Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 125)

Syntax: [no] tunnel path-mtu-discovery disable
Changing the age timer for PMTUD
By default, when PMTUD is enabled on a tunnel interface, the path MTU is reset to its original value
every 10 minutes. If desired, you can change the reset time (default age timer) to a value of up to 30
minutes. To do so, enter a command such as the following on the GRE tunnel interface.
device(config-tnif-1)# tunnel path-mtu-discovery age-timer 20
This command configures the device to wait for 20 minutes before resetting the path MTU to its original
value.
Syntax:[no] tunnel path-mtu-discovery { age-timer minutes | infinite }
For minutes , enter a value from 10 to 30.
Enter infinite to disable the timer.
Clearing the PMTUD dynamic value
To reset a dynamically-configured MTU on a tunnel Interface back to the configured value, enter the
following command.
device(config)# clear ip tunnel pmtud 1
Syntax: clear ip tunnel pmtud tunnel-ID
The tunnel-ID variable is a valid tunnel number or name.
Viewing PMTUD configuration details
Use the show interface tunnel command to view the PMTUD configuration 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 115. To view information about multicast protocols and GRE tunnel-
specific information, refer to Displaying multicast protocols and GRE tunneling information on page
130.
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 differs from GRE tunnels that support
unicast traffic only. For unicast traffic, multiple GRE tunnels can use the same tunnel loopback port for
traffic.
Enabling IPv4 multicast routing over a GRE tunnel
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