Explanation/Reference:
Explanation:
When designing the building access layer, you must consider the number of users or ports required to size up the LAN switch. Connectivity speed for each host should also be considered. Hosts might be connected using various technologies such as Fast Ethernet, Gigabit Ethernet, or port channels. The planned VLANs enter into the design.
Performance in the access layer is also important. Redundancy and QoS features should be considered.
The following are recommended best practices for the building access layer:
Limit VLANs to a single closet when possible to provide the most deterministic and highly available

topology.
Use Rapid Per-VLAN Spanning Tree Plus (RPVST+) if STP is required. It provides the faster

convergence than traditional 802.1d default timers.
Set trunks to ON and ON with no-negotiate.

Manually prune unused VLANs to avoid broadcast propagation (commonly done on the distribution

switch).
Use VLAN Trunking Protocol (VTP) Transparent mode, because there is little need for a common

VLAN database in hierarchical networks.
Disable trunking on host ports, because it is not necessary. Doing so provides more security and

speeds up PortFast.
Consider implementing routing in the access layer to provide fast convergence and Layer 3 load

balancing.
Use the switchport host commands on server and end-user ports to enable PortFast and disable

channeling on these ports.
Use Cisco STP Toolkit, which provides

PortFast: Bypass listening-learning phase for access ports

Loop GuarD. Prevents alternate or root port from becoming designated in absence of bridge protocol

data units (BPDU)
Root GuarD. Prevents external switches from becoming root

BPDU GuarD. Disables PortFast-enabled port if a BPDU is received

Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 3, Page 85