ZyXEL MES3500-24F User Guide - Page 90

Chapter 8 Basic Setting VLAN also increases network performance by limiting broadcasts to a smaller and more manageable logical broadcast domain. In traditional switched environments, all broadcast packets go to each and every individual port. With VLAN, all broadcasts are confined to a specific broadcast domain. Note: VLAN is unidirectional; it only governs outgoing traffic. See Chapter 9 on page 97 for information on port-based and 802.1Q tagged VLANs. 8.4.1 Smart Isolation To block traffic between two specific ports within the Switch, you can use port isolation or private VLAN (see Chapter 33 on page 262 for more information). However, it does not work across multiple switches. For example, broadcast traffic from isolated ports on a switch (say B) can be forwarded to all ports on other switches (A and C), including the isolated ports. A B Isolated ports: 2~6 Root port: 7 Designated port: 8 C Smart isolation allows you to prevent isolated ports on different switches from transmitting traffic to each other. After you enable RSTP/MRSTP and smart isolation on the Switch, the designated port(s) will be added to the isolated port list. In the following example, switch A is the root bridge. Switch B's root port 7 connects to switch A and switch B's designated port 8 connects to switch C. Traffic from isolated ports on switch B can only be sent through non-isolated port 1 or root port 7 to switch A. This prevents isolated ports on switch B sending traffic through designated port 8 to switch C. Traffic received on designated port 8 from switch C will not be forwarded to any other isolated ports on switch B. A B Before Smart Isolation: Isolated ports: 2~6 Root port: 7 Designated port: 8 After Smart Isolation: Isolated ports: 2~6, 8 Root port: 7 Designated port: 8 90 C MES3500-24/24F User's Guide