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26-6
User Guide for Cisco Security Manager 4.4
OL-28826-01
Chapter 26 GRE and DM VPNs
GRE and Dynamic GRE VPNs
Related Topics
• Understanding IKE, page 25-5
• Understanding GRE, page 26-2
• Prerequisites for Successful Configuration of GRE, page 26-3
• Advantages of IPsec Tunneling with GRE, page 26-3
Configuring GRE Modes for GRE or GRE Dynamic IP VPNs
Use the GRE Modes policy to define the routing and tunnel parameters for IPsec tunneling in a GRE or
GRE Dynamic IP VPN.
To open the GRE Modes policy:
• (Site-to-Site VPN Manager Window, page 24-18) Select an IPsec/GRE or GRE Dynamic IP
topology, then select GRE Modes from the policies list.
• (Policy view) Select Site-to-Site VPN > GRE Modes, and create a new policy or select an existing
policy. Then, select either IPsec/GRE or Dynamic GRE from the GRE Method list.
The following table describes the elements on the GRE Modes page for configuring IPsec tunneling with
GRE or GRE Dynamic IP.
Note When configuring a GRE routing policy, Security Manager adds a routing protocol to all the devices in
the secured IGP, on deployment. If you want to maintain this secured IGP, you must create a router
platform policy (on each member device) using the same routing protocol and autonomous system (or
process ID) number as defined in the GRE Modes policy.
Table 26-1 GRE Modes Page for GRE or GRE Dynamic IP VPNs
Element Description
Routing Parameters Tab
Routing Protocol Select the required dynamic routing protocol (EIGRP, OSPF, or
RIPv2,) or static route to be used for GRE or GRE Dynamic IP.
The default routing protocol is EIGRP.
For more information about configuring these protocols, see
Prerequisites for Successful Configuration of GRE, page 26-3.
AS Number
(EIGRP only.)
The number that is used to identify the autonomous system (AS) area
to which the EIGRP packet belongs. The range is 1-65535. The default
is 110.
An autonomous system (AS) is a collection of networks that share a
common routing strategy. An AS can be divided into a number of areas,
which are groups of contiguous networks and attached hosts. Routers
with multiple interfaces can participate in multiple areas. An AS ID
identifies the area to which the packet belongs. All EIGRP packets are
associated with a single area, so all devices must have the same AS
number.
Hello Interval
(EIGRP only.)
The interval between hello packets sent on the interface, between 1 and
65535 seconds. The default is 5 seconds.