Ubuntu 20.04: when trying to create bridge interface, getting two interfaces with same IP address and duplicated default routes

[Konstantin Boyandin]

Hello,

When trying to create a network bridge (via netplan), I get strange 
results on Ubuntu 20.04.

Netplan configuration:
===== netplan configuration below
network:
   version: 2
   renderer: networkd

   ethernets:
     eno1:
       dhcp4: false
       dhcp6: false

   bridges:
     br0:
       interfaces: [eno1]
       addresses: [10.20.0.21/24]
       gateway4: 10.20.0.1
       nameservers:
         search: [example.com]
         addresses: [10.20.0.1,10.20.0.10]
       dhcp4: false
       dhcp6: false
===== netplan configuration above

When I run "netplan try", I see:

** (generate:2332): WARNING **: 12:54:41.673: Problem encountered while 
validating default route consistency.Please set up multiple routing 
tables and use `routing-policy` instead.
Error: Conflicting default route declarations for IPv4 (table: main, 
metric: default), first declared in br0 but also in eno1

If I reboot the system, the "route" shows the below:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use 
Iface
default         10.20.0.1       0.0.0.0         UG    0      0        0 br0
default         10.20.0.1       0.0.0.0         UG    0      0        0 eno1
10.20.0.0        0.0.0.0        255.255.255.0   U     0      0        0 br0
10.20.0.0        0.0.0.0        255.255.255.0   U     0      0        0 eno1

The system remains usable, but the configuration is obviously abnormal.

"networkctl" displays:

networkctl
IDX LINK TYPE     OPERATIONAL SETUP
   1 lo   loopback carrier     unmanaged
   2 eno1 ether    routable    configured
   3 br0  bridge   routable    configured

Is it possible to have the bridged original interface enslaved, without 
duplicating IPs and routes?

-- 
Sincerely,

Konstantin Boyandin