GRE tunnels
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GRE
TUNNELS
GRE
TUNNEL CONFIGURATION
GRE is the abbreviation of
Generic Routing Encapsulation
and it is a standard encapsulation used
to establish tunnels between interfaces of two systems, connected either directly or remotely.
The activation of a GRE tunnel requires the configuration of the following parameters:
the name of the GRE tunnel interface
the IP address of the physical interface on which the tunnel will be activated (
tunnel-
source
)
the IP address of the remote physical interface towards which the tunnel will be terminated
(
tunnel-destination
)
the local IP address to assign to the tunnel (
tunnel-address
)
the remote IP address to assign to the tunnel (
tunnel-peer
)
Optionally, for each tunnel configured, it is possible to set the following parameters:
MTU (Max Transfer Unit)
TTL (Time to Live)
Multicast (enable multicast transmission)
keep-alive
: it is possible to enable
keep-alive
functionality by configuring the
parameters
keepalive-intval
(interval for sending
keep-alive
packets) and keepalive-
retries (maximum number of lost
keep-alive
packets before the tunnel interface is
terminated)
Starting from the 5.4.5-4 software version, the maximum number of tunnels configurable is 256; le
previous versions have only 8. The syntax is:
set gre tunnel X <options>
where
x
can be 0 to 255
Below you find the main configuration commands, where it is used the notation
set gre tunnel 0 <options>
but the same commands are applied with:
set gre tunnel 0 <options>
set gre tunnel 1 <options>
....
set gre tunnel X <options>
In order to establish the name of the network interface associated with the tunnel the following
command is used:
set gre tunnel 0 name <name>