Tunnel
Use the Tunnel tab to view, create, edit, and delete GRE tunnels. GRE tunnels encapsulate one network protocol for transfer across another network layer. Within a mixed TCP/IP and OSI network, GRE tunnels tunnel IP traffic over an OSI NE and tunnel OSI traffic over an IP NE.
 
Item
Description
Destination IP
Displays the IP address of the GRE destination CTC or Cisco Transport Manager (CTM) computer.
Destination IP Mask
Displays the IP address subnet mask of the destination CTC or CTM computer.
OSPF Cost
Displays the cost for sending packets across the GRE tunnel. Cost is used by OSPF routers to calculate the shortest path.
Destination NSAP
Displays the destination NE NSAP address. The NSAP Selector (last two NSAP characters) must be 2f (GRE tunnel), or cc (proprietary Cisco tunnel), depending where tunnel type you want to create. The Cisco proprietary tunnel is slightly more efficient than the GRE tunnel because it does not add an encapsulation header for each IP packet, while GRE adds a small header to the packets. The two tunnel types are not compatible. Most Cisco routers support the Cisco tunnel, while only a few support both GRE and Cisco IP tunnels. You generally will create Cisco IP tunnels if you are tunneling between two Cisco routers or between a Cisco router and an ONS node.
Create
Displays the Create GRE Tunnel dialog box where you can create GRE tunnels.
Edit
Displays the Edit GRE Tunnel dialog box to edit the selected GRE tunnel.
Delete
Deletes the selected GRE tunnel.
Help
Displays context-sensitive help.

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