Copyright © 2006 – STM Norway AS
Publication no. 101557, Rev. T, November 3
th
, 2006
Page 66
15.2 Generic Routing Encapsulation (GRE) and IP Tunnelling
The STM SatLink Terminal supports configuration of one IP tunnel from its DVB interface with Generic
Routing Encapsulation (GRE) as specified in RFC 2784. Only the tunnel termination interface IP address,
tunnel logical destination IP address and subnet mask need to be specified since the tunnel will always be
set up from the DVB interface.
Example:
#ip gre add 192.168.1.0 255.255.255.0 10.20.1.1
Will set up a tunnel on the DVB interface to the IP address 10.20.1.1 for the subnet
192.168.1.0/255.255.255.0.
To verify that a GRE tunnel and a GRE interface have been created, use the CLI command
ip gre
show.
Example:
# ip gre show
GRE Tunnel Interfaces:
----------------------
If Tunnel Local Address Tunnel Remote Address
4 192.168.255.2 10.20.1.1
Interface number 4 has been allocated for the GRE interface. Use the CLI command
ip show
to verify
that a new IP interface has been created and that 2 new entries have been added to the IP routing table.
The first entry in order to route traffic with destination address equal to the tunnel remote address to the
DVB interface. The second entry to route traffic with destination address belonging to the tunnel remote
local subnet to the GRE interface.
# ip show
Interfaces
If IPAddress SubnetMask BroadCastAddr MTU Alias AdminStatus
1 10.10.20.115 255.255.255.248 10.10.20.119 1500 eth0 1
2 N/A N/A N/A 4074 air0 1
3 192.168.255.2 255.255.255.0 192.168.255.255 4074 dvb0 1
4 N/A N/A 255.255.255.255 4074 gre0 1
Interface Statistics
------------- Input ----------------- ------------- Output ----------------
If UCast NUCast Disc Octets UCast NUCast Disc Octets
1 14 98 43 13737 18 29 0 4984
2 0 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0 0
Routing Table
DestMask RouteMask NextHop If
0.0.0.0 0.0.0.0 0.0.0.0 3
10.10.20.112 255.255.255.248 0.0.0.0 1
10.20.1.1 255.255.255.255 0.0.0.0 3
192.168.1.0 255.255.255.0 0.0.0.0 4
192.168.255.0 255.255.255.0 0.0.0.0 3
