Routing between two subnets at same interface

[a1ik]

Hello everyone!

I have GPON SFP ONU Stick with telnet at his board.
SFP module connecting me to GPON internet.

Now, i can configurate my SFP module by telnet inside
Proxmox virtual mashine (Win10) connecting to (192.168.1.1)
Win10 have vlan linket to vmbr1 with static IP (192.168.1.4/24)

I need use GPON as default internet and if link down,
i want to use script to reboot SFP module by telnet.
How connect to SFP module direct from (debian/proxmox) CLI?

My setup (Debian/Proxmox) at this moment:
1. vmbr0 geting LAN DHCP IP (192.168.20.20/24) with internet i am using now
2. vmbr1 geting GPON DHCP IP (xxx.xxx.xxx.xxx/20) from provider with internet


# cat /etc/network/interfaces

auto lo
iface lo inet loopback

iface enp7s0 inet manual
# The LAN network interface

iface enp3s0f0 inet manual
# The SFP network interface

auto vmbr0
iface vmbr0 inet dhcp
  bridge-ports enp7s0
  bridge-stp off
  bridge-fd 0
# External LAN

auto vmbr1
iface vmbr1 inet dhcp
  bridge-ports enp3s0f0
  bridge-stp off
  bridge-fd 0
# External SFP

# 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
2: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr0 state UP group default qlen 1000
    link/ether ma:c1:ad:dr:es:s1 brd ff:ff:ff:ff:ff:ff
3: enp3s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master vmbr1 state UP group default qlen 1000
    link/ether ma:c2:ad:dr:es:s2 brd ff:ff:ff:ff:ff:ff
4: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether ma:c3:ad:dr:es:s3 brd ff:ff:ff:ff:ff:ff
    inet 192.168.20.20/24 brd 192.168.20.255 scope global vmbr0
       valid_lft forever preferred_lft forever
5: vmbr1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether ma:c4:ad:dr:es:s4 brd ff:ff:ff:ff:ff:ff
    inet XX.XX.XX.XX/20 brd YY.YY.YY.YY scope global dynamic vmbr1
    valid_lft 271sec preferred_lft 271sec
6: tap100i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr1 state UNKNOWN group default qlen 1000
    link/ether ma:c5:ad:dr:es:s5 brd ff:ff:ff:ff:ff:ff

# ip r

default via 192.168.20.1 dev vmbr0
XX.XX.XX.0/20 dev vmbr1 proto kernel scope link src YY.YY.YY.YY
192.168.20.0/24 dev vmbr0 proto kernel scope link src 192.168.20.20

# tcpdump -i vmbr1 host 192.168.1.1 -n

tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on vmbr1, link-type EN10MB (Ethernet), snapshot length 262144 bytes
23:33:06.713705 IP 192.168.1.4.49669 > 192.168.1.1.23: Flags [S], seq 3119061087, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:33:06.714501 IP 192.168.1.1.23 > 192.168.1.4.49669: Flags [S.], seq 3041700009, ack 3119061088, win 5840, options [mss 1460,nop,nop,sackOK,nop,wscale 2], length 0
23:33:06.714557 IP 192.168.1.4.49669 > 192.168.1.1.23: Flags [.], ack 1, win 1026, length 0
23:33:06.744040 IP 192.168.1.1.23 > 192.168.1.4.49669: Flags [P.], seq 1:16, ack 1, win 1460, length 15 [telnet DO ECHO, DO NAWS, DO LFLOW, WILL ECHO, WILL SUPPRESS GO AHEAD]
23:33:06.744309 IP 192.168.1.4.49669 > 192.168.1.1.23: Flags [P.], seq 1:4, ack 16, win 1026, length 3 [telnet WILL ECHO]
23:33:06.745319 IP 192.168.1.1.23 > 192.168.1.4.49669: Flags [.], ack 4, win 1460, length 0
23:33:06.745435 IP 192.168.1.4.49669 > 192.168.1.1.23: Flags [P.], seq 4:25, ack 16, win 1026, length 21 [telnet WILL NAWS, SB NAWS IS 0x78 0 0x2d SE, WONT LFLOW, DO ECHO, DO SUPPRESS GO AHEAD]
23:33:06.746306 IP 192.168.1.1.23 > 192.168.1.4.49669: Flags [.], ack 25, win 1460, length 0
23:33:06.756548 IP 192.168.1.1.23 > 192.168.1.4.49669: Flags [P.], seq 16:23, ack 25, win 1460, length 7
23:33:06.811750 IP 192.168.1.4.49669 > 192.168.1.1.23: Flags [.], ack 23, win 1026, length 0
^C
10 packets captured
10 packets received by filter
0 packets dropped by kernel

I was trying already with:
1. iptables -A POSTROUTING -s '192.168.1.1' -o vmbr1 -j MASQUERADE no sucess
2. ip route add 192.168.1.1/32 dev vmbr1 no sucess
3. ip route add 192.168.1.1/32 dev enp3s0f0 no sucess