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What is the difference between tagged and untagged VLANs?
This is also known as the ‘native VLAN’. The switch assigns any untagged frame that arrives on a tagged port to the native VLAN. If a frame on the native VLAN leaves a trunk (tagged) port, the switch strips the VLAN tag out. In short, the native VLAN is a way of carrying untagged traffic across one or more switches. Consider this Example.
When do you need to tag a VLAN port?
Tagging ports will not cause an issue, only devices with the correct VLAN Tag will be able to work properly. You will need to have untagged ports when there is a device that does not support VLAN tagging and is needed on that VLAN network. Thanks for your feedback!
What does Cisco mean by native VLAN tagging?
The native VLAN is a concept retaken from 802.1Q standard that states that each port has a Primary VLAN ID (the native VLAN in Cisco parlance), and may have additional VLAN IDs (tagged VLANs). In order to be compatible with 802.1Q, each device has to implement this concept, resulting into Cisco’s native VLANs on trunks.
What’s the difference between tagged and untagged ports?
Best way to understand this is an Untagged port is an access port and a Tagged port is a trunk port. Always Untag ports that have non VLAN aware devices – like computers and printers. Tag ports to VLAN aware devices – like phones, access points, other switches (this is how you VLAN trunk between switches), etc.
How is an untagged port connected to a host?
An untagged port, or access port on a Cisco switch, connects to hosts (such as a server). The host is unaware of any VLAN configuration. The connected host sends its traffic without any VLAN tag on the frames. When the frame reaches the switch port, the switch will add the VLAN tag.
How did Ethernet networks work before VLANs and switches?
In the old days before switches and VLANs existed, Ethernet networks connected via hubs. Hubs placed all networked hosts onto a single ethernet segment. This was a bit like chaining each host to the next one. This was still an improvement on older token-bus networks. At least a host failure does not cause a break in the chain.
Where does the tag go on an Ethernet frame?
Below is a normal ethernet frame. It consists of: The frame has a four-byte VLAN tag added, which includes the VLAN ID. As shown below, the tag is right after the source MAC. The FCS is also removed during this stage. Finally, the FCS is recalcualted based on the entire frame.