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| Title | Size | Download |
|---|---|---|
| 02-NTP Configuration | 286.58 KB |
Configuring the Operation Modes of NTP
Configuring NTP Client/Server Mode
Configuring NTP Broadcast Mode
Configuring NTP Multicast Mode
Configuring Optional Parameters of NTP
Configuring the Source Interface of NTP Messages
Disabling an Interface from Receiving NTP Messages
Configuring the Maximum Number of Dynamic Sessions Allowed
Configuring Access-Control Rights
Configuring NTP Authentication
Displaying and Maintaining NTP
Configuring NTP Client/Server Mode
Configuring NTP Broadcast Mode
Configuring NTP Multicast Mode
Configuring NTP Client/Server Mode with Authentication
Configuring NTP Broadcast Mode with Authentication
l Support of the H3C WA series WLAN access points (APs) for features may vary by AP model. For more information, see Feature Matrix.
l The interface types and the number of interfaces vary by AP model.
l The term AP in this document refers to common APs, wireless bridges, and mesh APs.
l The models listed in this document are not applicable to all regions. Please consult your local sales office for the models applicable to your region.
This chapter includes these sections:
l Configuring the Operation Modes of NTP
l Configuring Optional Parameters of NTP
l Configuring Access-Control Rights
l Configuring NTP Authentication
l Displaying and Maintaining NTP
NTP Overview
Defined in RFC 1305, the Network Time Protocol (NTP) synchronizes timekeeping among distributed time servers and clients. NTP runs over the User Datagram Protocol (UDP), using UDP port 123.
The purpose of using NTP is to keep consistent timekeeping among all clock-dependent devices within the network so that the devices can provide diverse applications based on the consistent time.
For a local system running NTP, its time can be synchronized by other reference sources and can be used as a reference source to synchronize other clocks.
Applications of NTP
An administrator can by no means keep time synchronized among all the devices within a network by changing the system clock on each station, because this is a huge amount of workload and cannot guarantee the clock precision. NTP, however, allows quick clock synchronization within the entire network while it ensures a high clock precision.
NTP is used when all devices within the network must be consistent in timekeeping, for example:
l In analysis of the log information and debugging information collected from different devices in network management, time must be used as reference basis.
l All devices must use the same reference clock in a charging system.
l To implement certain functions, such as scheduled restart of all devices within the network, all devices must be consistent in timekeeping.
l When multiple systems process a complex event in cooperation, these systems must use that same reference clock to ensure the correct execution sequence.
l For incremental backup between a backup server and clients, timekeeping must be synchronized between the backup server and all the clients.
Advantages of NTP:
l NTP uses a stratum to describe the clock precision, and is able to synchronize time among all devices within the network.
l NTP supports access control and MD5 authentication.
l NTP can unicast, multicast or broadcast protocol messages.
How NTP Works
Figure 1-1 shows the basic workflow of NTP. Device A and Device B are interconnected over a network. They have their own independent system clocks, which need to be automatically synchronized through NTP. For an easy understanding, we assume that:
l Prior to system clock synchronization between Device A and Device B, the clock of Device A is set to 10:00:00 am while that of Device B is set to 11:00:00 am.
l Device B is used as the NTP time server, namely, Device A synchronizes its clock to that of Device B.
l It takes 1 second for an NTP message to travel from one device to the other.
Figure 1-1 Basic work flow of NTP
The process of system clock synchronization is as follows:
l Device A sends Device B an NTP message, which is timestamped when it leaves Device A. The time stamp is 10:00:00 am (T1).
l When this NTP message arrives at Device B, it is timestamped by Device B. The timestamp is 11:00:01 am (T2).
l When the NTP message leaves Device B, Device B timestamps it. The timestamp is 11:00:02 am (T3).
l When Device A receives the NTP message, the local time of Device A is 10:00:03 am (T4).
Up to now, Device A has sufficient information to calculate the following two important parameters:
l The roundtrip delay of NTP message: Delay = (T4–T1) – (T3-T2) = 2 seconds.
l Time difference between Device A and Device B: Offset = ((T2-T1) + (T3-T4))/2 = 1 hour.
Based on these parameters, Device A can synchronize its own clock to the clock of Device B.
This is only a rough description of the work mechanism of NTP. For details, see RFC 1305.
