Alcatel-Lucent 6850-48 Network Guide

Tunneling

Configuring IP

page 24-34

OmniSwitch AOS Release 6 Network Configuration Guide

IPIP tunneling is a method by which an IP packet is encapsulated within another IP packet. The Source 
Address and Destination Address of the outer IP header identifies the endpoints of tunnel. Whereas Source 
Address and Destination Address of the inner IP header identifies the original sender and recipient of the 
packet, respectively. 

Consider the following when configuring the IPIP tunnel interfaces:

• A switch can support up to 127 IPIP tunnel interfaces.

• IPIP tunnel interfaces are included in the maximum number of IP interfaces that are supported on the 

switch. 

The diagram below illustrates how packets are forwarded over the tunnel.

In the above diagram, IP packets flowing from the private IP network 50.0.0.0 to the private IP network 
40.0.0.0 are encapsulated by the tunneling protocol at switch A and forwarded to switch B. Intermediate 
switches route the packets using addresses in the delivery protocol header. Switch B extracts the original 
payload and routes it to the appropriate destination in the 40.0.0.0 network. 

The tunnel interface is identified as being up when all of the following are satisfied:

• Both source and destination addresses are assigned.

• The source address of the tunnel is one of the switch's IP interface addresses that is

 

either a VLAN or 

Loopback0 interface.