How to access from a local VPN network to a laptop behind a router?

Question

linux

There is an ASUS RT-N14U router with firmware from padavan (ver. 3.4.3.9 base), a laptop is connected to it via ethernet. The router accesses the Internet via a USB modem, then over this it connects to the server via VPN. A PC is also connected to the server via VPN (in another place). It is necessary to make it so that the PC can access the laptop on a specific port. A PC (VPN 192.168.0.11) when accessing port 80 (VPN 192.168.0.100:80) opens the router admin panel, port forwarding to the laptop (port 80 at 192.168.3.20:27100) did not give results, the router admin panel also opens. Port 27100 is open on the laptop, I hung up a web server for the test, it works on LAN. Advise what routes to create, what ports to forward?
Laptop lan 192.168.3.20
Router lan 192.168.3.1
Router usb modem 192.168.1.1
Router vpn 192.168.0.100
PC vpn 192.168.0.11
Command results:
router ifconfig -a

apcli0    Link encap:Ethernet  HWaddr 34:97:F6:69:14:BE
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
 
br0       Link encap:Ethernet  HWaddr 34:97:F6:69:14:BC
          inet addr:192.168.3.1  Bcast:192.168.3.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5700 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6167 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:645065 (629.9 KiB)  TX bytes:4350332 (4.1 MiB)
 
eth2      Link encap:Ethernet  HWaddr 34:97:F6:69:14:BC
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5813 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6390 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:761458 (743.6 KiB)  TX bytes:4400355 (4.1 MiB)
          Interrupt:3
 
eth2.1    Link encap:Ethernet  HWaddr 34:97:F6:69:14:BC
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5813 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6378 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:656824 (641.4 KiB)  TX bytes:4361262 (4.1 MiB)
 
eth2.2    Link encap:Ethernet  HWaddr 34:97:F6:69:14:BF
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
 
lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:8 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:681 (681.0 B)  TX bytes:681 (681.0 B)
 
ppp5      Link encap:Point-to-Point Protocol
          inet addr:192.168.0.100  P-t-P:192.168.0.1  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1450  Metric:1
          RX packets:42 errors:0 dropped:0 overruns:0 frame:0
          TX packets:25 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:2477 (2.4 KiB)  TX bytes:3687 (3.6 KiB)
 
ra0       Link encap:Ethernet  HWaddr 34:97:F6:69:14:BC
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:4
 
ra1       Link encap:Ethernet  HWaddr 34:97:F6:69:14:BD
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
 
sit0      Link encap:IPv6-in-IPv4
          NOARP  MTU:1480  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
 
wds0      Link encap:Ethernet  HWaddr 34:97:F6:69:14:BC
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
 
wds1      Link encap:Ethernet  HWaddr 34:97:F6:69:14:BC
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
 
wds2      Link encap:Ethernet  HWaddr 34:97:F6:69:14:BC
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
 
wds3      Link encap:Ethernet  HWaddr 34:97:F6:69:14:BC
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
 
weth0     Link encap:Ethernet  HWaddr 58:2C:80:13:92:63
          inet addr:192.168.1.100  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:786 errors:0 dropped:0 overruns:0 frame:0
          TX packets:654 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:217838 (212.7 KiB)  TX bytes:115567 (112.8 KiB)

route router

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         192.168.1.1     0.0.0.0         UG    1      0        0 weth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
192.168.0.0     192.168.0.1     255.255.255.0   UG    0      0        0 ppp5
192.168.0.1     *               255.255.255.255 UH    0      0        0 ppp5
192.168.1.0     *               255.255.255.0   U     0      0        0 weth0
192.168.3.0     *               255.255.255.0   U     0      0        0 br0

iptables router -L -n -v

Chain INPUT (policy DROP 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination
  173 18852 ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            state RELATED,ESTABLISHED
   24  1432 ACCEPT     all  --  br0    *       0.0.0.0/0            0.0.0.0/0
    0     0 ACCEPT     all  --  lo     *       0.0.0.0/0            0.0.0.0/0
    0     0 DROP       all  --  *      *       0.0.0.0/0            0.0.0.0/0            state INVALID
    0     0 ACCEPT     all  --  ppp5   *       0.0.0.0/0            0.0.0.0/0
    0     0 ACCEPT     udp  --  *      *       0.0.0.0/0            0.0.0.0/0            udp spt:67 dpt:68
    0     0 ACCEPT     icmp --  *      *       0.0.0.0/0            0.0.0.0/0            icmp !type 8
 
Chain FORWARD (policy DROP 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination
    0     0 ACCEPT     all  --  br0    br0     0.0.0.0/0            0.0.0.0/0
    0     0 TCPMSS     tcp  --  *      ppp5    0.0.0.0/0            0.0.0.0/0            tcp flags:0x06/0x02 TCPMSS clamp to PMTU
   14  3386 ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            state RELATED,ESTABLISHED
    0     0 DROP       all  --  *      *       0.0.0.0/0            0.0.0.0/0            state INVALID
    0     0 ACCEPT     all  --  br0    *       0.0.0.0/0            0.0.0.0/0
    0     0 ACCEPT     all  --  ppp5   *       0.0.0.0/0            0.0.0.0/0
    0     0 ACCEPT     tcp  --  *      *       0.0.0.0/0            192.168.3.20         tcp dpt:27100
    0     0 upnp       all  --  *      *       0.0.0.0/0            0.0.0.0/0
 
Chain OUTPUT (policy ACCEPT 226 packets, 217K bytes)
 pkts bytes target     prot opt in     out     source               destination
 
Chain bfplimit (0 references)
 pkts bytes target     prot opt in     out     source               destination
 
Chain upnp (1 references)
 pkts bytes target     prot opt in     out     source               destination
 
Chain vpnlist (0 references)
 pkts bytes target     prot opt in     out     source               destination

from the laptop (192.168.3.1) to 192.168.0.1 the ping goes.
Tracing to 192.168.0.1:
192.168.3.1 -> 192.168.0.1
Tracing to 192.168.0.11:
192.168.3.1 -> 192.168.0.1 -> Timed out...

Answer 1

Either forward port 27100 or remove the admin panel from port 80 to some other one, for example. 8080.