NTP Message Format
NTP uses two types of messages, clock synchronization message and NTP control message. An NTP control message is used in environments where network management is needed. As it is not a must for clock synchronization, it will not be discussed in this document.
All NTP messages mentioned in this document refer to NTP clock synchronization messages.
A clock synchronization message is encapsulated in a UDP message, in the format shown in Figure 1-2.
Figure 1-2 Clock synchronization message format
Main fields are described as follows:
l LI: 2-bit leap indicator. When set to 11, it warns of an alarm condition (clock unsynchronized); when set to any other value, it is not to be processed by NTP.
l VN: 3-bit version number, indicating the version of NTP. The latest version is version 3.
l Mode: a 3-bit code indicating the work mode of NTP. This field can be set to these values: 0 – reserved; 1 – symmetric active; 2 – symmetric passive; 3 – client; 4 – server; 5 – broadcast or multicast; 6 – NTP control message; 7 – reserved for private use.
l Stratum: an 8-bit integer indicating the stratum level of the local clock, with the value ranging from 1 to 16. The clock precision decreases from stratum 1 through stratum 16. A stratum 1 clock has the highest precision, and a stratum 16 clock is not synchronized and cannot be used as a reference clock.
l Poll: 8-bit signed integer indicating the poll interval, namely the maximum interval between successive messages.
l Precision: an 8-bit signed integer indicating the precision of the local clock.
l Root Delay: roundtrip delay to the primary reference source.
l Root Dispersion: the maximum error of the local clock relative to the primary reference source.
l Reference Identifier: Identifier of the particular reference source.
l Reference Timestamp: the local time at which the local clock was last set or corrected.
l Originate Timestamp: the local time at which the request departed from the client for the service host.
l Receive Timestamp: the local time at which the request arrived at the service host.
l Transmit Timestamp: the local time at which the reply departed from the service host for the client.
l Authenticator: authentication information.
Operation Modes of NTP
Devices running NTP can implement clock synchronization in one of the following modes:
l Client/server mode
l Broadcast mode
l Multicast mode
You can select operation modes of NTP as needed. In case that the IP address of the NTP server is unknown and many devices in the network need to be synchronized, you can adopt the broadcast or multicast mode; in the client/server mode, a device is synchronized from the specified server, and thus clock reliability is enhanced.
Client/server mode
Figure 1-3 Client/server mode
When working in the client/server mode, a client sends a clock synchronization message to servers, with the Mode field in the message set to 3 (client mode). Upon receiving the message, the servers automatically work in the server mode and send a reply, with the Mode field in the messages set to 4 (server mode). Upon receiving the replies from the servers, the client performs clock filtering and selection, and synchronizes its local clock to that of the optimal reference source.
In this mode, a client can be synchronized to a server, but not vice versa.
Broadcast mode
Figure 1-4 Broadcast mode
In the broadcast mode, a server periodically sends clock synchronization messages to the broadcast address 255.255.255.255, with the Mode field in the messages set to 5 (broadcast mode). Clients listen to the broadcast messages from servers. After a client receives the first broadcast message, the client and the server start to exchange messages, with the Mode field set to 3 (client mode) and 4 (server mode) to calculate the network delay between the client and the server. Then, the client enters the broadcast client mode and continues listening to broadcast messages, and synchronizes its local clock based on the received broadcast messages.
Multicast mode
Figure 1-5 Multicast mode
In the multicast mode, a server periodically sends clock synchronization messages to the user-configured multicast address, or, if no multicast address is configured, to the default NTP multicast address 224.0.1.1, with the Mode field in the messages set to 5 (multicast mode). Clients listen to the multicast messages from servers. After a client receives the first multicast message, the client and the server start to exchange messages, with the Mode field set to 3 (client mode) and 4 (server mode) to calculate the network delay between client and the server. Then, the client enters the multicast client mode and continues listening to multicast messages, and synchronizes its local clock based on the received multicast messages.
In broadcast mode and multicast mode, the client and the server can work in the specified NTP working mode only after they exchange NTP messages with the Mode field being 3 (client mode) and the Mode field being 4 (server mode). During this message exchange process, NTP clock synchronization can be implemented.
