Viewing PMTUD conguration details
Use the show interface tunnel command to view the PMTUD conguration and to determine whether PMTUD has reduced the size of
the MTU.
Enabling IPv4 multicast routing over a GRE tunnel
This section describes how to enable IPv4 multicast protocols, PIM Sparse (PIM-SM) and PIM Dense (PIM-DM), on a GRE tunnel.
Perform the procedures in this section after completing the required tasks in Enabling IPv4 multicast routing over a GRE tunnel.
For an overview of multicast routing support over a GRE tunnel, refer to Support for IPv4 multicast routing over GRE tunnels on page
105. To view information about multicast protocols and GRE tunnel-specic information, refer to Displaying multicast protocols and
GRE tunneling information on page 119.
NOTE
For the SX-FI624C, SX-FI624P, SX-FI624HF, and the SX-FI62XG modules, each PIM-enabled tunnel interface must have a
dedicated tunnel loopback port. This diers from GRE tunnels that support unicast trac only. For unicast trac, multiple GRE
tunnels can use the same tunnel loopback port for trac.
Enabling PIM-SM on a GRE tunnel
To enable PIM-SM on a GRE tunnel interface, enter commands such as the following:
device(config)# interface tunnel 10
device(config-tnif-10)# ip pim-sparse
Syntax: [no] ip pim-sparse
Use the no form of the command to disable PIM-SM on the tunnel interface.
Enabling PIM-DM on a GRE tunnel interface
To enable PIM-DM on a GRE tunnel interface, enter commands such as the following:
device(config)# interface tunnel 10
device(config-tnif-10)# ip pim
Syntax: [no] ip pim
Use the no form of the command to disable PIM-DM on the tunnel interface.
Example point-to-point GRE tunnel
conguration
A GRE Tunnel is congured between FastIron A and device B. Trac between networks 10.10.1.0/24 and 10.10.2.0/24 is
encapsulated in a GRE packet sent through the tunnel on the 10.10.3.0 network, and unpacked and sent to the destination network. A
static route is congured at each Layer 3 switch to go through the tunnel interface to the target network.
IPv4 point-to-point GRE tunnels
FastIron Ethernet Switch Layer 3 Routing
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