Hello,
Looking for detailed instructions how to modify the <default> address space and maybe other settings for User Mode Networking in QEMU-KVM. Looked around and so far unable to find clear instructions.
Problem:
Had QEMU-KVM working more or less as expected for a few days…
Then the Public Network I frequently connect to changed their address space to the Default Class A Private network using the default subnet mask, grabbing <all> addresses.
For those who may not be familiar with the Default Class A Private Network space, if you use the default subnet mask there is only one possible network while maximizing the number of possible Host addresses.
The result is if you have any <other> networks behind the Shared Network to the Internet also configured with a Class A network, all of a sudden routing is impossible because both/all networks share the same address space. This impacts QEMU-KVM because its virtual networks are all by default configured with Class A Private Network address spaces.
The Required Fix:
So, it looks like I need to modify the network settings for my virtual networks and I need step by step instructions. The first network I want to modify is User Mode Netoworking.
First Attempt:
Found the openSUSE QEMU-KVM page
https://doc.opensuse.org/documentation/htmlsingle/openSUSE/opensuse-kvm.html#ex.qemu.net.usermode.iprange
Based on that info, attempted to change to a Class B Private Network
qemu-kvm -net user,net=176.27.0.0/12,host=176.27.2.2,dhcpstart=176.27.0.20
But it seems that command only launches a VM likely with new settings, complaining about “no NIC found” which was really surprising since I don’t think the command can be confused with launching a VM (unless someone sees an error in my command).
TIA,
TSU