NTP Configuration Task List
Complete the following tasks to configure NTP:
|
Task |
Remarks |
|
Required |
|
|
Optional |
|
|
Optional |
|
|
Optional |
Configuring the Operation Modes of NTP
APs can implement clock synchronization in one of the following modes:
l Client/server mode
l Broadcast mode
l Multicast mode
For the client/server mode, you need to configure only clients; for the broadcast or multicast mode, you need to configure both servers and clients.
A single AP can have a maximum of 128 associations at the same time, including static associations and dynamic associations. A static association refers to an association that a user has manually created by using an NTP command, while a dynamic association is a temporary association created by the system during operation. A dynamic association will be removed if the system fails to receive messages from it over a specific long time. In the client/server mode, for example, when you carry out a command to synchronize the time to a server, the system will create a static association, and the server will just respond passively upon the receipt of a message, rather than creating an association (static or dynamic). In the broadcast or multicast mode, static associations will be created at the server side, and dynamic associations will be created at the client side.
Configuring NTP Client/Server Mode
For APs working in the client/server mode, you only need to make configurations on the clients, but not on the servers.
Follow these steps to configure an NTP client:
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Specify an NTP server for the AP |
ntp-service unicast-server { ip-address | server-name } [ authentication-keyid keyid | priority | source-interface interface-type interface-number | version number ] * |
Required No NTP server is specified by default. |
l In the ntp-service unicast-server command, ip-address must be a unicast address, rather than a broadcast address, a multicast address or the IP address of the local clock.
l When the source interface of the NTP packets is specified by the source-interface argument, the source IP address of the NTP packets will be configured as the primary IP address of the specified interface.
l An AP can act as a server to synchronize the clock of other APs only after its clock has been synchronized. If the clock of a server has a stratum level higher than or equal to that of a client’s clock, the client does not synchronize its clock to the server’s.
l You can configure multiple servers by repeating the ntp-service unicast-server command. The clients does choose the optimal reference source according to the clock priorities..
Configuring NTP Broadcast Mode
A broadcast server periodically sends NTP broadcast messages to the broadcast address 255.255.255.255. After receiving the messages, an AP working in NTP broadcast client mode sends a reply and synchronizes its local clock.
For APs working in the broadcast mode, you need to configure both the servers and clients. Because an interface needs to be specified on a broadcast server for sending NTP broadcast messages and an interface also needs to be specified on each broadcast client for receiving broadcast messages, the NTP broadcast mode can be configured only in the specific interface view.
Configuring a broadcast client
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Enter interface view |
interface interface-type interface-number |
Required Enter the interface used to receive NTP broadcast messages. |
|
Configure the AP to work in the NTP broadcast client mode |
ntp-service broadcast-client |
Required |
Configuring a broadcast server
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Enter interface view |
interface interface-type interface-number |
Enter the interface used to send NTP broadcast messages. |
|
Configure the AP to work in the NTP broadcast server mode |
ntp-service broadcast-server [ authentication-keyid keyid | version number ] * |
Required |
Configuring NTP Multicast Mode
A multicast server periodically sends NTP multicast messages to multicast clients, which send replies after receiving the messages and synchronize their local clocks.
For APs working in the multicast mode, you need to configure both the servers and clients. The NTP multicast mode must be configured in the specific interface view.
Configuring a multicast client
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Enter interface view |
interface interface-type interface-number |
Enter the interface used to receive NTP multicast messages. |
|
Configure the AP to work in the NTP multicast client mode |
ntp-service multicast-client [ ip-address ] |
Required |
Configuring a multicast server
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Enter interface view |
interface interface-type interface-number |
Enter the interface used to send NTP multicast message. |
|
Configure the AP to work in the NTP multicast server mode |
ntp-service multicast-server [ ip-address ] [ authentication-keyid keyid | ttl ttl-number | version number ] * |
Required |
A multicast server can synchronize broadcast clients only after its clock has been synchronized.
Configuring Optional Parameters of NTP
Configuring the Source Interface of NTP Messages
If you specify the source interface of NTP messages, the AP sets the source IP address of the NTP messages as the primary IP address of the specified interface when sending the NTP messages.
When the AP responds to the NTP request received, the source IP address of the NTP response is always the IP address of the interface that received the NTP request.
