Linksys LGS528 User Manual
User Guide
Managed Switch
LGS5XX
1
Contents
Chapter 1 - Getting Started ............................................................................... 6
Configuring the Console Port .............................................................................................................. 6
Interface Naming Conventions ........................................................................................................... 8
Window Navigation.................................................................................................................................. 9
Chapter 2 - System Status .............................................................................. 11
System Summary ................................................................................................................................. 11
RMON ........................................................................................................................................................ 12
Interface Statistics .............................................................................................................................. 20
Chapter 3 - Quick Start ..................................................................................... 23
Chapter 4 - System Management .................................................................. 24
System Information ............................................................................................................................. 24
TCAM Resources .................................................................................................................................. 25
Management Session Timeout ........................................................................................................ 27
Time ........................................................................................................................................................... 28
SNMP ........................................................................................................................................................ 36
Logs ........................................................................................................................................................... 58
Chapter 5 - Port Management ........................................................................ 63
Ports .......................................................................................................................................................... 63
Chapter 6 - VLAN Management ...................................................................100
Overview ............................................................................................................................................... 100
VLANs .................................................................................................................................................... 102
Interfaces ............................................................................................................................................. 106
VLAN Memberships .......................................................................................................................... 110
GVRP ...................................................................................................................................................... 112
VLAN Groups....................................................................................................................................... 113
2
Voice VLAN .......................................................................................................................................... 118
Chapter 7 - Spanning Tree .............................................................................123
Overview ............................................................................................................................................... 123
Spanning Tree ..................................................................................................................................... 124
STP Interfaces .................................................................................................................................... 126
RSTP Interfaces ................................................................................................................................. 127
MSTP Properties ................................................................................................................................ 130
VLAN to MSTP .................................................................................................................................... 130
MSTP Instance Status ..................................................................................................................... 133
MSTP Instance Interface ................................................................................................................ 134
Chapter 8 - MAC Address Management ...................................................138
Dynamic MAC Addresses ............................................................................................................... 139
Static MAC Addresses .................................................................................................................... 140
Reserved MAC Addresses ............................................................................................................. 141
Chapter 9 - Multicast .......................................................................................143
Overview ............................................................................................................................................... 143
Feature Configuration ..................................................................................................................... 145
IGMP/MLD Snooping ........................................................................................................................ 147
IGMP Snooping ................................................................................................................................... 149
MLD Snooping .................................................................................................................................... 151
Multicast Router Ports .................................................................................................................... 152
Forward All ........................................................................................................................................... 153
Unregistered Multicast ................................................................................................................... 155
IGMP/MLD IP Group Addresses ................................................................................................... 156
MAC Group Address FDB ............................................................................................................... 158
IP Group Address FDB ..................................................................................................................... 161
Chapter 10 - IP Interface ................................................................................163
IPv4 ......................................................................................................................................................... 163
IPv6 ......................................................................................................................................................... 172
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Chapter 11 - IP Network Operations ..........................................................185
Domain Name System ...................................................................................................................... 185
DHCP ...................................................................................................................................................... 187
IP Source Guard ................................................................................................................................. 197
DHCP Snooping Binding Database ............................................................................................. 205
ARP Inspection ................................................................................................................................... 208
Interface Settings ............................................................................................................................. 213
Chapter 12 - Security ......................................................................................214
Management Security ..................................................................................................................... 214
RADIUS ................................................................................................................................................. 222
Network Access Control ................................................................................................................. 227
Port Security ....................................................................................................................................... 239
Storm Control ..................................................................................................................................... 241
Chapter 13 - Access Control List ................................................................243
Access Control Lists ........................................................................................................................ 243
MAC-Based ACL/ACE ...................................................................................................................... 245
IPv4-Based ACL/ACE ...................................................................................................................... 247
IPv6-Based ACL/ACE ...................................................................................................................... 250
ACL Binding ......................................................................................................................................... 252
Chapter 14 - Quality of Service ....................................................................254
Overview ............................................................................................................................................... 254
Feature Configuration ..................................................................................................................... 257
Queue Scheduling ............................................................................................................................. 258
CoS/802.1p to Queue ..................................................................................................................... 260
DSCP to Queue................................................................................................................................... 262
Bandwidth Control ............................................................................................................................ 263
Egress Shaping .................................................................................................................................. 265
Basic QoS ............................................................................................................................................. 266
Advanced QoS .................................................................................................................................... 267
QoS Statistics .................................................................................................................................... 279
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Chapter 15 – Maintenance .............................................................................281
Device Models..................................................................................................................................... 281
System Mode & Reboot ................................................................................................................... 282
File Management ............................................................................................................................... 283
Diagnostics .......................................................................................................................................... 294
Chapter 16 - Support .......................................................................................301
Appendix ...............................................................................................................302
Startup Menu Procedures .............................................................................................................. 302
5
Chapter 1 - Getting Started
This section provides an introduction to the Web-based configuration utility, and covers the
following topics:
•
Configuring with the Console Port
•
Launching the Configuration Utility
•
Interface Naming Conventions
•
Window Navigation
Configuring the Console Port
To configure with the Console Port:
1. Use a provided serial cable to connect to console port
2. Start a terminal application such as Hyper Terminal on your computer
3. Configure the utility with 11520 bit per second, 8 data bits, no parity, 1 stop bit and no
flow control. (The firmware supports autobaud detection, the device will detect the speed
after pressing Enter.)
