how to config linux using wireguard to connect 3 network ABC using B and bridge then A can access B and C

To configure Linux using WireGuard to connect three networks A, B, and C, with B acting as a bridge, follow these steps:

Install WireGuard on all three Linux systems (A, B, C) if not already installed.
Configure WireGuard on each system by creating a configuration file using the following format:

[Interface]
PrivateKey = <Private Key>
Address = <IP Address/Subnet>
ListenPort = <Port>

[Peer]
PublicKey = <Public Key of the other system>
AllowedIPs = <IP Address/Subnet of the other system>
Endpoint = <Public IP Address:Port of the other system>

Replace <Private Key> and <Public Key> with the private and public keys generated for each system. Set <IP Address/Subnet> according to the network requirements. <Port> is the port number you want to use for WireGuard communication.

On system B, enable IP forwarding by editing /etc/sysctl.conf and uncommenting the line net.ipv4.ip_forward=1 or by running the command sysctl -w net.ipv4.ip_forward=1.
Configure network routing on system B by adding the following rules to the iptables:

iptables -A FORWARD -i wg0 -j ACCEPT
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

Replace wg0 with the appropriate WireGuard interface name, and eth0 with the physical network interface connected to network A.

Start the WireGuard service on all three systems using the command wg-quick up <config-file-name>.
Verify the connection by pinging the IP addresses of network B and C from system A.

By following these steps, you should be able to configure Linux using WireGuard to connect the three networks A, B, and C, allowing network A to access networks B and C