Following these steps to configure the source interface of NTP messages:
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Configure the source interface of NTP messages |
ntp-service source-interface interface-type interface-number |
Required By default, no source interface is specified for NTP messages, and the system uses the IP address of the interface determined by the matching route as the source IP address of NTP messages. |
l If you have specified a source interface of NTP messages in the ntp-service unicast-server command, the interface specified in the ntp-service unicast-server command serves as the source interface of NTP messages.
l If you have configured the ntp-service broadcast-server or ntp-service multicast-server command, the source interface of the broadcast or multicast NTP messages is the interface configured with the respective command.
l If the specified source interface for NTP messages is down, the source IP address for an NTP message that is sent out is the primary IP address of the outgoing interface of the NTP message.
Disabling an Interface from Receiving NTP Messages
When NTP is enabled, NTP messages can be received from all the interfaces by default, and you can disable an interface from receiving NTP messages through the following configuration.
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Enter interface view |
interface interface-type interface-number |
— |
|
Disable the interface from receiving NTP messages |
ntp-service in-interface disable |
Required An interface is enabled to receive NTP messages by default. |
Configuring the Maximum Number of Dynamic Sessions Allowed
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Configure the maximum number of dynamic sessions allowed to be established locally |
ntp-service max-dynamic-sessions number |
Required 100 by default |
Configuring Access-Control Rights
With the following command, you can configure the NTP service access-control right to the local AP. There are four access-control rights, as follows:
l query: control query permitted. This level of right permits the peer AP to perform control query to the NTP service on the local AP but does not permit the peer AP to synchronize its clock to the local AP. The so-called “control query” refers to query of some states of the NTP service, including alarm information, authentication status, clock source information, and so on.
l synchronization: server access only. This level of right permits the peer AP to synchronize its clock to the local AP but does not permit the peer AP to perform control query.
l server: server access and query permitted. This level of right permits the peer AP to perform synchronization and control query to the local AP but does not permit the local AP to synchronize its clock to the peer AP.
l peer: full access. This level of right permits the peer AP to perform synchronization and control query to the local AP and also permits the local AP to synchronize its clock to the peer AP.
From the highest NTP service access-control right to the lowest one are peer, server, synchronization, and query. When an AP receives an NTP request, it will perform an access-control right match and will use the first matched right.
Configuration Prerequisites
Prior to configuring the NTP service access-control right to the local AP, you need to create and configure an ACL associated with the access-control right. For more information about the ACL, see ACL in the ACL and QoS Configuration Guide.
Configuration Procedure
Follow these steps to configure the NTP service access-control right to the local AP:
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Configure the NTP service access-control right for a peer AP to access the local AP |
ntp-service access { peer | query | server | synchronization } acl-number |
Required peer by default. |
Configuring NTP Authentication
Configuration Prerequisites
The configuration of NTP authentication involves configuration tasks to be implemented on the client and on the server.
When configuring the NTP authentication feature, pay attention to the following principles:
l For all synchronization modes, when you enable the NTP authentication feature, you should configure an authentication key and specify it as a trusted key. Namely, the ntp-service authentication enable command must work together with the ntp-service authentication-keyid command and the ntp-service reliable authentication-keyid command. Otherwise, the NTP authentication function cannot be normally enabled.
l For the client/server mode, you need to associate the specified authentication key on the client with the corresponding NTP server. Otherwise, the NTP authentication feature cannot be normally enabled.
l For the broadcast server mode or multicast server mode, you need to associate the specified authentication key on the broadcast server or multicast server with the corresponding NTP server. Otherwise, the NTP authentication feature cannot be normally enabled.
l For the client/server mode, if the NTP authentication feature has not been enabled for the client, the client can synchronize with the server regardless of whether the NTP authentication feature has been enabled for the server or not. If the NTP authentication is enabled on a client, the client can be synchronized only to a server that can provide a trusted authentication key.
l For all synchronization modes, the server side and the client side must be consistently configured.
Configuration Procedure
Configuring NTP authentication for a client
Follow these steps to configure NTP authentication for a client:
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Enable NTP authentication |
ntp-service authentication enable |
Required Disabled by default |
|
Configure an NTP authentication key |
ntp-service authentication-keyid keyid authentication-mode md5 value |
Required No NTP authentication key by default |
|
Configure the key as a trusted key |
ntp-service reliable authentication-keyid keyid |
Required No authentication key is configured to be trusted by default. |
|
Associate the specified key with an NTP server |
Client/server mode: ntp-service unicast-server { ip-address | server-name } authentication-keyid keyid |
Required You can associate a non-existing key with an NTP server. To enable NTP authentication, you must configure the key and specify it as a trusted key after associating the key with the NTP server. |
After you enable the NTP authentication feature for the client, make sure that you configure for the client an authentication key that is the same as on the server and specify that the authentication key is trusted; otherwise, the client cannot be synchronized to the server.
