HP Cisco Nexus 5000 Cisco Nexus 5000 Series Switch CLI Software Configuration - Page 138

Broadcast Traffic in Private VLANs, Private VLAN Port Isolation

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Broadcast Traffic in Private VLANs Guidelines and Limitations for Private VLANs Broadcast Traffic in Private VLANs Broadcast traffic from ports in a private VLAN flows in the following ways: • The broadcast traffic flows from a promiscuous port to all ports in the primary VLAN (which includes all the ports in the community and isolated VLANs). This broadcast traffic is distributed to all ports within the primary VLAN, including those ports that are not configured with private VLAN parameters. • The broadcast traffic from an isolated port is distributed only to those promiscuous ports in the primary VLAN that are associated to that isolated port. • The broadcast traffic from community ports is distributed to all ports within the port's community and to all promiscuous ports that are associated to the community port. The broadcast packets are not distributed to any other communities within the primary VLAN, or to any isolated ports. Private VLAN Port Isolation You can use private VLANs to control access to end stations as follows: • Configure selected interfaces connected to end stations as isolated ports to prevent any communication. For example, if the end stations are servers, this configuration prevents communication between the servers. • Configure interfaces connected to default gateways and selected end stations (for example, backup servers) as promiscuous ports to allow all end stations access to a default gateway. Guidelines and Limitations for Private VLANs When configuring private VLANs, follow these guidelines: • You must have already created the VLAN before you can assign the specified VLAN as a private VLAN. • You must enable private VLANs before the switch can apply the private VLAN functionality. • You cannot disable private VLANs if the switch has any operational ports in a private VLAN mode. • Enter the private-vlan synchronize command to map the secondary VLANs to the same Multiple Spanning Tree (MST) instance as the primary VLAN. Related Topics • Mapping Secondary VLANs to Same MSTI as Primary VLANs for Private VLANs, page 188 Configuring a Private VLAN Enabling Private VLANs You must enable private VLANs on the switch to use the private VLAN functionality. Cisco Nexus 5000 Series Switch CLI Software Configuration Guide 92 OL-16597-01

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Broadcast Traffic in Private VLANs
Broadcast traffic from ports in a private VLAN flows in the following ways:
• The broadcast traffic flows from a promiscuous port to all ports in the primary VLAN (which includes
all the ports in the community and isolated VLANs). This broadcast traffic is distributed to all ports
within the primary VLAN, including those ports that are not configured with private VLAN parameters.
• The broadcast traffic from an isolated port is distributed only to those promiscuous ports in the primary
VLAN that are associated to that isolated port.
• The broadcast traffic from community ports is distributed to all ports within the port’s community and
to all promiscuous ports that are associated to the community port. The broadcast packets are not
distributed to any other communities within the primary VLAN, or to any isolated ports.
Private VLAN Port Isolation
You can use private VLANs to control access to end stations as follows:
• Configure selected interfaces connected to end stations as isolated ports to prevent any communication.
For example, if the end stations are servers, this configuration prevents communication between the
servers.
• Configure interfaces connected to default gateways and selected end stations (for example, backup
servers) as promiscuous ports to allow all end stations access to a default gateway.
Guidelines and Limitations for Private VLANs
When configuring private VLANs, follow these guidelines:
• You must have already created the VLAN before you can assign the specified VLAN as a private VLAN.
• You must enable private VLANs before the switch can apply the private VLAN functionality.
• You cannot disable private VLANs if the switch has any operational ports in a private VLAN mode.
• Enter the
private-vlan synchronize
command to map the secondary VLANs to the same Multiple
Spanning Tree (MST) instance as the primary VLAN.
Related Topics
Mapping Secondary VLANs to Same MSTI as Primary VLANs for Private VLANs, page 188
Configuring a Private VLAN
Enabling Private VLANs
You must enable private VLANs on the switch to use the private VLAN functionality.
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
92
OL-16597-01
Guidelines and Limitations for Private VLANs
Broadcast Traffic in Private VLANs