Portcfgmcastloopback - HP StorageWorks 8B - FC Entry Switch Reference Manual

1
Telnet Commands

portcfgMcastLoopback

Configure a port to receive multicast frames.
Synopsis
portCfgMcastLoopback port, 0|1
Availability
admin
Description
Use this command to configure a port to receive multicast frames. This command allows a user to
dedicate an unused port in a leaf (edge) switch, with no F_Port belonging to a multicast group, to
receive multicast frames.
When multicast frames are received at an edge switch with no member port, traffic will throttle
down in the KBytes/Second range as embedded processor intervention is required to process it.
However when a port is assigned as the multicast loopback port, frames destined for any multicast
group will be routed to that multicast loopback port where it is loopbacked to the port's receiver
which is turned off. This effectively sends the frames to a black hole. Since embedded processor is
not involved, traffic moves at normal (and full) speed.
Executing this command on a branch (middle) switch will not affect traffic. It can be configured for
future use as an edge switch. The disadvantage is that the port cannot be used to connect to other
devices.
The configuration is saved in the non-volatile memory and is persistent across switch reboot or
power cycle.
The user will be prompted if:
•
The selected port is already in use as an E_Port, or Fx_Port,
•
The switch is a branch (middle) switch.
A warning message is printed if another port is already configured as the multicast loopback.
When a port is configured as multicast loopback port:
•
Its port LED will blink a slow green indicating a loopback state. Its laser, if optical GBIC'ed,
will be disabled. It will not respond to any attempt to connect it to any device.
•
The comment field of switchShow will show that it is looped back to itself like so:
•
The portFlags line of portShow will display the "F_PORT" and "INT_LB" flags like so:
•
mcastShow will show the port as a member in its "Member Ports" column.
Operands
This command has the following operands:
port
0|1
1-172
"port 3: sw No_Light
"portFlags: 0x20249
Specify the port number to be configured. Valid values for port number vary
depending on the switch type. This operand is required.
Specify the value 1 and the "portnumber" is dedicated as a multicast loopback
port. Specify the value 0 and the "portnumber" is de-configured from its previous
role as a multicast loopback port. This operand is required.
Loopback->3"
PRESENT F_PORT U_PORT INT_LB LED"
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