Proxmox 5.1. The second network card does not work in the guest. Where to dig?

Question

linux

Hello. There is Proxmox 5.1. The server has two network cards. On one of them, vmbr0 was created, which is distributed to guests, this thing works. It has some kind of virtual machine that needs to communicate directly with another bar metal server through a separate network interface, for which I want to use a second network card in Proxmox. The problem is that I create a vmbr1 that bridges to the enp2s0 network interface (this is the second unused network card), forward it to the guest, configure it as it should, but the guest does not see the "iron server", in any way. As well as the "iron" server does not see the virtual guest. Maybe someone came across? Smoked half of Google, but did not find a solution.
Well, here is the network config from Proxmox

cat /etc/network/interfaces
# network interface settings; autogenerated
# Please do NOT modify this file directly, unless you know what
# you're doing.
#
# If you want to manage part of the network configuration manually,
# please utilize the 'source' or 'source-directory' directives to do
# so.
# PVE will preserve these directives, but will NOT its network
# configuration from sourced files, so do not attempt to move any of
# the PVE managed interfaces into external files!

auto lo
iface lo inet loopback

allow-hotplug iface enp2s0
iface enp2s0 inet manual
allow-hotplug iface enp1s0
iface enp1s0 inet manual

auto vmbr0
iface vmbr0 inet static
  address  192.168.88.188
  netmask  255.255.255.0
  gateway  192.168.88.1
  bridge_ports enp1s0
  bridge_stp off
  bridge_fd 0

auto vmbr1
iface vmbr1 inet manual
  bridge_ports enp2s0
  bridge_stp off
  bridge_fd 0

Answer 1

Maybe I misunderstood... I don't understand who should be pinged....
You initialize the enp1s0 and enp2s0 interfaces.
On each you create bridge_ports vmbr0 and vmbr1
, respectively.
it is necessary to allow the circulation of packages enp1s0<->enp2s0 here

Answer 2

brctl show look
, most likely you did not restart the VM after the vmbr1 settings
in a good way, so that the VM saw the changes without restarting after

/etc/init.d/networking restart

interfaces should be something like

iface vmbr1 inet manual
bridge_ports enp2s0 tap100i1