4. Type in default user name: admin, and password: admin
5. Enter to access menu CLI
The following menu is displayed:
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1. Enter your user name and password.
The main menu is displayed:
2. Continue configuring the device.
3. Click Logout to log out of the CLI menu.
Launching the Configuration Utility
This section describes how to navigate the Web-based switch configuration utility. If you are
using a pop-up blocker, make sure it is disabled.
The following browsers are supported:
•
Firefox (versions 16 and latest)
•
IE version (versions 9, 10)
•
Chrome (version 35 and latest)
Note—If you are using IPv6 interfaces on your management station, use the IPv6 global address
and not the IPv6 link local address to access the device from your browser.
To open the Web-based configuration utility:
1. Open a Web browser.
2. Enter the IP address of the device you are configuring in the address bar on the browser,
and then press Enter.
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Note—When the device is using the factory default IP address of
192.168.1.
251, its power
LED flashes
administrator-configured
To log in:
The default username is admin and the default password is admin.
1. Open the GUI. The Login page is displayed.
2. Enter the username/password. The password can contain up to 64 ASCII characters.
To log out:
By default, the application logs out after ten minutes of inactivity.
CAUTION
Unless the Running Configuration is copied to the Startup Configuration, rebooting the
device will remove all changes made since the last time the file was saved. Save the
Running Configuration to the Startup Configuration before logging off to preserve any
changes you made during this session.
When you click Quick Start > Save Your Configurations, the Configuration File Copy page appears.
Save the Running Configuration file by copying it to the Startup Configuration file.
continuously.
When the device is using a DHCP assigned IP address or an
static IP address, the power LED is on solid.
To log out, click Logout in the top right corner of any page. The system logs out of the device.
When a timeout occurs or you intentionally log out of the system, a message appears and the Login
page appears, with a message indicating the logged-out state.
Interface Naming Conventions
Within the GUI, interfaces are denoted by linking the following elements:
•
Interface Number: Port, LAG or VLAN ID
8
Window Navigation
artup Configuration file type on the device.
This section describes the features of the Web-based switch configuration utility.
Application Header
The Application Header appears on every page. It provides the following application links:
Application Link Name Description
Logout Click to log out of the Web-based switch configuration utility.
Firmware Version Display the device version number.
Help Click for the link to this administration guide.
Management Buttons
The following table describes the commonly used buttons that appear on various pages in the
system.
Button Name Description
Add Click to display the related Add page and add an entry to a table.
Enter the information and click Apply to save it to the Running
Configuration. Click Close to return to the main page. Click Save
to display the Configuration File Copy page and save the Running
Configuration to the St
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Apply Click to apply changes to the Running Configuration on the
device. If the device is rebooted, the Running Configuration is lost
unless it is saved to the Startup Configuration file type or another
are cleared.
Clear All
Click to clear the statistic counters for all interfaces.
all interface, or log files.
entry and click Edit. The Edit page appears, and the
are displayed on the page.
