Why does the network break when restarting on Proxmox?

Question

Computer networks

eth0 - physical card
vmbr0 - bridge to it
vmbr1 - bridge for virtual machines
Everything works fine until the first network restart, after that virtual machines from 192.168.1.x stop pinging
Interface configuration:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual

auto vmbr0
iface vmbr0 inet static
  address  a.b.c.d
  broadcast e.f.g.h
  netmask  255.255.255.224
  gateway  k.l.m.n
  bridge_ports eth0
  bridge_stp off
  bridge_fd 1
  bridge_hello 2
  bridge_maxage 12

auto vmbr1
iface vmbr1 inet static
  address  192.168.1.1
  netmask  255.255.255.0
  bridge_ports none
  bridge_stp off
  bridge_fd 0
  post-up echo 1 > /proc/sys/net/ipv4/ip_forward
  post-up iptables -t nat -A POSTROUTING -s '192.168.1.0/24' -o vmbr0 -j MASQUERADE
  post-up iptables-restore /etc/network/firewall.rules
  post-down iptables -t nat -D POSTROUTING -s '192.168.1.0/24' -o vmbr0 -j MASQUERADE

What happens when you try to lower and raise vmbr1:

[email protected] ~ # ifup vmbr1
Waiting for vmbr1 to get ready (MAXWAIT is 2 seconds).
RTNETLINK answers: File exists
Failed to bring up vmbr1.
[email protected] ~ # ifdown vmbr1
ifdown: interface vmbr1 not configured

This shows vmbr1 as UP but doesn't work. Pings only 192.168.1.1 (himself)

vmbr1     Link encap:Ethernet  HWaddr 5e:12:36:ca:29:84  
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::5c12:36ff:feca:2984/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1966 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:82924 (80.9 KiB)

RX bytes = 0 and there is no internet on the VMs.
I tried this - the bridges are removed normally, but the effect is the same, there is no connection:

ip link set vmbr1 down
ip link set vmbr0 down
brctl delbr vmbr1
brctl delbr vmbr0
service networking restart

On the Internet they write - "reboot and everything will be fine", but I'm not satisfied with this approach to the hypervisor. Where is the mistake?

Answer 1

why do you need this garden with nat and 2nd bridge?

Answer 2

Well, why stop him?
And why are you virtualok interfaces then into it after you threw them out. That is, they must magically appear there themselves

Answer 3

if there is static on virtual machines, it makes sense to prescribe allow-hotplug, not auto