Cisco Sg2008 Manual

							VLAN Management
Setting the Default VLAN
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•PVID—When this option in selected, the port uses the selected VLAN ID as 
its port VLAN ID (PVID). The port assigns the PVID to all untagged frames 
received on the port before forwarding. The following configuration rules 
apply:
-If the interface VLAN mode is General, any VLAN of which the interface is 
a Tagged or Untagged member can be selected to provide the PVID. 
-If the interface VLAN mode is Trunk, the PVID is set to the VLAN ID of 
which the port is a tagged member.
-If the interface VLAN type is Access, the PVID is set to the Access VLAN 
ID and this field cannot be modified.
When you select the Untagged, Tagged, and PVID options and move the VLAN to 
the Selected list, a U, T, and/or P is appended to the VID.
STEP  4Click Apply and then click Close. Your changes are saved to the Running 
Configuration.
Setting the Default VLAN
By default, the switch automatically creates VLAN 1 as the default VLAN for all 
ports and link aggregation groups (LAGs). If a port has no VLAN memberships, the 
switch automatically configures it as a member of the default VLAN. 
You can use the Default VL AN Settings page to change the default VLAN.
When the VID of the default VLAN is changed:
•Ports that were members of the original default VLAN are removed as 
members of that VLAN and are configured as members of the new default 
VLAN.
•The Port VLAN Identifier (PVID) of the ports that were members of the 
original default VLAN is changed to the VID of the new default VLAN.
•If the management VLAN was the same as the original default VLAN, then 
the management VLAN is updated to the new default VLAN provided there 
is at least one member port. If DHCP is enabled, the switch attempts to 
renew the switch IP address through DHCP. 
						

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•The type of the original default VLAN is changed from Default to Static, and 
it can be deleted. One exception is VLAN 1. Even if it is no longer designated 
as the default VLAN, VLAN 1 cannot be deleted.
To  s e l e c t  a  d e f a u l t  V L A N :
STEP 1Click VLAN Management > Default VLAN Settings in the navigation window.
STEP  2Select the VLAN from the list.
STEP  3Click Apply.
Voice and Media
Voice-over-Internet-Protocol (VoIP) allows using a computer data network for 
voice telephone calls. With the increased deployment of delay-sensitive 
applications such as VoIP in modern networks, proper QoS configuration is 
needed to ensure high-quality performance. The Voice and Media feature 
provides a simple classification mechanism for voice packets so that they can be 
prioritized above data packets.
The Voice and Media feature identifies VoIP streams in Ethernet switches and 
provides them with a better Class-of-Service (CoS) than ordinary traffic. The 
switch supports two types of Voice and Media:
•Protocol-based—Identifies a VoIP session using the Session Initiation 
Protocol (SIP) and H.323 control traffic, and assigns these packets the 
highest priority on the voice VLAN.
•OUI-based—Ports that are enabled for this feature automatically become 
members of the configured voice VLAN. The switch detects 
Organizationally Unique Identifier (OUI) values in the first three bytes of the 
MAC addresses in client packets to classify them on the VoIP VLAN and 
prioritize them on the Auto VoIP-enabled ports.
These topics for more information on the configuration pages available in VLAN 
Management > Voice and Media:
•Displaying and Adding Telephony OUI
•Configuring OUI Based Voice and Media
•Configuring SIP/H323 Based Voice and Media 
						

