3Com Switch 8800 Family IPsec Module Configuration and Command reference Guide

134 CHAPTER 9: CONFIGURATION OF GRE
n
The destination command sets IP address of actual physical interface. In order to
support dynamic routing protocols, network address of Tunnel interface also
needs configuring.
Assigning Network
Address to Tunnel
Interface
You must assign addresses to the interfaces at the ends of a Tunnel. The assigned
addresses can be private ones but they must belong to the same network
segment.
Perform the following configuration in Tunnel interface view.
By default, network address of Tunnel interface is not configured.
Configuring End-to-End
Verification on Both
Ends of Tunnel
As RFC1701 provisioned, if the Checksum Present bit in GRE header is set to 1,
then the checksum field is present and contains valid information. The sender
calculates the checksum according to GRE header and payload information and
sends the packet containing the checksum information to the peer end. The
receiver calculates the checksum of the received packet and compares it with the
one in the packet. If they are consistent, the packet that may be discarded
otherwise will be further processed.
Checksum can be enabled or disabled on the two ends of a Tunnel as needed. If
checksum is enabled only at the local end, the local end will calculate the
checksum of each transmitted packet but will ignore the checksum of received
packets; on the contrary, if checksum is enabled only at the remote end, the local
end will verify the checksum of each received packet but will ignore the checksum
of transmitted packets.
Perform the following configuration in Tunnel interface view.
By default, end-to-end verification is disabled on both ends of Tunnel.
Setting Identification
Key of Tunnel Interface
RFC1701 provisions that if the Key Present bit in the GRE header of a packet is set
to 1, the Tunnel identification key carried by the packet will be verified between
Tabl e 121 Specify destination address of the Tunnel
Operation Command
Set destination address of the Tunnel destination ip-addr
Delete the destination address of the Tunnel undo destination
Tabl e 122 Assign network address to a Tunnel interface
Operation Command
Assign an IP address to the Tunnel interface ip address ip-addr mask
Delete the IP address of the Tunnel interface undo ip address
Tabl e 123 Enable/disable end-to-end verification on both ends of a Tunnel
Operation Command
Enable end-to-end verification on both ends of the Tunnel gre checksum
Disable end-to-end verification on both ends of the Tunnel undo gre checksum