• Tunneling is an internetworking strategy that is used when source and destination networks of same type are connected through a network of different type.
• In such a case, the packet from one network reaches the other network via different kind pf network that interconnects them.
• To understand tunneling, let an Ethernet is to be connected to another Ethernet via a WAN.
• The IP packets are to be sent from host 1 of Ethernet 1 to host 2 of Ethernet 2 via a WAN.
• To send an IP packet to host 2, host 1 constructs the packet containing the IP address of host 2.
• It then inserts this packet into an Ethernet frame. This frame is addressed to the multi-protocol router M1 and is placed on Ethernet.
• When this packet reaches, multiprotocol router MI, it removes the IP packet and insert it in the payload field of the WAN network layer packet.
• This WAN network layer packet is then addressed to multi-protocol router M2.
• When this packet reaches M2, it removes the IP packet and inserts it into the Ethernet frame and sends it to host 2.
• In the above process, IP packets do not have to deal with WAN, they just travel from one end 0f the tunnel to the other end. The host 1 and host 2 on two Ethernet also do not have to deal with WAN.
• The multi-protocol routers M1 & M2 understand about IP and WAN packets.
Dinesh Thakur holds an B.C.A, MCDBA, MCSD certifications. Dinesh authors the hugely popular