Refresh
Click Refresh to refresh the counter values.
Test or Start
Click Test to perform the related tests.
selected or for all entries (respectively).
file type. Click Save to display the Configuration File Copy page
and save the Running Configuration to the Startup Configuration
file type on the device.
Button Name Description
Close Click to return to the previous page. Any changes not applied
Clear Click to clear information, such a counters of an interface or
Delete After selecting an entry in the table, click Delete to remove.
Edit Select the
entry can be modified.
1. Click Apply to save the changes to the Running
Configuration.
2. Click Close to return to the main page.
Search Enter the query filtering criteria and click Search. The results
View or View All Click View to display details associated with the entry
10
Chapter 2 - System Status
This section describes how to view device statistics. It covers the following topics:
•
•
•
System Summary
System Summary
RMON
Interface Statistics
The System Summary page provides a graphic view of the device, and displays device status,
hardware information, firmware version information, general PoE status, and other items.
To view system information, click System Status > System Summary. The System Summary page
contains system and hardware information.
•
System Mode------Specifies whether the system is operating in Layer 2 or Layer 3 system
mode.
•
System Description------ A description of the system.
•
System Location------Physical location of the device. Click Edit to go the System Information
page to enter this value.
•
System Contact------Name of a contact person. Click Edit to go the System Information
page to enter this value.
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•
Host Name------Name of the device. By default, the device host name is composed of the
name of the switch followed by the final six digits in the device’s MAC address.
•
Base MAC Address------Device MAC address.
•
SNMP Object ID------ The unique vendor identification of the network management
subsystem assigned by Internet Assigned Numbers Authority
•
Firmware Version------ Firmware version number.
•
Boot Code Version------Boot version number.
•
Hardware Version ------Hardware version number of the device.
•
Serial Number------ Serial number.
•
Device Status
•
Fan Status------ Applicable only to models that have fans. The following values are possible:
-
-
•
Date & Time------ System date and time.
•
System Uptime------ Length of time since last reboot.
OK------ Fan is operating normally.
Fail------Fan is not operating correctly.
RMON
Statistics
The Statistics page displays detailed information regarding packet sizes and information
regarding physical layer errors. The information displayed is according to the RMON (Remote
Network Monitoring) standard. An oversized packet is defined as an Ethernet frame with the
following criteria:
•
Packet length is greater than MRU byte size.
•
Collision event has not been detected.
•
Late collision event has not been detected.
•
Received (Rx) error event has not been detected.
• Packet has a valid CRC.
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To view RMON statistics and/or set the refresh rate:
1. Click System Status > RMON > Statistics.
2. Select the Interface for which statistics are to be displayed.
3. Select the Refresh Rate, the time period that passes before the interface statistics are
refreshed.
The statistics are displayed for the selected interface.
•
Bytes Received------ Number of octets received, including bad packets and
FCS octets, but excluding framing bits.
•
Drop Events------Number of packets dropped.
•
Packets Received------ Number of good packets received, including Multicast and
Broadcast packets.
•
Broadcast Packets Received------Number of good Broadcast packets received. This
number does not include Multicast packets.
•
Multicast Packets Received------Number of good Multicast packets received.
•
CRC & Align Errors------ Number of CRC and Align errors that have occurred.
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•
Undersize Packets------Number of undersized packets (less than 64 octets) received.
•
Oversize Packets------Number of oversized packets (over 2000 octets) received.
•
Fragments------Number of fragments (packets with less than 64 octets, excluding
framing bits, but including Frame Check Sequence octets) received.
•
Jabbers------ Total number received packets that were longer than 1632 octets. This
number excludes frame bits, but includes FCS octets that had either a bad FCS
with an integral number of octets (FCS Error) or a bad FCS with a non-integral
octet (Alignment Error) number.
A jabber packet is defined as an Ethernet frame that satisfies the following
criteria:
-
Packet data length is greater than MRU.
-
Packet has an invalid CRC.
-
Received (Rx) Error Event has not been detected.
• Collisions------Number of collisions received. If Jumbo Frames are enabled, the
threshold of Jabber Frames is raised to the maximum size of Jumbo Frames.
• Frames of 64 Bytes------Number of frames, containing 64 bytes that were
received.
