Configure Interswitch VLAN Communication: Cisco Switch and Third-Party Switch

Interswitch VLAN Communication Configuration


An engineer must configure interswitch VLAN communication between a Cisco switch and a third-party switch. Which action should be taken?



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A. B. C. D.


VLAN trunking offers two options, ISL and 802.1Q. ISL is Cisco proprietary while 802.1Q is standards based and supported by multiple vendors.

When configuring VLAN communication between a Cisco switch and a third-party switch, the two switches must be able to understand each other's VLAN tagging methods. VLAN tagging is the process of adding an identifier to Ethernet frames that indicates which VLAN the frame belongs to. The two most common VLAN tagging standards are IEEE 802.1q and ISL (Inter-Switch Link).

Option A - DSCP (Differentiated Services Code Point) - is a mechanism for classifying and prioritizing network traffic, but it is not related to VLAN communication.

Option B - IEEE 802.1q is a VLAN tagging standard used by most vendors, including Cisco. This standard adds a 4-byte tag to Ethernet frames that indicates the VLAN ID.

Option C - ISL is a proprietary VLAN tagging protocol developed by Cisco. While it can be used to communicate between Cisco switches, it may not be compatible with third-party switches.

Option D - IEEE 802.1p is a priority tagging standard used in conjunction with 802.1q VLAN tagging. It allows for the prioritization of traffic within a VLAN, but it is not related to VLAN communication between switches.

Therefore, the correct answer for this question is B. Configure IEEE 802.1q, which is the most widely used VLAN tagging standard and will ensure compatibility between the Cisco switch and the third-party switch.