Although the basic concept of frame tagging is the same with both methods, there are differences in how it is accomplished. If two devices are to perform trunking, they must agree to use either ISL or In the case of ISL, the tag is external to the Ethernet frame, which is the same as encapsulating the Ethernet frame.
IEEE In contrast to ISL, This bit field carries the information used to deterministically identify the VLAN the Ethernet frame belongs to. The range of hexadecimal values is from 0x to 0xFFF for a bit number. Easy Normal Medium Hard Expert. Writing code in comment? Please use ide. Load Comments. What's New. Most popular in Computer Networks. Trunking ports support the transmission of tagged frames as well as untagged frames through the interface.
Some devices are sending by default are tagging the VLAN traffic. If such traffic arrives in a native VLAN interface, the switch will drop the frame. The traffic sent to a native VLAN interface should always be untagged. The only solution for this problem if you need that switch port to be configured as native is to configure the other devices to send the traffic untagged.
The default native VLAN is 1, but when you configure a To enable a port in trunking mode, you can use the switchport mode trunk interface configuration command. You can also check the status of the interface with show interfaces interface switchport.
This address is a multicast address and is set at "0xC" or "0xc". The TYPE field consists of a 4-bit code. The TYPE field indicates the type of frame that is encapsulated and can be used in the future to indicate alternative encapsulations. This table provides definitions of different TYPE codes:. The USER field consists of a 4-bit code. The default USER field value is "". For Ethernet frames, the USER field bits "0" and "1" indicate the priority of the packet as it passes through the switch.
Whenever traffic can be handled in a manner that allows it to be forwarded more quickly, the packets with this bit set should take advantage of the quick path. It is not required that such paths be provided. The field should be set to the " It is a bit value. The receiving device may ignore the SA field of the frame. The LEN field stores the actual packet size of the original packet as a bit value.
The total length of the excluded fields is 18 bytes, so the LEN field represents the total length minus 18 bytes. The HSA field is a bit value. This field represents the upper 3 bytes the manufacturer ID portion of the SA field.
The field must contain the value "0xC". It is a bit value that is used to distinguish frames on different VLANs. This field is often referred to as the "color" of the frame.
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