Intermittent network on one of three Debian VMs

[Touros Spoon <touros.spoon@xxxxxxxxx>]

Hi, I'm new to Xen project, so there is the distinct possibility I have 
done something stupid or overlooked something simple...
Setup:

Hp DL160 G6 Server

2 x xeon x5675 6 core CPU

48GB Ram

Dual onboard 1Gb NIC (only 1 in use)


xen installed through: apt-get install xen-system


Environment:

small home office. Server is in a rackmount cabinet with 3 other 
servers, connected together through an off the shelf netgear 8 port 
gigabit switch. Connectivity to all physical servers is fine (<0.05ms ping)

Dom0:

=====

Debian 10 minimal (net inst)

Hostname: hs1

Ram: 4GB

vcpus: 2

NIC: enp5s0f0

Bridge: xenbr0


DomU 1:

Debian 10

Hostname: dc1

Ram:  4GB

vcpus: 2


DomU2:

Debian 10

Hostname: dev1

Ram: 24GB

vcpus: 12


DomU3:

Debian 10

Hostname: gs1

Ram: 14GB

vcpus: 8


Problem:

I can connect to all of the DomUs using xl console <dc1|dev1|gs1>

I can ping hs1 (Dom0), dc1 and dev1 ok, but gs1 locks up and either 
doesn't reply at all, or does reply after almost a minute and whereas 
the ping times for hs1, dc1 & dev1 are in the ~0.05ms range, the ping 
time for gs1 is > 40ms. So, something is clearly wrong here...
I can ssh to hs1, dc1 and dev1 fine , but not gs1. It *does* connect 
maybe once out of 20 tries but it disconnects randomly on the rare few 
occasions I am able to connect to it through ssh and there is horrible 
latency between
The ssh configuration is the same for all of the DomUs and HS1.


There is currently no load on any of the DomU or Dom0 as I don't want to 
proceed with installing the various components I need, until I've 
resolved this network issue; there isn't any point in proceeding if I 
cannot connect!
As I don't know very much about Xen, I wondered if there was something 
else I had to do to the bridge to make it work with multiple DomUs as 
the bridge worked fine until I added that last DomU (gs1)...
Any help or advice would be greatly appreciated.

TS.


My /etc/network/interfaces file:


# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo xenbr0
iface lo inet loopback

# The primary network interface

iface enp5s0f0 inet manual

# Setup Xen Interface Bridge
auto xenbr0
iface xenbr0 inet static
        bridge_ports enp5s0f0
                address 192.168.1.31
                broadcast 192.168.1.255
                netmask 255.255.255.0
                gateway 192.168.1.1