TMS zl Management and Configuration Guide ST.1.2.100916

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Virtual Private Networks
Configure a GRE Tunnel
Note The TMS zl Module’s GRE functionality may not properly detect GRE
keepalives if a non-TMS endpoint specifies GRE options such as a Checksum
or Sequencing. Normal GRE traffic can be received with these options present,
but GRE keepalives with these options are not handled properly. This results
in the GRE tunnel being detected as down by the non-TMS endpoint of
the GRE tunnel. Please note that the TMS zl Module does not currently include
GRE options such as these, so they cannot be configured for transmission
of GRE traffic from the TMS zl Module.
Also note that some GRE implementations allow for a key parameter to be
specified, but the TMS zl Module does not support this parameter. If a GRE
implementation has the key parameter specified, normal GRE traffic as well
as keepalive traffic will not pass.
12. Click OK.
The tunnel is now displayed in the VPN > GRE > GRE Tunnels window.
Figure 7-159. VPN > GRE Window (Tunnel Added)
13. Click Save.
If you want, repeat these steps to create a redundant tunnel.
Verify that a Route to the Remote Tunnel Gateway
Exists
To establish the GRE tunnel, the TMS zl Module requires a route to the tunnel’s
destination address (indicated by 3 in the example figure). The route can be
to the specific address or any network that includes that address. The route
can be a static route or a route discovered with a routing protocol. It can even
be a default route, if the default gateway knows how to reach the remote
tunnel gateway. The forwarding interface for the route to the tunnel destina-
tion must never be the tunnel interface (if it is, recursive routing will shut the
tunnel down).