Questions derived from the 642-812 – Building Converged Cisco Multilayer Switched Networks (BCMSN) Cisco Self Test Software Practice Test.
Objective: Implement VLANs
SubObjective: Explain and configure VLAN trunking (i.e., IEEE 802.1Q and ISL)
Item Number: 642-8126.96.36.199
Single Answer, Multiple Choice
Which are valid configurable VLAN ID numbers for 802.1Q networks?
IEEE 802.1Q supports configuring VLAN IDs 1-4094.
An 802.1Q standard specifies support for a maximum of 4,094 VLANs (IDs 0 and 4095 are reserved). Therefore, ID values of 1-4094 are assignable. In contrast, the valid range of configurable ISL VLANs is 1-1001. The following is a summary of VLAN IDs:
- 0 and 4095: Reserved
- 1 – Cisco default management
- 2-1001: Available for Ethernet VLANs
- 1002-1005: Defaults for FDDI and Token Ring VLANs
- 1006-4094: Extended range available for Ethernet VLANs (802.1Q only)
Recognizing the difference in supported VLAN ID ranges highlights several issues in constructing a network of both ISL and 802.1Q VLAN networks. Ethernet VLAN IDs above the supported ISL range must be mapped to IDs within the range supported by ISL. Among other limitations, you are limited to a total of eight mappings. This process of mapping 802.1Q to ISL VLAN IDs will further restrict and define which IDs are available to be used.