VM "Tap" Interface

[masterdaweb]

Hello,

When I used "ifconfig -a", I realized that the MAC Address for "TapXXX" interface is different from the MAC Address configured in Proxmox GUI:






Shouldn't it be the same ?

 

[fabian]

no, the network device inside the container gets the configured MAC.

 

[lethargos]

Hi, could you possibly expand on this? Why are they not the same? At first sight, I'd say they should be one and the same and the host should have a switch-type of view of the network interfaces of the vms. Why is this happening? I've been trying to understand this for some time, but I still haven't been able to find an answer.

 

[fabian]

Hi, could you possibly expand on this? Why are they not the same? At first sight, I'd say they should be one and the same and the host should have a switch-type of view of the network interfaces of the vms. Why is this happening? I've been trying to understand this for some time, but I still haven't been able to find an answer.

the container runs in a different network namespace, so we use a veth pair to bridge that "gap". the configured MAC is the one we want the container to see (e.g., for static DHCP, ...), so we set it on the veth peer inside the container network namespace.

 

[lethargos]

And how is the mac address that the host sees being used?

 

[wbumiller]

It's not. It would only be used if you remove the veth (or tap for VMs) device from the bridge, configure an IP address on that device directly and used that to communicate with the guest.

veth or tap devices behave like virtual ethernet cards. What you see on the host is your host side of it. The guest sees the other side. Every such card has a MAC addres. Since they're usually on a bridge, the mac address is usually unused.

 

[lethargos]

Danke sehr!