I try to figure out how to set up two logical network interfaces (at one physical interface) with separate MAC addresses on a Linux machine.
My first attempt was to use macvlan which seemed to work at first:
[root@localhost ~]# ip link add link enp0s3 name veth0 type macvlan [root@localhost ~]# ip link set veth0 up [root@localhost ~]# dhclient veth0 [root@localhost ~]# ifconfig enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.1.6 netmask 255.255.255.0 broadcast 192.168.1.255 inet6 fe80::a00:27ff:fe3b:d08b prefixlen 64 scopeid 0x20<link> ether 08:00:27:3b:d0:8b txqueuelen 1000 (Ethernet) RX packets 356 bytes 58787 (57.4 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 210 bytes 24203 (23.6 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 veth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.1.11 netmask 255.255.255.0 broadcast 192.168.1.255 inet6 fe80::2462:42ff:fecb:5090 prefixlen 64 scopeid 0x20<link> ether 26:62:42:cb:50:90 txqueuelen 0 (Ethernet) RX packets 83 bytes 9099 (8.8 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 34 bytes 3871 (3.7 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
However, when scanning the local network from another machine, both interfaces (192.168.1.6 and 192.168.1.11) are shown to have the same MAC address 08:00:27:3b:d0:8b.
Any ideas if this is possible? What is the use of macvlan if I cannot use it for this purpose?
As suggested by Otheus, I tried the same as before with the settings
sysctl -w net.ipv4.conf.all.arp_ignore=1 sysctl -w net.ipv4.conf.all.arp_announce=2
This apparently makes interfaces to reply only to those arp requests explicitely directed to them.
In my setup, this led to failing DHCP requests to assign an IP address to veth0. With a static IP address on veth0, I could not reach this address from other hosts in the network (I tried arp/nmap/ping).
My (preliminary) conclusion is that it is not possible to have a virtual interface with a different MAC address on the same subnet. However, I still wonder what is the exact purpose of macvlan then, and why I see the virtual interface with its own MAC address on the local machine (where I set up the virtual interface), but not from other machines.