Differences between ISL and 802.1Q
Conclusion ISL and 802.1Q are two trunking protocols. This tutorial compared both and listed their key differences. Understanding the differences enhances your knowledge about trunking mechanism switches used to exchange VLAN information across the network.
For information on the configuration of ISL / 802 . 1Q encapsulation on Cisco switches, refer to VLAN Trunking Protocols Configuration Examples and TechNotes. ISL Frame The ISL frame consists of three primary fields: the encapsulation frame (original frame), which is encapsulated by the ISL header, and the FCS at the end.
Key Details About Vlan Trunking Isl And 802 1Q
7-4 VLAN Trunking : ISL and 802.1Q As you learned, VLAN trunking allows switches to send Ethernet frames for multiple VLANs across a single link. A trunk interface needs a way to distinguish between Ethernet frames that belong to different VLANs .
Note - Inter-Switch Link ( ISL ) and 802.1Q are used to provide inter-switch VLAN communication. The ISL or 802.1Q frame tagging is removed if a frame is forwarded out to an access-link.
IEEE 802.1Q
IEEE 802.1Q is the networking standard that defines VLAN (Virtual Local Area Network) tagging on Ethernet frames. VLANs allow network administrators to segment a physical network into multiple logical networks, improving security, efficiency, and management.
Trunk links allow multiple VLANs to traverse a single connection between switches 802.1Q is a standard and preferred over Cisco's proprietary ISL protocol for multi-vendor environments
Frame Tagging
Frame Tagging : ISL vs IEEE 802.1Q At layer 2, broadcast domain is divided using VLANs . Every switch port is automatically assigned to VLAN 1. If you configure VLANs other than VLAN 1, you will need to create a switch port trunk that is connected to another switch in order to transport traffic from those VLANs .
Configure an 802.1Q trunk between Cisco switches: tag VLANs , set the native VLAN , prune the allowed list, and verify with show interfaces trunk.
802.1Q VLAN Tagging
Complete CCNA 802.1Q VLAN Tagging guide: tag structure, native VLAN , trunk ports, Q-in-Q, VLAN hopping mitigation, MTU, Cisco IOS configuration, and troubleshooting.
IEEE 802.1Q , often referred to as Dot1q, is the networking standard that supports virtual local area networking ( VLANs ) on an IEEE 802.3 Ethernet network. The standard defines a system of VLAN tagging for Ethernet frames and the accompanying procedures to be used by bridges and switches in handling such frames.