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•Media VLAN
•Auto VoIP Sessions
Displaying and Adding Telephony OUI
The Te l e p h o n y  O U I page lists the Organizationally Unique Identifiers (OUIs) 
associated with different voice VLANs. 
To display this page, click VLAN Management > Voic e and Me dia > Te l e p h o n y  
OUI in the navigation window.
The Telephony OUI Table is preconfigured with identifiers for commonly used 
telephony devices. The administrator can add or remove OUIs. When Voice and 
Media is enabled, ports use the OUI digits in the source and/or destination MAC 
addresses of incoming packets to automatically assign voice traffic to a voice 
VLAN. See Configuring OUI Based Voice and Media for instructions on 
associating the VLAN with an IEEE 802.1p priority and enabling ports for Voice and 
Media. 
To add a new OUI description:
STEP 1Click Add.
STEP  2Specify the following values:
•Te l e p h o n y  O U I—Enter a 3-octet identifier for the telephony application.
•Description—Enter a description of the service such as the vendor name or 
telephony product.
STEP  3Click Apply and Close.
Configuring OUI Based Voice and Media
You can use the Telephony OUI Based Auto VoIP page to:
•Configure an IEEE 802.1p priority level for Voice and Media traffic identified 
using the OUI digits in MAC addresses.
•Specify the VLAN for OUI-based VoIP packets. Although you can assign a 
VLAN ID that has not yet been created on the switch, you must 
subsequently create the VLAN for the feature to be operational (see 
Creating VLANs). 
						

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•Enable ports for this feature. When enabled on a port, the port is 
automatically made member of the configured voice VLAN when the switch 
receives an OUI frame (the administrator does not need to manually add the 
port as a member of the VLAN).
The Por t VL AN Membership page shows that the port is a member of the Voice 
VLAN.
To configure OUI-based Voice and Media:
STEP 1Click VLAN Management > Voice and Media > Te l e p h o n y  O U I  B a s e d in the 
navigation window.
STEP  2Check VLAN to enable modifying the VLAN ID and Priority fields.
STEP  3In the VLAN ID field, specify the VLAN to carry voice traffic. This VLAN should 
already be configured on the switch (see Creating VLANs).
STEP  4In the Priority field, specify the IEEE 802.1p Class-of-Service (CoS) priority level for 
VoIP traffic.
STEP  5Click Apply. Your changes are saved to the Running Configuration.
STEP  6In the Telephony OUI Based Interface Settings Table, select an interface to 
configure, and then click Edit. 
NOTE: Set the an auto VoIP port to be a General port, not a Trunk or Access port.
STEP  7Select Enable for the Auto VoIP mode. The port is automatically added as a 
member of the voice VLAN.
STEP  8Click Apply and then click Close. Your changes are saved to the Running 
Configuration.
Configuring SIP/H323 Based Voice and Media
You can use the SIP/H323 Based Auto VoIP page to configure the switch to 
recognize VoIP traffic by its protocol, such as the Session Initiation Protocol (SIP) 
and H.323. The traffic is automatically assigned the highest priority available on 
the system.
To configure SIP/H323 based Voice and Media: 
						

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STEP 1Click VLAN Management > Voice and Media > SIP/H323 Based in the navigation 
window.
The table lists the administrative and operational statuses for SIP/H323 Auto VoIP 
on each interface, and shows the class that traffic will be assigned to. The traffic 
class corresponding to the highest priority queue on the port is chosen 
automatically.
STEP  2Use the Interface Type menu to display ports or LAGs in the SIP/H323 Based 
Interface Settings Table.
STEP  3Select the port or LAG interface to configure and click Edit. 
STEP  4Select Enable for the Auto VoIP Mode.
STEP  5Click Apply and then click Close. Your changes are saved to the Running 
Configuration.
Media VLAN
The Media VLAN feature enables switch ports to carry voice, video, and signaling 
traffic with an assigned priority value. Assigning different priorities to traffic 
enables separation of media and data traffic coming into a port. The Media VLAN 
feature helps to ensure that the sound or video quality of an IP phone or video 
device is safeguarded from deterioration when data traffic on the port is high.
The inherent traffic isolation provided by VLANs ensures that inter-VLAN traffic is 
under management control and that network-attached clients cannot initiate a 
direct attack on voice components. The switch uses the IP-DSCP or 802.1p value 
in packets from media devices to assign this traffic to high priority queues.
The switch uses Media VLANs to support LLDP-MED applications. (See LLDP-
MED for information on the protocol.) Each Media VLAN corresponds to an LLDP-
MED application for a specific type of media traffic. The LLDP-MED applications 
are voice, voice signaling, guest voice, guest voice signaling, softphone voice, 
video conferencing, streaming video, and video signaling. Each Media VLAN is 
associated with the following parameters 
•A VLAN with optional VLAN tagging
•An IEEE 802.1p priority value
•A DSCP value 
						

