Virtual LANs
A virtual LAN (VLAN) is a logical way to segment a network without changing physical connections. In a VLAN,
broadcast packets or packets with unknown destination addresses are forwarded only to ports that are VLAN
members.
Eliminate need for more routers
Using VLANs, you can increase network segmentation without adding more hardware. VLANs can eliminate the
need for existing routers or for more routers as your network grows. Existing routers can be redeployed to
concentrate on WAN traffic. Think of VLANs as simply a group of end-stations that
can be on multiple physical segments,
●
are not constrained by their physical location,●
can communicate as if they were on a common LAN.●
Major VLAN benefits
Reduces the size of the collision domain and load on servers and workstations by filtering out irrelevant
traffic
●
Eliminates complicated, time-consuming move and change procedures as users change workgroups●
Reduces traffic over routers●
Increases security●
Simple management for more than 4,000 VLANs
Your Switch can support up to 4,096 VLANs and has features that reduce complex VLAN configuration and
management.
Layer 2 VLANs
You can create Layer 2 VLANs based on ports on the Switch or end-station MAC addresses. Port-based VLANs
create immediate and separate collision domains on a single switch or directly-connected switches. MAC
address-based VLANs could be used in environments where laptop users want to connect to the network on any
available network jack.
Layer 3 VLANs
You can create Layer 3 VLANs manually or let the Switch create them automatically. The Switch can currently be
set to automatically create network protocol-based VLANs.
802.1Q VLAN tagging
The Switch supports 802.1Q VLAN tagging, a process whereby the Switch dynamically inserts VLAN
membership information into packets to distribute VLAN membership information across multiple switches.
This VLAN membership information comes from
the administrator configuring specific VLANs
●
the Switch learning VLAN identity by snooping the packets traveling through it●
VLAN-tagged packets are forwarded within the Switch only to ports leading to a VLAN member and outside of
the Switch to other 802.1Q compliant switches.
802.1Q VLAN tagging—externally
The IEEE 802.1Q VLAN tagging standard defined how manufacturers could create devices that would support
VLANs that could span multiple switches from different vendors. This interoperability and traffic containment
across different switches is the result of a switch's ability to use and recognize the 802.1Q Tag Header
.
Switches that implement 802.1Q tagging add this tag header to the frame directly after the destination and
source MAC addresses. Your Switch supports external 802.1Q VLAN tagging, fully described in VLAN Tagging.
802.1Q VLAN tagging—internally
Just as importantly, the adoption of this standard also gave EN a mechanism to streamline traffic within the
Switch itself.
Your Switch, automatically and transparently, makes filtering and forwarding decisions by reading
VLAN membership information contained in the packet header and updating VLAN membership tables by what it
learns. This is how it works: