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Figure 3-1: Simple VLAN Topology
In this example, each port is manually configured so that the end station attached to the port is a member of
the VLAN configured for the port. The VLAN membership for this network is port-based or static.
3.1.1.
VLAN Tagging
QNOS supports IEEE 802.1Q tagging. Ethernet frames on a tagged VLAN have a 4-byte VLAN tag in the header.
VLAN tagging is required when a VLAN spans multiple switches, which is why trunk ports transmit and
receive only tagged frames.
Tagging may be required when a single port supports multiple devices that are members of different VLANs.
For example, a single port might be connected to an IP phone, a PC, and a printer (the PC and printer are
connected via ports on the IP phone). IP phones are typically configured to use a tagged VLAN for voice
traffic, while the PC and printers typically use the untagged VLAN.
When a port is added to a VLAN as an untagged member, untagged packets entering the switch are tagged
with the PVID (also called the
native VLAN
) of the port. If the port is added to a VLAN as an untagged
member, the port does not add a tag to a packet in that VLAN when it exits the port. Configuring the PVID for
an interface is useful when untagged and tagged packets will be sent and received on that port and a device
connected to the interface does not support VLAN tagging.
When ingress filtering is on, the frame is dropped if the port is not a member of the VLAN identified by the
VLAN ID in the tag. If ingress filtering is off, all tagged frames are forwarded. The port decides whether to
forward or drop the frame when the port receives the frame.
3.1.2.
Double-VLAN Tagging
For trunk ports, which are ports that connect one switch to another switch, QNOS software supports
double- VLAN tagging. This feature allows service providers to create Virtual Metropolitan Area Networks
(VMANs). With double-VLAN tagging, service providers can pass VLAN traffic from one customer domain to
another through a metro core in a simple and cost-effective manner. By using an additional tag on the traffic,
Summary of Contents for QuantaMesh QNOS5
Page 1: ...QuantaMesh Ethernet Switch Configuration Guide QNOS5 NOS Platform ...
Page 209: ...209 Table 7 8 IPv6 Neighbor Discovery Settings ...
Page 226: ...226 Table 8 2 L3 Multicast Defaults ...
Page 254: ...254 Appendix A Term and Acronyms Table 9 5 Terms and Acronyms ...