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When a port is LLDP-MED enabled with network policy, the switch will advertise 
its Media VLANs in the LLDP-MED network policy TLVs out to the port. When a 
LLDP Media Endpoint is discovered, the switch will install the Media VLAN at the 
corresponding port. You can enable LLDP-MED and networking policy in the 
Administration > Discovery - LLDP pages.
Media VLAN is enabled and disabled globally. Each application and its Media 
VLAN is configured on a per-port basis. For example, Guest Voice can be on 
Media VLAN 1 on interface g1, but can be on Media VLAN 10 on interface g2. 
The Media VLAN Interface Settings Table displays each media traffic type that 
can be enabled, and shows its status and settings on the selected port.
To configure Media VLAN applications:
STEP 1Click VLAN management > Voice and Media > Media VLAN in the navigation 
window.
STEP  2Select Enable for Admin Mode to globally enable this feature on the switch, and 
then click Apply.
STEP  3Select an interface to configure from the Interface list.
!
CAUTIONPorts that are members of a LAG cannot be enabled for Media VLAN applications 
(see Configuring LAGs).
STEP  4From the Application list, select the media traffic type to configure:
•Vo ic e
•Voice Signaling
•Guest Voice
•Guest Voice Signaling
•Softphone Voice
•Video Conferencing
•Streaming Video
•Video Signaling
STEP  5Click Edit. 
						

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STEP  6For Application Status, select Enable to enable priority assignment for the 
selected application. Uncheck the box to disable this feature. 
STEP  7If you enabled Application Status, enable or disable the following features:
•Untagged—Select Enable if the media device (LLDP-MED Endpoint) will 
send untagged packets. The network policy TLV from the switch must also 
indicate this expectation, and a media device must acknowledge that it will 
use untagged frames. Uncheck the box to disable this feature.
•VLAN and VLAN ID—Select Enable to specify a VLAN, and then choose a 
VLAN ID from the list. Uncheck the box to disable this feature.
•Priority and Priority Value—Select Enable to prioritize packets of the 
selected application. Then enter an IEEE 802.1p class-of-service priority 
tagging value for Media VLAN traffic. The priority tag range is 0–7. 
•DSCP and DSCP Value—Select Enable to specify a DSCP for the selected 
application. Then enter a DSCP value for the port. The range is 0-63. 
STEP  8Click Apply and then click Close. Your changes are saved to the Running 
Configuration.
STEP  9Ensure that LLDP-MED is enabled on the interface. You can click Enable LLDP-MED 
Network Policy to display the LLDP-MED Por t Settings page. See LLDP-MED for 
more information.
Auto VoIP Sessions
The Auto VoIP Sessions page displays information about the source, destination, 
and protocol for each Voice over IP session. 
						

							6
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Spanning Tree
This chapter describes how to configure the Spanning Tree Protocol (STP) on the 
switch. 
It includes the following topics:
•Overview of Spanning Tree
•Configuring STP Status and Global Settings
•Configuring STP Interface Settings
•RSTP Interface Settings
Overview of Spanning Tree
STP enables efficient communication on a network that includes multiple bridges. 
Devices on these networks can learn multiple (that is, redundant) paths to the 
same endpoint. While path redundancy is desirable for maintaining traffic flow 
when particular links are down, it can lead to a traffic loops that affect network 
performance and confuse forwarding algorithms.
Each STP-enabled bridge exchanges Bridge Protocol Data Units (BPDUs) with 
other bridges. BPDUs identify the bridge port MAC addresses and the priority and 
cost associated with each port. STP uses this information to build a topology that 
provides one active path between any two stations on the network. Duplicate 
paths between those stations are placed in a stand-by state for use only when the 
active path becomes unavailable.
BPDU exchanges also facilitate the election of a root bridge and root port for the 
network. The root bridge provides a reference point that each other bridge uses to 
calculate a lowest-cost path by summing the cost of the ports in each path and 
choosing the one with the lowest total. The port that connects a bridge to the 
lowest-cost path is called the bridge’s root por t. 
						

