what I want to do:
virtual machine (guest) with two Ethernet interfaces.
this guest must have an Internet connection and both its Ethernet interfaces are accessible from the KVM-host

ISP-----TP_link_router----KVM---(GUEST)
TP_link_router - Home Router(with DHCP server). 192.168.1.1(privet ip)
KVM -Leap15.3 with br0(192.168.1.2)
GUEST -RockiLinux with 2 Ethernet Interfaces

About KVM:
Virtual Networks:
name="routednet"
Network:
"192.168.100.0/24"
DHCP range:
"192.168.100.128-192.168.100.254"
Forwarding:
"Routed network"
Code:
<network>
  <name>routednet</name>
  <uuid>c80e591b-13bb-43f1-9cdc-e62fb1b3b607</uuid>
  <forward mode="route"/>
  <bridge name="virbr1" stp="on" delay="0"/>
  <mac address="52:54:00:fa:5f:21"/>
  <domain name="routednet"/>
  <ip address="192.168.100.1" netmask="255.255.255.0">
    <dhcp>
      <range start="192.168.100.128" end="192.168.100.254"/>
    </dhcp>
  </ip>
</network>
About GUEST Ethernet interfaces:
Code:
<interface type="network">
  <mac address="52:54:00:92:b5:43"/>
  <source network="routednet"/>
  <model type="virtio"/>
  <link state="up"/>
  <address type="pci" domain="0x0000" bus="0x01" slot="0x00" function="0x0"/>
</interface>
and
Code:
<interface type="network">
  <mac address="52:54:00:de:34:44"/>
  <source network="routednet"/>
  <model type="virtio"/>
  <link state="up"/>
  <address type="pci" domain="0x0000" bus="0x07" slot="0x00" function="0x0"/>
</interface>
This is in the GUEST:
Code:
[root@rk009 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:92:b5:43 brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.254/24 brd 192.168.100.255 scope global dynamic noprefixroute enp1s0
       valid_lft 3552sec preferred_lft 3552sec
    inet6 fe80::5054:ff:fe92:b543/64 scope link 
       valid_lft forever preferred_lft forever
3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:de:34:44 brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.217/24 brd 192.168.100.255 scope global dynamic noprefixroute enp7s0
       valid_lft 3552sec preferred_lft 3552sec
    inet6 fe80::5054:ff:fede:3444/64 scope link 
       valid_lft forever preferred_lft forever
This is from SERVER KVM ping to the GUEST and ARP table:
Code:
> ping 192.168.100.217 -c1
PING 192.168.100.217 (192.168.100.217) 56(84) bytes of data.
64 bytes from 192.168.100.217: icmp_seq=1 ttl=64 time=0.237 ms

--- 192.168.100.217 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.237/0.237/0.237/0.000 ms
ksr@kap1:~> ping 192.168.100.254 -c1
PING 192.168.100.254 (192.168.100.254) 56(84) bytes of data.
64 bytes from 192.168.100.254: icmp_seq=1 ttl=64 time=0.275 ms

--- 192.168.100.254 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.275/0.275/0.275/0.000 ms

# ip neigh show
192.168.1.1 dev br0 lladdr e4:be:ed:df:c1:8b DELAY
192.168.100.217 dev virbr1 lladdr 52:54:00:92:b5:43 STALE
192.168.100.254 dev virbr1 lladdr 52:54:00:92:b5:43 STALE
Problem: The ARP table on the server shows the same MAC addresses for the IP addresses of the guest machine (for different Ethernet interfaces).
In the GUEST:
ether 52:54:00:92:b5:43 inet 192.168.100.254 enp7s0
ether 52:54:00:de:34:44 inet 192.168.100.217 enp1s0

In the SERVER(kvm):
192.168.100.254 dev virbr1 lladdr 52:54:00:92:b5:43 STALE
192.168.100.217 dev virbr1 lladdr 52:54:00:92:b5:43 STALE <---!!!!! ???


can anyone advise?

Serg