Module_2_-_VLANsStudent - VLANs DTP VTP Etherchannel Edited...

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential BCMSN 2 - 5
1
BCMSN v3.0—2-1
VLANs
DTP
VTP
Etherchannel
Edited by Fiona Mitchell Sept 2014

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential BCMSN 2 - 5
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Virtual Local Area Network (VLAN)

A VLAN is a logical group of end devices.

Broadcasts are contained within VLANs.

Modern design has 1 VLAN = 1 IP subnet.

Trunks connect switches so as to transport multiple VLANs.

Layer 3 devices interconnect VLANs.

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential BCMSN 2 - 5
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End-to-End VLANs

Each VLAN is distributed geographically throughout the network.

Users are grouped into each VLAN regardless of the physical location,
theoretically easing network management.

As a user moves throughout a campus, the VLAN membership for that
user remains the same.
 Switches are configured for VTP server or client mode.

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential BCMSN 2 - 5
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Local VLANs

Create local VLANs with physical boundaries in mind rather than job functions of
the users.

Local VLANs exist between the access and distribution layers.

Traffic from a local VLAN is routed at the distribution and core levels.

Switches are configured in VTP transparent mode.
 Spanning tree is used only to prevent inadvertent loops in the wiring closet.
 One to three VLANs per access layer switch recommended.

Cisco Confidential BCMSN 2 - 5
5
VLANs in Enterprise Campus Design


Benefits of Local VLANs
1. Deterministic traffic flow
2. Active redundant paths
3. High availability
4. Finite failure domain
5. Scalable design

Best Practices for VLAN Design

One to three VLANs per access module and limit those VLANs to a couple of
access switches and the distribution switches.

Avoid using VLAN 1 as the "blackhole" for all unused ports. Use a dedicated
VLAN separate from VLAN 1 to assign all the unused ports.

Separate the voice VLANs, data VLANs, the management VLAN, the native
VLAN, blackhole VLANs, and the default VLAN (VLAN 1).

Avoid VTP when using local VLANs; use manually allowed VLANs on trunks.

For trunk ports, turn off Dynamic Trunking Protocol (DTP) and configure
trunking. Use IEEE 802.1Q rather than ISL because it has better support for
QoS and is a standard protocol.

Manually configure access ports that are not specifically intended for a trunk
link.

Prevent all data traffic from VLAN 1; only permit control protocols to run on
VLAN 1 (DTP, VTP, STP BPDUs, PAgP, LACP, CDP, etc.).

Avoid using Telnet because of security risks; enable SSH support on
management VLANs.

Configuration: Create a VLAN

To create a new VLAN in global configuration mode.
Switch(config)# vlan vlan-id

vlan-id numbers range
Standard VLANs
2-1001
Extended VLANs
025-4094