• Frames of 65 to 127 Bytes------Number of frames, containing 65-127 bytes that
were received.
• Frames of 128 to 255 Bytes------Number of frames, containing 128-255 bytes
that were received.
• Frames of 256 to 511 Bytes------Number of frames, containing 256-511 bytes
that were received.
• Frames of 512 to 1023 Bytes------Number of frames, containing 512-1023
bytes that were received.
• Packets of 1024 and More Bytes------ Number of frames, containing 1024-2000
bytes, and Jumbo Frames, that were received.
To clear or view statistics counters:
•
Click Refresh to refresh the counters on the page.
•
Click Clear to clear the selected interfaces counters.
•
Click View All to see all ports on a single page.
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RMON History
The RMON feature enables monitoring statistics per interface.
The History Control Table page defines the sampling frequency, amount of samples to store and
the port from which to gather the data.
After the data is sampled and stored, it appears in the History Table page that can be viewed by
clicking the History button.
To enter RMON control information:
1. Click System Status > RMON > History.
2. Click Add.
3. Enter the parameters.
•
New History Control Entry Index ------Displays the number of the new History table
entry.
•
Source Interface------Select the type of interface from which the history samples are
to be taken.
•
Maximum Samples------ Enter the number of samples to store.
•
Samples Collected------RMON is allowed by the standard to not grant all requested
samples, but rather to limit the number of samples per request. Therefore, this
field represents the sample number actually granted to the request that is equal or
less than the requested maximum sample.
•
Sampling Interval------ Enter the time in seconds that samples are collected from the
ports. The field range is 1-3600.
•
Owner------Enter the RMON station or user that requested the RMON information.
4. Click Apply. The entry is added to the History Control Table page, and the Running
Configuration file is updated.
15
5. Click the History button (described below) to view the actual statistics.
RMON History Table
The History Table page displays interface-specific statistical network samplings. The
samples were configured in the History Control table described above.
To view RMON history statistics:
1. Click System Status > RMON > History.
2. Click History.
3. From the History Control Entry Index drop-down menu, select the entry number of the
sample to display.
The fields are displayed for the selected sample.
•
Owner------History table entry owner.
•
Sample Index------ Statistics were taken from this sample.
•
Drop Events------Dropped packets due to lack of network resources during the
sampling interval. This may not represent the exact number of dropped
packets, but rather the number of times dropped packets were detected.
•
Bytes Received------ Octets received including bad packets and FCS octets, but
excluding framing bits.
•
Packets Received------ Packets received, including bad packets, Multicast, and
Broadcast packets.
•
Broadcast Packets------Good Broadcast packets excluding Multicast packets.
•
Multicast Packets------Good Multicast packets received.
•
CRC Align Errors------CRC and Align errors that have occurred.
•
Undersize Packets------Undersized packets (less than 64 octets) received.
•
Oversize Packets------Oversized packets (over 2000 octets) received.
•
Fragments------Fragments (packets with less than 64 octets) received, excluding
framing bits, but including FCS octets.
•
Jabbers------ Total number of received packets that were longer than 2000
octets. This number excludes frame bits, but includes FCS octets that had
either a bad FCS (Frame Check Sequence) with an integral number of octets
(FCS Error) or a bad FCS with a non-integral octet (Alignment Error) number.
•
Collisions------ Collisions received.
16
•
Utilization------ Percentage of current interface traffic compared to maximum
traffic that the interface can handle.
RMON Events
You can control the occurrences that trigger an alarm and the type of notification that occurs.
•
Events Page------Configures what happens when an alarm is triggered. This can be any
combination of logs and traps.
•
Alarms Page------ Configures the occurrences that trigger an alarm.
To define RMON events:
1. Click System Status > RMON > Events. This page displays previously defined events.
2. Click Add.
3. Enter the parameters.
•
Event Entry Index ------ Displays the event entry index number for the new entry.
•
Community------ Enter the SNMP community string to be included when traps are
sent (optional). Note that the community must be defined using the Defining
SNMPv1,2 Notification Recipients or Defining SNMPv3 Notification Recipients
pages for the trap to reach the Network Management Station.
