Configuration Guide User guide

1046 FastIron Configuration Guide
53-1002494-02
IPv4 point-to-point GRE tunnels
• When the new PMTUD value is smaller than all of the eight MTU values configured in the
system, the PMTUD feature is disabled for the tunnel, and the value is not added to the
system. For example, the new PMTUD value is 620 which is smaller in value than all of the
eight, different MTU path values configured in the system. The following warning message
is displayed on the CLI:
Warning - All MTU profiles used, disabling PMTU for tunnel <tunnel_id>; new
PMTU was <new pmtu discovered>
Tunnel loopback ports for GRE tunnels
For SX-FI624C, SX-FI624P, SX-FI624HF, and SX-FI62XG modules a physical tunnel loopback port is
required for routing a decapsulated packet. When a GRE-encapsulated packet is received on a
tunnel interface, and the packet needs to be decapsulated, the packet is decapsulated and sent to
the tunnel loopback port. The packet is then looped back and forwarded based on the payload
packets.
If a tunnel loopback port is not configured, tunnel termination is performed by the CPU. Each GRE
tunnel interface can have one assigned tunnel loopback port and the same tunnel loopback port
can be used for multiple tunnels.
Tunnel loopback ports for GRE tunnels are supported on:
• untagged ports
• ports that are enabled by default
• 10 Gbps and 1 Gbps copper and fiber ports
Note the following hardware limitations for these port types:
- On 10 Gbps ports, the port LEDs will be ON (green) when the ports are configured as
tunnel loopback ports for GRE tunnels. Also, the LEDs will blink when data packets are
forwarded.
- On 1 Gbps fiber and copper ports, port LEDs will not be ON when the ports are configured
as tunnel loopback ports for GRE tunnels, nor will the LEDs blink when data packets are
forwarded.
Tunnel loopback ports for GRE tunnels are not applicable on:
• tagged ports
• trunk ports
• ports that are members of a VE
• ports that are disabled
• ports that have an IP address
• flow control
• the SX-FI48GPP module
Support for IPv4 multicast routing over GRE tunnels
PIM-DM and PIM-SM Layer 3 multicast protocols and multicast data traffic are supported over GRE
tunnels. When a multicast protocol is enabled on both ends of a GRE tunnel, multicast packets can
be sent from one tunnel endpoint to another. To accomplish this, the packets are encapsulated
using the GRE unicast tunneling mechanism and forwarded like any other IPv4 unicast packet to