Types of VLAN :
Default VLAN
Native VLAN
Management VLAN
Voice VLANs
Default VLAN
Native VLAN
Management VLAN
Voice VLANs
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Default VLAN
All
switch ports become a member of the default VLAN after the initial boot
up of the switch. Having all the switch ports participate in the
default VLAN makes them all part of the same broadcast domain. This
allows any device connected to any switch port to communicate with other
devices on other switch ports. The default VLAN for Cisco switches is
VLAN 1. VLAN 1 has all the features of any VLAN, except that you cannot
rename it and you can not delete it. Layer 2 control traffic, such as
CDP and spanning tree protocol traffic, will always be associated with
VLAN 1 - this cannot be changed. In the figure, VLAN 1 traffic is
forwarded over the VLAN trunks connecting the S1, S2, and S3 switches.
It is a security best practice to change the default VLAN to a VLAN
other than VLAN 1; this entails configuring all the ports on the switch
to be associated with a default VLAN other than VLAN 1. VLAN trunks
support the transmission of traffic from more than one VLAN. Although
VLAN trunks are mentioned throughout this section, they are explained in
the next section on VLAN trunking.
Note:
Some network administrators use the term "default VLAN" to mean a VLAN
other than VLAN 1 defined by the network administrator as the VLAN that
all ports are assigned to when they are not in use. In this case, the
only role that VLAN 1 plays is that of handling Layer 2 control traffic
for the network.
Management VLAN
A management VLAN is any VLAN you configure to access the management capabilities of a switch. VLAN 1 would serve as the management VLAN if you did not proactively define a unique VLAN to serve as the management VLAN. You assign the management VLAN an IP address and subnet mask. A switch can be managed via HTTP, Telnet, SSH, or SNMP. Since the out-of-the-box configuration of a Cisco switch has VLAN 1 as the default VLAN, you see that VLAN 1 would be a bad choice as the management VLAN; you wouldn't want an arbitrary user connecting to a switch to default to the management VLAN. Recall that you configured the management VLAN as VLAN 99 in the Basic Switch Concepts and Configuration chapter.
Native VLAN
A
native VLAN is assigned to an 802.1Q trunk port. An 802.1Q trunk port
supports traffic coming from many VLANs (tagged traffic) as well as
traffic that does not come from a VLAN (untagged traffic). The 802.1Q
trunk port places untagged traffic on the native VLAN. In the figure,
the native VLAN is VLAN 99. Untagged traffic is generated by a computer
attached to a switch port that is configured with the native VLAN.
Native VLANs are set out in the IEEE 802.1Q specification to maintain
backward compatibility with untagged traffic common to legacy LAN
scenarios. For our purposes, a native VLAN serves as a common identifier
on opposing ends of a trunk link. It is a best practice to use a VLAN
other than VLAN 1 as the native VLAN.
Management VLAN
A management VLAN is any VLAN you configure to access the management capabilities of a switch. VLAN 1 would serve as the management VLAN if you did not proactively define a unique VLAN to serve as the management VLAN. You assign the management VLAN an IP address and subnet mask. A switch can be managed via HTTP, Telnet, SSH, or SNMP. Since the out-of-the-box configuration of a Cisco switch has VLAN 1 as the default VLAN, you see that VLAN 1 would be a bad choice as the management VLAN; you wouldn't want an arbitrary user connecting to a switch to default to the management VLAN. Recall that you configured the management VLAN as VLAN 99 in the Basic Switch Concepts and Configuration chapter.
Voice VLANs
It is easy to appreciate why a separate VLAN is needed to support Voice over IP (VoIP). Imagine you are receiving an emergency call and suddenly the quality of the transmission degrades so much you cannot understand what the caller is saying. VoIP traffic requires: Assured bandwidth to ensure voice quality
Transmission priority over other types of network traffic Ability to be routed around congested areas on the network
Delay of less than 150 milliseconds (ms) across the network
To meet these requirements, the entire network has to be designed to support VoIP. The details of how to configure a network to support VoIP are beyond the scope of the course, but it is useful to summarize how a voice VLAN works between a switch, a Cisco IP phone, and a computer.
It is easy to appreciate why a separate VLAN is needed to support Voice over IP (VoIP). Imagine you are receiving an emergency call and suddenly the quality of the transmission degrades so much you cannot understand what the caller is saying. VoIP traffic requires: Assured bandwidth to ensure voice quality
Transmission priority over other types of network traffic Ability to be routed around congested areas on the network
Delay of less than 150 milliseconds (ms) across the network
To meet these requirements, the entire network has to be designed to support VoIP. The details of how to configure a network to support VoIP are beyond the scope of the course, but it is useful to summarize how a voice VLAN works between a switch, a Cisco IP phone, and a computer.
In the figure, VLAN 150 is designed to carry voice traffic. The student
computer PC5 is attached to the Cisco IP phone, and the phone is
attached to switch S3. PC5 is in VLAN 20, which is used for student
data. The F0/18 port on S3 is configured to be in voice mode so that it
will tell the phone to tag voice frames with VLAN 150. Data frames
coming through the Cisco IP phone from PC5 are left untagged. Data
destined for PC5 coming from port F0/18 is tagged with VLAN 20 on the
way to the phone, which strips the VLAN tag before the data is forwarded
to PC5. Tagging refers to the addition of bytes to a field in the data
frame which is used by the switch to identify which VLAN the data frame
should be sent to
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