•
Description------Enter a name for the event. This name is used in the Add RMON
Alarm page to attach an alarm to an event.
•
Notification Type------ Select the type of action that results from this event.
-
-
None------No action occurs when the alarm goes off.
Event Log (Event Log Table)------ Add a log entry to the Event Log table when
the alarm is triggered.
17
-
Trap (SNMP Manager and SYSLOG Server)------ Send a trap to the remote log
server when the alarm goes off.
-
Trap and Event Log------ Add a log entry to the Event Log table and send a
trap to the remote log server when the alarm goes off.
•
Last Event Time------Displays the time of the event. (This is a read-only table in the
parent window and cannot be defined).
•
Owner------Enter the device or user that defined the event.
4. Click Apply. The RMON event is saved to the Running Configuration file.
5. Click Event Log to display the log of alarms that have occurred and that have been logged
(see description below).
RMON Events Logs
The Event Log Table page displays the log of events (actions) that occurred. Two types of
events can be logged: Log or Log and Trap. The action in the event is performed when the
event is bound to an alarm (see the Alarms page) and the conditions of the alarm have
occurred.
1. Click System Status > RMON > Events.
2. Click Event Log.
This page displays the following fields:
•
Event Entry Index ------ Event’s log entry number.
•
Log No.------ Log number (within the event).
•
Log Time------Time that the log entry was entered.
•
Description------Description of event that triggered the alarm.
RMON Alarms
RMON alarms provide a mechanism for setting thresholds and sampling intervals to generate
exception events on counters or any other SNMP object counter maintained by the agent. Both
the rising and falling thresholds must be configured in the alarm. After a rising threshold is
crossed, no rising events are generated until the companion falling threshold is crossed. After a
falling alarm is issued, the next alarm is issued when a rising threshold is crossed.
One or more alarms are bound to an event, which indicates the action to be taken when the alarm
occurs.
Alarm counters can be monitored by either absolute values or changes (delta) in the counter
values.
18
To enter RMON alarms:
1. Click System Status > RMON > Alarms. All previously-defined alarms are displayed. The
fields are described in the Add RMON Alarm page below.
In addition to those fields, the following field appears:
•
Counter Value------ Displays the value of the statistic during the last sampling period.
2. Click Add.
3. Enter the parameters.
•
Alarm Entry Index------Displays the alarm entry number.
•
Interface------Select the type of interface for which RMON statistics are displayed.
•
Counter Name------ Select the MIB variable that indicates the type of occurrence
measured.
•
Sample Type------Select the sampling method to generate an alarm.
The options:
-
Absolute------ If the threshold is crossed, an alarm is generated.
-
Delta------Subtracts the last sampled value from the current value. The
difference in the values is compared to the threshold. If the threshold was
crossed, an alarm is generated.
•
Interval------ Enter the alarm interval time in seconds.
19
•
Startup Alarm------Select the first event from which to start generation of alarms.
Rising is defined by crossing the threshold from a low-value threshold to a highervalue threshold.
-
Rising Alarm------ A rising value triggers the rising threshold alarm.
-
Falling Alarm------A falling value triggers the falling threshold alarm.
-
Rising and Falling Alarm------Both rising and falling values trigger the alarm.
•
Owner------Enter the name of the user or network management system that receives
the alarm.
•
Rising Threshold------Enter the value that triggers the rising threshold alarm.
•
Rising Event------Select an event to be performed when a rising event is triggered.
Events are created in the Events page.
•
Falling Threshold------Enter the value that triggers the falling threshold alarm.
•
Falling Event------ Select an event to be performed when a falling event is triggered.
4. Click Apply. The RMON alarm is saved to the Running Configuration file.
Interface Statistics
The Interface Statistics page displays traffic statistics per port. The refresh rate of the
information can be selected.
This page is useful for analyzing the amount of traffic that is both sent and received and its
dispersion (Unicast, Multicast, and Broadcast).
20
To display Ethernet statistics and/or set the refresh rate:
1. Click System Status > Interface Statistics.
2. Enter the parameters.
•
Interface------Select the specific interface for which
•
Ethernet statistics are to be displayed.
