## Name

nexp-gre — Generic Routing Encapsulation (GRE) support for Network Expect

## Synopsis

PDU definition:

`gre` ( [ `proto`=`num`,] [ `cksum` ] )

## PDU Definition

The following parameters allow you to define the different parts of a GRE protocol data unit (PDU) in Network Expect:

`proto` = `NUMSPEC`

  Specifies the value of the Protocol field in the GRE header. Default: Ethertype of tunneled protocol if known; zero if unknown.

`cksum`

  Sets the checksum flag of the GRE PDU and instructs Network Expect to compute and store the checksum in the GRE header.

## PDU Decoding

The current version of Network Expect does not support the decoding of received GRE PDUs into the Tcl array variable gre.

## Examples

1. A simple GRE packet.

       ip(dst = www.netexpect.org)/gre()

2. A GRE packet containing a checksum:

       ip(dst = www.netexpect.org)/gre(cksum)

3. A GRE packet containing an IP packet destined to 10.1.1.1:

       ip(dst = www.netexpect.org)/gre()/ip(dst = 10.1.1.1)

4. A GRE packet with a specific protocol field and raw payload:

       ip(dst = www.netexpect.org)/gre(proto = 0x4141)/raw('AA')

## VERSION

This man page is correct for version 1.0 of Network Expect.

## SEE ALSO

nexp(1), nexp-numspec(5), RFC 2784

## AUTHOR

Generic Routing Encapsulation support for Network Expect was written by Eloy Paris <peloy@netexpect.org>.

This man page was written by Tim Sammut <tsammut@cisco.com>.