ZyXEL GS1510-24 User Guide - Page 64

Port Isolation

Page 64 highlights

Chapter 10 VLAN The CFI (Canonical Format Indicator) is a single-bit flag, always set to zero for Ethernet switches. If a frame received at an Ethernet port has a CFI set to 1, then that frame should not be forwarded as it is to an untagged port. The remaining twelve bits define the VLAN ID, giving a possible maximum number of 4,096 VLANs. Note that user priority and VLAN ID are independent of each other. A frame with VID (VLAN Identifier) of null (0) is called a priority frame, meaning that only the priority level is significant and the default VID of the ingress port is given as the VID of the frame. Of the 4096 possible VIDs, a VID of 0 is used to identify priority frames and value 4095 (FFF) is reserved, so the maximum possible VLAN configurations are 4,094. TPID User Priority 2 Bytes 3 Bits CFI VLAN ID 1 Bit 12 bits 10.3.2 Forwarding Tagged and Untagged Frames Each port on the Switch is capable of passing tagged or untagged frames. To forward a frame from an 802.1Q VLAN-aware switch to an 802.1Q VLAN-unaware switch, the Switch first decides where to forward the frame and then strips off the VLAN tag. To forward a frame from an 802.1Q VLAN-unaware switch to an 802.1Q VLAN-aware switch, the Switch first decides where to forward the frame, and then inserts a VLAN tag reflecting the ingress port's default VID. The default PVID is VLAN 1 for all ports, but this can be changed. A broadcast frame (or a multicast frame for a multicast group that is known by the system) is duplicated only on ports that are members of the VID (except the ingress port itself), thus confining the broadcast to a specific domain. 10.4 Port Isolation Use this screen to restrict specific ports on the Switch from communicating with each other. This screen can also be used to specify which ports will forward received packets to other ports on the Switch. 64 GS1510 Series User's Guide

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Chapter 10 VLAN
GS1510 Series User’s Guide
64
The CFI (Canonical Format Indicator) is a single-bit flag, always set to zero for
Ethernet switches. If a frame received at an Ethernet port has a CFI set to 1, then
that frame should not be forwarded as it is to an untagged port. The remaining
twelve bits define the VLAN ID, giving a possible maximum number of 4,096
VLANs. Note that user priority and VLAN ID are independent of each other. A
frame with VID (VLAN Identifier) of null (0) is called a priority frame, meaning that
only the priority level is significant and the default VID of the ingress port is given
as the VID of the frame. Of the 4096 possible VIDs, a VID of 0 is used to identify
priority frames and value 4095 (FFF) is reserved, so the maximum possible VLAN
configurations are 4,094.
10.3.2
Forwarding Tagged and Untagged Frames
Each port on the Switch is capable of passing tagged or untagged frames. To
forward a frame from an 802.1Q VLAN-aware switch to an 802.1Q VLAN-unaware
switch, the Switch first decides where to forward the frame and then strips off the
VLAN tag. To forward a frame from an 802.1Q VLAN-unaware switch to an 802.1Q
VLAN-aware switch, the Switch first decides where to forward the frame, and then
inserts a VLAN tag reflecting the ingress port's default VID. The default PVID is
VLAN 1 for all ports, but this can be changed.
A broadcast frame (or a multicast frame for a multicast group that is known by the
system) is duplicated only on ports that are members of the VID (except the
ingress port itself), thus confining the broadcast to a specific domain.
10.4
Port Isolation
Use this screen to restrict specific ports on the Switch from communicating with
each other.
This screen can also be used to specify which ports will forward
received packets to other ports on the Switch.
TPID
2 Bytes
User Priority
3 Bits
CFI
1 Bit
VLAN ID
12 bits