Specifications

CHAPTER 2
VLAN Implementation
When planning a VLAN structure, consider traffic flows and link sizing. Take into account the entire traffic pattern of
applications found in your network. For instance, IP voice media traffic travels directly between phones, but signaling
traffic must pass to the Unified Communications Manager. Multicast traffic must communicate back to the routing
process and possibly call upon a Rendezvous Point. Various user applications, such as email and Citrix, place different
demands on the network.
Application flow influences link bandwidth. Remember that uplink ports need to handle all hosts communicating concur-
rently, and although VLANs logically separate traffic, traffic in different VLANs still travels over the same trunk line.
Benchmark throughput for critical application and user data during peak hours; then analyze the results for any bottle-
necks throughout the layered design.
User access ports are typically Fast Ethernet or faster. Access switches must have the necessary port density and can be
either Layer 2 or Layer 3. Ports from user Access to the Distribution layer should be Gigabit Ethernet or better, with an
oversubscription ratio of no more than 20:1. Distribution switches should be multilayer or Layer 3. Links from Distribution
to the Core should be Gigabit Etherchannel or 10-Gig Ethernet, with an oversubscription of no more than 4:1.
VLAN Planning
Before beginning a VLAN implementation, you need to determine the following information:
n VLAN numbering, naming and IP addressing scheme
n VLAN placement—local or multiple switches
n Are any trunks necessary and where?
n VTP parameters
n Test and verification plan
[ 14 ]
© 2010 Pearson Education, Inc. All rights reserved. This publication is protected by copyright. Please see page 112 for more details.
CCNP SWITCH 642-813 Quick Reference by Denise Donohue