ITHELPDESK

ISL – Inter-Switch Link – VLAN trunking encapsulation protocol.    Cisco proprietary protocol.   ISL tag each frame with the VLAN ID using 30-byte VLAN header.   ISL tags frames from native VLANs.   ISL encapsulation adds 30 byte high overload header to each Ethernet frame. Hence   it is less preferred compared to 802.1Q encapsulation. Even Cisco stopped supporting   ISL in some of the newer models of LAN switches.  In ISL, VLAN ID size is 15 bits.   IEEE  802.1Q – VLAN trunking encapsulation protocol    IEEE standard protocol. Can be used by all devices from different manufacturers.                 802.1Q tags each frame with the VLAN ID using a 4-byte header.    802.1Q does not add an 802.1Q header to frames in the native VLAN.    802.1Q encapsulation is the most commonly used protocol.     In 802.1Q, 12 b...