Qfyilyi

So i take internet from my Raspberry pi 3b+ running Raspbian Stretch Kernel version:4.14, wlan0 and i just create a network bridge to give internet to ethernet adaptor witch will give ip adresses by dhcp when i plug a new computer to it. so i did it and it works but when i try to ping from my main computer witch is on 192.168.1.0/24 to 192.168.2.0/24 network i can't but when i try to ping from 192.168.2.0/24 network to 192.168.1.0/24 i can.Why is that? i want to be able to reach 192.168.2.xxx cuz i want to host a webserver there .Help..

I tried to bridge like this :

sudo apt-get install dnsmasq



sudo nano /etc/dhcpcd.conf:

interface eth0

static ip_address=192.168.2.1/24 

static routers=192.168.2.0



sudo nano /etc/network/interfaces:

 auto eth0

allow-hotplug eth0 

iface eth0 inet static

    address 192.168.2.1 

    netmask 255.255.255.0

    network 192.168.2.0 

    broadcast 192.168.2.255



auto wlan0

allow-hotplug wlan0 

iface wlan0 inet static 

    address 192.168.1.10 

    gateway 192.168.1.1 

    netmask 255.255.255.0 

    network 192.168.1.0 

    broadcast 192.168.1.255 

wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf



sudo service dhcpcd restart



sudo nano /etc/dnsmasq.conf:

interface=eth0 # Use interface eth0 listen-address=192.168.2.1 # Specify the address to listen on bind-interfaces # Bind to the interface 

server=8.8.8.8 # Use Google DNS

domain-needed # Don't forward short names

bogus-priv # Drop the non-routed address spaces. 

dhcp-range=192.168.2.10,192.168.2.20,12h # IP range and lease time



sudo nano /etc/sysctl.conf:

net.ipv4.ip_forward=1 





sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"

sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE 

sudo iptables -A FORWARD -i wlan0 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT 

sudo iptables -A FORWARD -i eth0 -o wlan0 -j ACCEPT`

sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"



sudo service dnsmasq start

So from what I can tell your current network setup is:

• One private network of 192.168.1.0/24, let's call this net1


• A separate private network of 192.168.2.0/24, let's call this net2

Now, net1 is not a subset of net2. They're actually two separate networks and you'd need to route between them.

It looks like:

• Your "main" computer, let's call it pcA, is on net1


• Your "new" computer, let's call it pcB, is on net2


• You have a Raspberry Pi that has an address on both net1 and net2.


• You have the Pi acting as a gateway for net2, and performing NAT such that hosts on net2 (including pcB) can access net1 (and therefore the internet via net1). This is effectively what your typical home NAT router does.
  
  
  
  
  • This would explain why you can access net1 hosts from net2 but not the other way around.
  
  
  
  

Given that setup, you have a few options:

• You can treat this as any other NAT router (layer 3) and perform port forwarding. In other words, you can forward a port from the Pi's net1 address towards a specific port on a net2 host. For example, assuming the Pi has a net1 address of 192.168.1.10 and pcB has a net2 address of 192.168.2.55, you could forward 192.168.1.10:80 to 192.168.2.55:80. Then, you can access port 80 on pcB from net1 hosts by accessing the Pi's port 80 (192.168.1.10:80).




• You could bridge (layer 2) the two interfaces on the Pi. This would mean everything is on net1, and net2 does not exist. Everything would be in the 192.168.1.0/24 space and can freely access each other. This would mean your Pi is no longer acting as a router, and you should abandon NAT and disable DHCP and DNS services on the Pi. Everything on the eth0 interface of the Pi would be assigned a net1 address via the DHCP server of net1, via the bridged connection.



• 
  

  You could continue to have the two separate networks (layer 3), and continue using NAT for external hosts, but properly route between your internal networks. To do this, you have two options:

  
  
  
  
  
  • Currently, your net1 hosts will all hit their default gateway for anything not on the same network. You can continue doing this, and configure the default gateway (probably your generic home router) to forward any net2 destinations to the Pi's net1 address.
  
  
  • You could individually configure each net1 host with a static route for net2 destinations to go via the Pi's net1 address. This is a bit more configuration work, but will be faster as packets do not have to be routed through net1's gateway.
  
  
  
  

  With either of these, you should configure the Pi to not apply NAT to requests with a net1 destination; these should be forwarded without translation.

  
  

Port forwarding is the easiest option with your current setup. But I'd recommend either bridging (if you don't actually need the extra network, this is the cleanest solution) or routing (if you actually need an extra network, e.g. for firewalling purposes) without NAT, as they will give you full access to hosts without having to forward each port individually.