•
Refresh Rate------ Select the time period that passes before the interface
•
Ethernet statistics are refreshed. The available options are as follows:
•
No Refresh------ Statistics are not refreshed.
-
15 Sec------ Statistics are refreshed every 15 seconds.
-
30 Sec------ Statistics are refreshed every 30 seconds.
-
60 Sec------ Statistics are refreshed every 60 seconds.
The Receive Statistics area displays information about incoming packets.
•
Total Octets------Octets received, including bad packets and FCS octets, but excluding
framing bits.
•
Unicast Packets------Good Unicast packets received.
•
Multicast Packets------Good Multicast packets received.
•
Broadcast Packets------Good Broadcast packets received.
•
Error Packets------Packets with errors received.
21
The Transmit Statistics area displays information about outgoing packets.
•
Total Octets------Octets transmitted, including bad packets and FCS octets, but excluding
framing bits.
•
Unicast Packets------Good Unicast packets transmitted.
•
Multicast Packets------Good Multicast packets transmitted.
•
Broadcast Packets------ Good Broadcast packets transmitted.
To clear or view statistics counters, do the following:
•
Click Refresh to refresh the counters on the page.
•
Click Clear to clear the selected interfaces counters.
•
Click View All to see all ports on a single page.
22
Chapter 3 - Quick Start
This section describes how to view device statistics.
To simplify device configuration through quick navigation, the Quick Start page provides links to
the most commonly used pages.
Link Name (on the Page) Linked Page
Configure User Accounts and
Management Access
Configure Device IP Address IPv4 Interface
Create VLANs VLANs
Configure VLAN Memberships VLAN Memberships
Save Your Configuration Configuration File Copy
Clicking on the Support link takes you to the device product support page.
User Access & Accounts
23
Chapter 4 - System Management
This chapter describes the following topics:
•
System Information
•
TCAM Resources
•
Management Session Timeout
•
Time
•
•
SNMP
Logs
System Information
To enter system information:
1. Click Configuration > System Management > System Information.
2. View or modify the system settings.
24
•
System Description------ Displays a description of the device.
•
System Location------Enter the location where the device is physically located.
•
System Contact------ Enter the name of a contact person.
•
System Host Name------Select the host name of this device, which is used in the
prompt of CLI commands.
-
Default------ The default host name (System Name) of these switches is
switch123456, where 123456 represents the last three bytes of the
device MAC address in hex format.
-
User Defined------ Enter the host name. Use only letters, digits, and hyphens.
Host names cannot begin or end with a hyphen. No other symbols,
punctuation characters, or blank spaces are permitted (as specified in
RFC1033, 1034, 1035).
3. Click Apply to save the values in the Running Configuration file.
TCAM Resources
The TCAM Resources page is only displayed in Layer 3 mode.
TCAM holds the rules produced by applications, such as Access Control Lists (ACLs), Quality of
Service (QoS), IP Routing and user-created rules.
Some applications reserve TCAM resources that will be required upon their initiation. Additionally,
processes that initialize during system boot might configure some rules during the startup
process.
25
To configure and view TCAM utilization:
1. Click Configuration > System Management > TCAM Resources.
2. Select one of the following options:
•
Use Default------Use the system value for this field.
•
User Defined------ Enter the maximum number of TCAM entries that you determine
will be used for IPv4 routing.
Counters are displayed for TCAM utilization.
•
IPv4 Hosts
-
Count------Number of IPv4 interfaces configured on the switch.
-
TCAM Entries------Number of TCAM entries currently used by the known IPv4 nodes.
•
IPv4 Interfaces
-
Count------Number of IPv4 interfaces configured on the switch.
-
TCAM Entries------Number of TCAM entries used by the configured IPv4 interfaces.
•
IPv4 Routes
-
Count------Number of known IP routes on the switch.
-
TCAM Entries------Number of TCAM entries currently used by the known IP routes.
•
Total------Total number of TCAM entries.
26
Counters are displayed for Non-IP TCAM Usage:
•
Non-IP
-
In Use------ Number of TCAM entries currently used by applications and features,
excluding IP routing.
-
Maximum Allocated------ Number of available TCAM entries that can be used by
applications and features, excluding IP routing.
Management Session Timeout
The Management Session Timeout configures the time intervals that the management sessions
can remain idle before they timeout and you must log in again to reestablish the session.
