNS=192.168.201.253
DNS=141.89.64.1
DNS=8.8.4.4
Address=192.168.201.31/24

[Route]
Gateway=192.168.201.253

root@lynxold:/etc/systemd/network(65)# cat BridgeEth.network 
[Match]
Name=eth*

[Network]
Bridge=br0

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: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UP group default qlen 1000
    link/ether 3c:97:0e:2a:62:ec brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN group default qlen 1000
    link/ether 00:24:d7:88:4b:dc brd ff:ff:ff:ff:ff:ff
4: wwan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 02:15:e0:ec:01:00 brd ff:ff:ff:ff:ff:ff
7: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether d6:f2:8f:85:eb:55 brd ff:ff:ff:ff:ff:ff
    inet 192.168.201.31/24 brd 192.168.201.255 scope global br0
       valid_lft forever preferred_lft forever
    inet6 fe80::d4f2:8fff:fe85:eb55/64 scope link 
       valid_lft forever preferred_lft forever




I.e., there is the same MAC address d6:f2:8f:85:eb:55 for br0 in both systems.
This blocks at least the communication between lynx and lynxold. I assume this behaviour is based on identical /etc/machine-id files on both systems (the root partition of lynx was cloned from lynxold and only IP-Addresses and hostnames were modified). Should I only modify /etc/machine-id at lynx or do something else?

[Comment 1 Jeroen Roovers (RETIRED) 2018-03-29 10:08:54 UTC]

Is this a misplaced support request?

[Comment 2 Juergen Rose 2018-03-29 10:20:23 UTC]

Creating an empty /etc/machine-id and rebooting solved this issue.

[Comment 3 Mike Gilbert 2018-03-29 15:51:40 UTC]

/etc/machine-id needs to be unique on every machine.