							Spanning Tree
Configuring STP Status and Global Settings
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When the root bridge is selected and each root port is established, each network 
segment can then determine which bridge provides the lowest cost path to the 
root port. The port that provides this path is named the designated por t for the 
network segment. Spanning tree disables other ports for that network segment or 
designates them as alternate or backup ports.
Supported spanning tree versions include Common Spanning Tree (CST) and 
Rapid STP (RSTP). This switch does not support Multiple STP (MSTP).
•CST (IEEE 802.1D) is the original protocol version that provides a single path 
between end stations, avoiding and eliminating loops.
•RSTP (IEEE 802.1D-2004 or IEEE 802.1w) provides protocol enhancements 
that enable a network to more quickly achieve an optimal STP topology. 
Spanning tree is enabled by default and set to be RSTP.
Configuring STP Status and Global Settings
You can use the STP Status & Global Set tings page to enable STP, select the STP 
mode of operation, and configure bridge priority settings. You can also view status 
information about the STP topology. To display this page, click Spanning Tree> 
STP Status & Global Settings in the navigation window.
This page enables you to configure global settings and bridge settings, and 
displays information about the designated root.
Configuring Global and Bridge Settings
To configure STP global settings and bridge settings:
STEP 1Specify the following global settings:
•Spanning Tree State—Select to enable STP operation on the switch. You 
must also enable STP operation on individual ports (see Configuring STP 
Interface Settings). 
						

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Configuring STP Status and Global Settings
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•STP Operation Mode—Select one of the following STP modes: 
-Classic STP—Operates according to the original IEEE 802.1D spanning 
tree protocol.
-Rapid STP—Is the default value and provides faster spanning tree 
convergence after a topology change than does classic STP. 
•BPDU Handling—Bridge Protocol Data Units (BPDUs) are the messages 
exchanged between switches to calculate STP topology. Select the method 
of BPDU packet handling when the spanning tree is disabled on an inter face :
-Filtering—Enables the port to discard BPDUs received on interfaces that 
are not enabled for STP.
-Flooding—Allows flooding of BPDUs received on non-spanning-tree 
ports to all other non-spanning-tree ports.
STEP  2Specify the following bridge setting:
•Priority—The bridge priority value. When switches or bridges are running 
STP, each is assigned a priority. After exchanging BPDUs, the switch with the 
lowest bridge identifier becomes the root bridge. The bridge priority must 
be a multiple of 4096. If you specify a priority that is not a multiple of 4096, 
the priority is automatically set to the next lowest multiple of 4096. For 
example if you attempt to set the priority to any value between 0 and 4095, 
it will be set to 0. The default priority is 32768. The valid range is 0-61440.
•CST Bridge Max Age—The amount of time in seconds that a bridge waits 
before implementing a topological change. The valid range is 6-40 seconds. 
The default is 20 seconds.
•CST Bridge Forward Delay—The amount of time in seconds that a bridge 
remains in a listening and learning state before forwarding packets. The valid 
range is 4-30 seconds. The default is 15 seconds.
The following information appears in this section of the page:
•Hello Time—The interval at which a bridge sends configuration messages. 
•Max Hops—The number of hops before a BDPU is discarded and the port 
information is aged out. The maximum hop count is set to 20 and is not 
configurable.
•Hold Time—The minimum time period, in seconds, that elapses between 
the transmission of Configuration BPDUs through a bridge port.