Configuring NTP authentication for a server
Follow these steps to configure NTP authentication for a server:
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Enable NTP authentication |
ntp-service authentication enable |
Required Disabled by default |
|
Configure an NTP authentication key |
ntp-service authentication-keyid keyid authentication-mode md5 value |
Required No NTP authentication key by default |
|
Configure the key as a trusted key |
ntp-service reliable authentication-keyid keyid |
Required No authentication key is configured to be trusted by default. |
|
Enter interface view |
interface interface-type interface-number |
— |
|
Associate the specified key with an NTP server |
Broadcast server mode: ntp-service broadcast-server authentication-keyid keyid |
Required You can associate a non-existing key with an NTP server. To enable NTP authentication, you must configure the key and specify it as a trusted key after associating the key with the NTP server. |
|
Multicast server mode: ntp-service multicast-server authentication-keyid keyid |
The procedure of configuring NTP authentication on a server is the same as that on a client, and the same authentication key must be configured on both the server and client sides.
Displaying and Maintaining NTP
|
To do… |
Use the command… |
Remarks |
|
View the information of NTP service status |
display ntp-service status |
Available in any view |
|
View the information of NTP sessions |
display ntp-service sessions [ verbose ] |
Available in any view |
|
View the brief information of the NTP servers from the local AP back to the primary reference source |
display ntp-service trace |
Available in any view |
NTP Configuration Examples
Unless otherwise specified, the examples given in this section apply to all access points that support NTP.
Configuring NTP Client/Server Mode
Network requirements
l As shown in Figure 1-6, the local clock of Device is to be used as a reference source, with the stratum level of 2.
l AP works in the client/server mode and Device is to be used as the NTP server of AP.
Figure 1-6 Network diagram for NTP client/server mode configuration
Configuration procedure
1) Configuration on Device:
# Specify the local clock as the reference source, with the stratum level of 2.
<Device> system-view
[Device] ntp-service refclock-master 2
2) Configuration on AP:
# View the NTP status of AP before clock synchronization.
<AP> display ntp-service status
Clock status: unsynchronized
Clock stratum: 16
Reference clock ID: none
Nominal frequency: 64.0000 Hz
Actual frequency: 64.0000 Hz
Clock precision: 2^7
Clock offset: 0.0000 ms
Root delay: 0.00 ms
Root dispersion: 0.00 ms
Peer dispersion: 0.00 ms
Reference time: 00:00:00.000 UTC Jan 1 1900 (00000000.00000000)
# Specify Device as the NTP server of AP so that AP is synchronized to Device.
<AP> system-view
[AP] ntp-service unicast-server 1.0.1.11
# View the NTP status of AP after clock synchronization.
[AP] display ntp-service status
Clock status: synchronized
Clock stratum: 3
Reference clock ID: 1.0.1.11
Nominal frequency: 64.0000 Hz
Actual frequency: 64.0000 Hz
Clock precision: 2^7
Clock offset: 0.0000 ms
Root delay: 31.00 ms
Root dispersion: 1.05 ms
Peer dispersion: 7.81 ms
Reference time: 14:53:27.371 UTC Sep 19 2005 (C6D94F67.5EF9DB22)
The output shows that AP has been synchronized to Device, and the clock stratum level of AP is 3, while that of Device is 2.
# View the NTP session information of AP, which shows that an association has been set up between AP and Device.
[AP] display ntp-service sessions
source reference stra reach poll now offset delay disper
**************************************************************************
[12345] 1.0.1.11 127.127.1.0 2 63 64 3 -75.5 31.0 16.5
note: 1 source(master),2 source(peer),3 selected,4 candidate,5 configured
Total associations : 1
Configuring NTP Broadcast Mode
Network requirements
l As shown in Figure 1-7, Switch B’s local clock is to be used as a reference source, with the stratum level of 2.
l Switch B works in the broadcast server mode and sends out broadcast messages from VLAN-interface 2.
l AP A and AP B work in the broadcast client mode. AP A listens to broadcast messages through its VLAN-interface 3 and AP B from its VLAN-interface 2.