To set the idle session timeout for various types of sessions:
1. Click Configuration > System Management > Management Session Timeout.
2. Select the timeout for the following sessions from the corresponding list. The default
timeout value is 10 minutes.
•
Console Session Timeout------ Select the timeout for a console session.
•
Telnet Session Timeout------ Select the timeout for a Telnet session.
27
•
HTTP Session Timeout------Select the timeout for an HTTP session.
•
HTTPs Session Timeout------ Select the timeout for an HTTPS session.
3. Click Apply to set the configuration settings on the device.
Time
This section describes the options for configuring the system time, time zone, and
Daylight Savings Time (DST).
•
Overview
•
System Time
•
SNTP Unicast Server
•
SNTP Multicast/Anycast
Overview
Synchronized system clocks provide a frame of reference between all devices on the network.
Network time synchronization is critical because every aspect of managing, securing, planning,
and debugging a network involves determining when events occur. Without synchronized clocks,
accurately correlating log files between devices when tracking security breaches or network
usage is impossible.
Synchronized time also reduces confusion in shared file systems, as it is important for the
modification times to be consistent, regardless of the machine on which the file systems reside.
For these reasons, it is important that the time configured on all of the devices on the network is
accurate.
Note—The device supports Simple Network Time Protocol (SNTP) and when enabled, the device
dynamically synchronizes the device time with time from an SNTP server. The device operates
only as an SNTP client, and cannot provide time services to other devices.
System Time
System time can be set manually by the user, dynamically from an SNTP server, or synchronized
from the PC running the GUI. If an SNTP server is chosen, the manual time settings are
overwritten when communications with the server are established.
28
As part of the boot process, the device always configures the time, time zone, and DST. These
parameters are obtained from the PC running the GUI, SNTP, values set manually, or if all else
fails, from the factory defaults.
Time
The following methods are available for setting the system time on the device:
•
Manual------User must manually set the time.
•
SNTP------ Time can be received from SNTP time servers. SNTP ensures accurate
network time synchronization of the device up to the millisecond by using an SNTP
server for the clock source. When specifying an SNTP server, if choosing to
identify it by hostname, three suggestions are given in the GUI:
-
time-a.timefreq.bldrdoc.gov
-
time-b.timefreq.bldrdoc.gov
-
time-c.timefreq.bldrdoc.gov
After the time has been set by any of the above sources, it is not set again by the browser.
Note—SNTP is the recommended method for time setting.
Time Zone and Daylight Savings Time (DST)
The Time Zone and DST can be set on the device in the following ways:
•
Dynamic configuration of the device through a DHCP server, where:
-
Dynamic DST, when enabled and available, always takes precedence over
the manual configuration of DST.
-
If the server supplying the source parameters fails, or dynamic
configuration is disabled by the user, the manual settings are used.
-
Dynamic configuration of the time zone and DST continues after the IP
address lease time has expired.
•
Manual configuration of the time zone and DST becomes the Operational time
zone and DST, only if the dynamic configuration is disabled or fails.
Note------ The DHCP server must supply DHCP option 100 in order for dynamic
time zone configuration to take place.
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SNTP Modes
The device can receive system time from an SNTP server in one of the following ways:
•
•
The device supports having all of the above modes active at the same time and selects the
best system time received from an SNTP server, according to an algorithm based on the
closest stratum (distance from the reference clock).
System Time
Client Broadcast Reception (passive mode)------ SNTP servers broadcast the time,
and the device listens to these broadcasts. When the device is in this mode, there
is no need to define a Unicast SNTP server.
Client Broadcast Transmission (active mode)------ The device, as an SNTP client,
periodically requests SNTP time updates. This mode works in either of the
following ways:
-
SNTP Anycast Client Mode------ The device broadcasts time request packets
to all SNTP servers in the subnet, and waits for a response.
-
Unicast SNTP Server Mode------ The device sends Unicast queries to a list of
manually-configured SNTP servers, and waits for a response.
Use the System Time page to select the system time source. If the source is manual, you
can enter the time here.
Caution------ If the system time is set manually and the device is rebooted, the manual time
settings must be reentered.
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