To Configure port forwarding on ‘cisco’ routers is comparable to the configuration of static NAT. It’s a static NAT translation having a specific TCP or UDP port number.
The figure above shows a good example to configure port forwarding using ‘cisco’ IOS instructions on router R2, 192.168.11.100 may be the inside local IPv4 address from the webserver.
The listening port from the webserver is port 80. The administrator really wants to access this internal webserver from your exterior network while using global Ip 202.128.54.1 a globally unique public IPv4 address.
It’s the address from the g0/1 interface of R2. The worldwide port is configured as 8080 which is the destination port used, combined with the global IPv4 address of 202.128.54.1 to gain access to the interior webserver. The command syntax to configure port forwarding may be the following:
Router(config)#Ip nat inside source udp) local-ip local-port global-ip global-port [extendable]
TCP or UP – This parameter showing the port is associated with TCP or UDP
Local-IP – This is actually the IPv4 address towards the host within the local network.
Local Port- This is actually the port from the local host in a variety of 1-65535.
Global-IP – This is actually the IPv4 address from the inside host globally unique. The outdoors clients uses this IP to achieve the interior host.
Global-port – This is actually the global TCP/UDP port within the vary from 1-65535. This is actually the port number the outdoors client uses to achieve the interior server.
Extendable – The extendable choice is applied instantly. This keyword enables the consumer to configure ambiguous static translation. It extends the static translation to several port if required
When you want to make use of a port apart from well-known ports, the customer must specify the main harbour number within the web request. Such as the simple static or dynamic NAT configuration, we ought to configure port forwarding for the inside and outdoors NAT interfaces. To configure port forwarding on R1, the instructions are:
- R2(config)#ip nat inside source static tcp 192.168.11.100 80 202.128.54.1 8080
- R2(config)interface g0/
- R2(config-if)ip nat inside
- R2(config-if)exit
- R2(config)interface s0//.101
- R2(config-if)ip nat outdoors
Port forwarding verification
Much like static NAT verification we are able to also verify the main harbour forwarding configuration using, the “show ip nat translations” command. The below image illustrates the creation of this command.
Once the router receives the packet using the inside global IPv4 address of 202.128.54.1 including TCP destination port 8080, the lookup the NAT table while using destination IPv4 address and destination port because the key and translates the address towards the inside local address of host 192.168.11.100 such as the destination port 80. R2 then forwards the packet towards the webserver. When webserver replies the packets to the customer, this method is reversed.
