USER MANUAL
GWR Router Series
32
Settings – VPN Settings
Virtual private network (VPN) is a communications network tunneled through another network
and dedicated to a specific network. One common application of VPN is secure communication through the
public Internet, but a VPN need not have explicit security features, such as authentication or content
encryption. VPNs, for example, can be used to separate the traffic of different user communities over an
underlying network with strong security features.
A VPN may have best-effort performance, or may have a defined Service Level Agreement (SLA)
between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex
than point-to-point. The distinguishing characteristics of VPNs are not security or performance, but that
they overlay other network(s) to provide a certain functionality that is meaningful to a user community.
Generic Routing Encapsulation (GRE)
Originally developed by Cisco, generic routing encapsulation (GRE) is now a standard, defined in
RFC 1701, RFC 1702, and RFC 2784. GRE is a tunneling protocol used to transport packets from one network
through another network.
If this sounds like a virtual private network (VPN) to you, that’s because it theoretically is:
Technically, a GRE tunnel is a type of a VPN — but it isn’t a secure tunneling method. However, you can
encrypt GRE with an encryption protocol such as IPSec to form a secure VPN. In fact, the point-to-point
tunneling protocol (PPTP) actually uses GRE to create VPN tunnels. For example, if you configure Microsoft
VPN tunnels, by default, you use PPTP, which uses GRE.
Solution where you can use GRE protocol:
•
You need to encrypt multicast traffic. GRE tunnels can carry multicast packets — just like real
network interfaces — as opposed to using IPSec by itself, which can’t encrypt multicast traffic. Some
examples of multicast traffic are OSPF, EIGRP. Also, a number of video, VoIP, and streaming music
applications use multicast.
•
You have a protocol that isn’
t routable, such as NetBIOS or non
-IP traffic over an IP network. You
could use GRE to tunnel IPX/AppleTalk through an IP network.
•
You need to connect two similar networks connected by a different network with different IP
addressing.
Click
VPN Settings
Tab, to open the VPN configuration screen. In the Figure 16 you can see
screenshot of
GRE
Tab configuration menu.
VPN Settings / GRE Tunneling Parameters
Label
Description
Enable
This check box allows you to activate/deactivate VPN/GRE traffic.
Local Tunnel Address
This field specifies IP address of virtual tunnel interface.
Local Tunnel Netmask
This field specifies the IP netmask address of virtual tunnel. This field is
unchangeable, always 255.255.255.252
Tunnel Source
This field specifies IP address or hostname of tunnel source.
Tunnel Destination
This field specifies IP address or hostname of tunnel destination.
Interface
This field specifies GRE interface. This field gets from the GWR Router.
KeepAlive Enable
Check for keepalive enable.
Period
Defines the time interval (in seconds) between transmitted keepalive packets.
Enter a number from 3 to 60 seconds.
Retries
Defines the number of times retry after failed keepalives before determining that
the tunnel endpoint is down. Enter a number from 1 to 10 times.
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