Configuration Guide User guide

FastIron Configuration Guide 1057
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IPv4 point-to-point GRE tunnels
To re-enable PMTUD after it has been disabled, enter the following command:
Brocade(config-tnif-1)# no tunnel path-mtu-discovery disable
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.
Brocade(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.
Brocade(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. For details about the show interface tunnel
command, refer to “Displaying GRE tunneling information” on page 1059.
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 Table 179 on page 1050.
For an overview of multicast routing support over a GRE tunnel, refer to “Support for IPv4 multicast
routing over GRE tunnels” on page 1046. To view information about multicast protocols and GRE
tunnel-specific information, refer to “Displaying multicast protocols and GRE tunneling information”
on page 1062.
NOTE
For the FESX624 module, and 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.