some problems with GRE Tunnel



i can`t understanding these configurations

1- if we are using ip address under tunnel interface , then why we need tunnel source s0/0 configuration?

by default source ip address of the packet go threw must be source address , so why we need to change this address by using tunnel source command?

2- if new packet is created into the original ip packet  before it sent out of the tunnel interface , then it`s P2P interface , why we need Destinatio0n ip address command?


3- ccna certification book told us that tunnel interfaces must be into same ip address range, then why we need this if these two logical interfaces are P2P interfaces like serial


if anyone have good link about GRE that explaining these commands , please share it


  • MartinlMartinl ✭✭✭

    your pciture uses "reverse" ip range.  public ip range is used for underlay link. Private should be overlay (tunnel ip).  tunnel source tells which interface is used to build tunnel. tunnel source ip and tunnel destination ip should be on same network range.

    there are static and dynamic gre tunnels; also p2p or p2mp.  u have static one , p2p.


    INE wb for CCIE RS has good explanations and labs for gre tunnels. also videos are preety good, must have !!

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