CTS MCT-RACK-12-MGM, Руководство пользователя

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T/L Type/Length Field 2 bytes
Ethernet II “type” or 802.3 “length”
Payload < or = 1500 bytes User data
FCS Frame Check Sequence
4 bytes Cyclical Redundancy Check
Important VLAN Concepts for 802.1Q VLAN Configuration:
There are two key concepts to understand.
-
Access-VLAN specifies the VLAN ID to the port that will assign the VLAN ID to
untagged traffic from that port. A port can only be assigned to one Access-VLAN at a
time. When the port is configured as Access Mode , the port is called an Access Port ,
the link to/from this port is called an Access Link . The VLAN ID assigned is called PVID .
- Trunk-VLAN specifies the set of VLAN IDs that a given port is allowed to receive and
send tagged packets. A port can be assigned to multiple Trunk-VLANs at a time. When
the port is configured as Trunk Mode , the port is called a Trunk Port , the link to/from
this port is called a Trunk Link . The VLAN ID assigned is called VID .
A port can be configured as below 802.1q VLAN modes :
- Access Mode :
Access Links (the link to/from access ports) are the most common type of links on any
VLAN. All
network hosts (such as PCs) connect to the Access Links in order to gain
access to the local network. We configure only one Access-VLAN per port, that is, the
VLAN ID the network hosts will be allowed to access.
It is important to note at this point that any network host connected to an Access Port
is totally unaware of the VLAN assigned to the port. The network host simply assumes
it is part of a single broadcast domain, just as it happens with any normal device. During
data transfers, any VLAN information or data from other VLANs is removed so the
recipient has no information about them.
- Trunk Mode :
Trunk Links (the link to/from trunk ports) is configured to carry packets for multiple
VLANs. These types of ports are usually found in connections between devices. These
links require the ability to carry packets from multiple VLANs because VLANs span over
multiple devices.
- Trunk Native Mode :
A Trunk-native port can carry untagged packets simultaneously with the 802.1Q tagged
packets. When you assign a default Access-VLAN to the trunk-native port, all untagged
traffic travels on the default Access-VLAN for the trunk-native port, and all untagged
traffic is assumed to belong to this Access-VLAN. This Access-VLAN is referred to as
the native VLAN ID for a Trunk-native Port. The native VLAN ID is the VLAN ID that
carries untagged traffic on trunk-native ports.
Example : PortX configuration
Configuration Result
Trunk-VLAN = 10, 11, 12 PortX is an Access Port