Enlarging the Operation Scope of a Network with a Hop Limit

You can set up a GRE tunnel between two devices on a network to hide the hops between them. If a network using IP protocol limits the hop count to 255 and the hop count between two PCs is more than 255, they cannot communicate with each other. Using a GRE tunnel can negate this problem and enlarge the network operation scope, as shown in Figure 1.

Figure 1 Enlarging the network operation scope

For example, the Routing Information Protocol (RIP) protocol defines an unreachable route when the hop count reaches 16. You can configure a GRE tunnel between two devices to reduce the hop count of the RIP route passing through the GRE tunnel to less than 16 and thereby make this route reachable.