Choice the valid encapsulation methods when forcing a device to become a trunk port?
The correct answer is:
Inter-Switch Link (ISL)
ISL is Cisco’s proprietary protocol used to create VLANs in a network. ISL is functioning at the Data-Link layer of the OSI model (layer 2). The size of the encapsulated ISL frames is starting from 94 bytes and can increase up to 1548 due to the additional fields the protocol creates during the encapsulation. The VLAN ID is a 15-bit value found in a 26-byte header of the frame. ISL also adds a 4-byte CRC in the frame for error correction and control.
Today’s standard in trunking is 802.1Q. To better understand how other switches in the network are able to identify a frame belonging to a VLAN, you must know what does the first switch with that frame.
Cisco recommend to use 802.1q as encapsulation method..
Practice Cisco ICND2 v3.0(200-105) exam or IT skills
Practice Cisco ICND2 v3.0(200-105)