Chapter 15 Configuring Private Vlan - Cisco WS-C3750-48PS-S Software Configuration Manual

Understanding Private VLANs
Figure 15-1 Private-VLAN Domain
Subdomain Subdomain
community VLAN community VLAN
There are two types of secondary VLANs:
Isolated VLANs—Ports within an isolated VLAN cannot communicate with each other at the
•
Layer 2 level.
Community VLANs—Ports within a community VLAN can communicate with each other but
•
cannot communicate with ports in other communities at the Layer 2 level.
Private VLANs provide Layer 2 isolation between ports within the same private VLAN. Private-VLAN
ports are access ports that are one of these types:
Promiscuous—A promiscuous port belongs to the primary VLAN and can communicate with all
•
interfaces, including the community and isolated host ports that belong to the secondary VLANs
associated with the primary VLAN.
• Isolated—An isolated port is a host port that belongs to an isolated secondary VLAN. It has
complete Layer 2 separation from other ports within the same private VLAN, except for the
promiscuous ports. Private VLANs block all traffic to isolated ports except traffic from promiscuous
ports. Traffic received from an isolated port is forwarded only to promiscuous ports.
Community—A community port is a host port that belongs to a community secondary VLAN.
•
Community ports communicate with other ports in the same community VLAN and with
promiscuous ports. These interfaces are isolated at Layer 2 from all other interfaces in other
communities and from isolated ports within their private VLAN.
Trunk ports carry traffic from regular VLANs and also from primary, isolated, and community VLANs.
Note
Catalyst 3750 Switch Software Configuration Guide
15-2
SVI
VLAN
domain
Secondary Secondary
Primary
VLAN
Subdomain Subdomain
Secondary Secondary
isolated VLAN isolated VLAN
Chapter 15 Configuring Private VLANs
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