Introduction

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Introduction

GRE (Generic Routing Encapsulation) is a tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links over an Internet Protocol network. The GRE Tunnel can be configured between any two devices that are compatible with this protocol.

  • From the point of view of the traffic transferred, the GRE tunnel is one hop.

  • There are 2 modes of GRE operation: TUN (Tunnel mode) or TAP (L2 transparent connection) with SW bridge. Implementation within RipEX only covers the TUN mode.

  • Packets passing through the GRE tunnel are not protected against loss and are not encrypted.

  • The GRE tunnel neither establishes nor maintains a connection with the peer. The GRE tunnel is created regardless of peer status (peer need not exist at all).

  • The GRE tunnel has its own IP address and mask. Network defined by this address and mask contains only 2 nodes – each end of the tunnel.

  • As the GRE tunnel adds an additional header, a lower MTU is set (1476 B) to prevent GRE packet fragmentation. Incoming packets may be fragmented within the GRE interface.

NOTE:
Packet acknowledgment and encryption (AES256) can be configured on the Radio channel. Both options are independent of GRE tunnels and apply to all the radio traffic.

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