Pi-hole HA and LXC

Hi all,
This is probably off Turris topic , but maybe someone can help me out.
I’m using a Pi-hole in an LXC container on Turris (192.168.1.21 and VIP 192.168.1.15). But I would like to start using second Pi-hole server (192.168.1.22) in HA (High Availability) & in-sync. For this I found great manual gravity-sync . This sync is working great for me.
Second Pi-hole is running on mi RaspberryPi 4 (192.168.1.20) also in LXC container.
But here starting my problems.
To keep LXC container in same IP range like my home network I used followed manual for configuration of LXC container: LXC containers on host’s lan
There is no issue with main Pi-hole server running on Turris.
After failover I’m able open pihole GUI on second server true IP 192.168.1.22 but not via VIP 192.168.1.15 and name resolving of web pages is not working (VIP is used like DNS IP).
I’m not so familiar with networking but I expecting that issue is between RaspberryPi and LXC container (traffic is not forwarding correctly, some ports are not opened,…).
Network configuration of RaspberryPi server:

root@raspberrypi:~# arp -a
? (192.168.1.22) at 00:26:5e:11:c1:83 [ether] on veth0
? (192.168.1.1) at 04:f0:21:c3:23:c5 [ether] on eth0
? (192.168.1.15) at 00:26:5e:11:c1:83 [ether] on veth0
? (192.168.1.15) at 32:65:a3:7a:91:ec [ether] on eth0
? (192.168.1.21) at 32:65:a3:7a:91:ec [ether] on eth0
? (192.168.1.22) at <from_interface> PERM PUB on eth0

root@raspberrypi:~# ip route
default via 192.168.1.1 dev eth0 proto static metric 100
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.20 metric 100
192.168.1.22 dev veth0 scope link

LXC network config:

root@Pihole2:~# arp -a
? (192.168.1.20) at fe:30:e3:9b:d5:d0 [ether] on eth0
? (192.168.1.21) at on eth0

root@Pihole2:~# ip route
default via 192.168.1.20 dev eth0
192.168.1.20 dev eth0 scope link

A possible simple question is how to set up LXC container in Raspberry Pi to use like second Pi-hole server?