Conguration tasks for GRE tunnels
Perform the conguration tasks in the order listed.
TABLE 16 Conguration tasks for GRE tunnels
Conguration tasks Default behavior
Required tasks
Create a tunnel interface. Not assigned
Congure the source address or source interface for the tunnel interface. Not assigned
Congure the destination address of the tunnel interface. Not assigned
Enable GRE encapsulation on the tunnel interface.
NOTE
Step 4 must be performed before step 6.
Disabled
If packets need to be terminated in hardware, congure a tunnel loopback
port for the tunnel interface.
NOTE
Step 5 is not applicable to FCX devices.
Not assigned
Congure an IP address for the tunnel interface. Not assigned
If a route to the tunnel destination does not already exist, create a static
route and specify that the route is through the tunnel interface.
Not assigned
Optional tasks
Change the maximum transmission unit (MTU) value for the tunnel
interface.
1476 bytes or
9192 bytes (jumbo mode)
Change the number of GRE tunnels supported on the device. Support for 32 GRE tunnels
Enable and congure GRE link keepalive on the tunnel interface. Disabled
Change the Path MTU Discovery (PMTUD) conguration on the GRE
tunnel interface.
Enabled
Enable support for IPv4 multicast routing. Disabled
The following features are also supported on GRE tunnel interfaces:
• Naming the tunnel interface (CLI command port-name ).
• Changing the Maximum Transmission Unit (MTU) (CLI command ip mtu ).
• Increasing the cost of routes learned on the port (CLI command ip metric ).
After conguring GRE tunnels, you can view the GRE conguration and observe the routes that use GRE tunnels.
Creating a tunnel interface
To create a tunnel interface, enter the following command at the Global CONFIG level of the CLI.
device(config)# interface tunnel 1
device(config-tnif-1)#
Syntax: [no] interface tunnel tunnel-number
The tunnel-number is a numerical value that
identies the tunnel being congured.
IPv4 point-to-point GRE tunnels
FastIron Ethernet Switch Layer 3 Routing
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