Figure 1-7 Network diagram for NTP broadcast mode configuration
Configuration procedure
1) Configuration on Switch B:
# Specify the local clock as the reference source, with the stratum level of 2.
<Switch B> system-view
[Switch B] ntp-service refclock-master 2
# Configure Switch B to work in the broadcast server mode and send broadcast messages through VLAN-interface 2.
[Switch B] interface vlan-interface 2
[Switch B-Vlan-interface2] ntp-service broadcast-server
2) Configuration on AP B:
# Configure AP B to work in the broadcast client mode and receive broadcast messages on VLAN-interface 2.
<AP B> system-view
[AP B] interface vlan-interface 2
[AP B-Vlan-interface2] ntp-service broadcast-client
3) Configuration on AP A:
# Configure AP A to work in the broadcast client mode and receive broadcast messages on VLAN-interface 3.
<AP A> system-view
[AP A] interface vlan-interface 3
[AP A-Vlan-interface3] ntp-service broadcast-client
Because AP A and Switch B are on different subnets, AP A cannot receive the broadcast messages from Switch B. AP B gets synchronized upon receiving a broadcast message from Switch B.
# View the NTP status of AP B after clock synchronization.
[AP B-Vlan-interface2] display ntp-service status
Clock status: synchronized
Clock stratum: 3
Reference clock ID: 3.0.1.31
Nominal frequency: 64.0000 Hz
Actual frequency: 64.0000 Hz
Clock precision: 2^7
Clock offset: 0.0000 ms
Root delay: 31.00 ms
Root dispersion: 8.31 ms
Peer dispersion: 34.30 ms
Reference time: 16:01:51.713 UTC Sep 19 2005 (C6D95F6F.B6872B02)
The output shows that AP B has been synchronized to Switch B, and the clock stratum level of AP B is 3, while that of Switch B is 2.
# View the NTP session information of AP B, which shows that an association has been set up between AP B and Switch B.
[AP B-Vlan-interface2] display ntp-service sessions
source reference stra reach poll now offset delay disper
**************************************************************************
[1234] 3.0.1.31 127.127.1.0 2 254 64 62 -16.0 32.0 16.6
note: 1 source(master),2 source(peer),3 selected,4 candidate,5 configured
Total associations : 1
Configuring NTP Multicast Mode
Network requirements
l As shown in Figure 1-8, Switch B’s local clock is to be used as a reference source, with the stratum level of 2.
l Switch B works in the multicast server mode and sends out multicast messages from VLAN-interface 2.
l AP A and AP B work in the multicast client mode and receive multicast messages through VLAN-interface 3 and VLAN-interface 2 respectively.
Figure 1-8 Network diagram for NTP multicast mode configuration
Configuration procedure
1) Configuration on Switch B:
# Specify the local clock as the reference source, with the stratum level of 2.
<Switch B> system-view
[Switch B] ntp-service refclock-master 2
# Configure Switch B to work in the multicast server mode and send multicast messages through VLAN-interface 2.
[Switch B] interface vlan-interface 2
[Switch B-Vlan-interface2] ntp-service multicast-server
2) Configuration on AP B:
# Configure AP B to work in the multicast client mode and receive multicast messages on VLAN-interface 2.
<AP B> system-view
[AP B] interface vlan-interface 2
[AP B-Vlan-interface2] ntp-service multicast-client
Because AP B and Switch B are on the same subnet, AP B can receive the multicast messages from Switch B without being configured with the multicast function and can be synchronized to Switch B.
# View the NTP status of AP B after clock synchronization.
[AP B-Vlan-interface2] display ntp-service status
Clock status: synchronized
Clock stratum: 3
Reference clock ID: 3.0.1.31
Nominal frequency: 64.0000 Hz
Actual frequency: 64.0000 Hz
Clock precision: 2^7
Clock offset: 0.0000 ms
Root delay: 31.00 ms
Root dispersion: 8.31 ms
Peer dispersion: 34.30 ms
Reference time: 16:01:51.713 UTC Sep 19 2005 (C6D95F6F.B6872B02)
The output shows that AP B has been synchronized to Switch B, and the clock stratum level of AP B is 3, while that of Switch B is 2.
# View the NTP session information of AP B, which shows that an association has been set up between AP B and Switch B.
[AP B-Vlan-interface2] display ntp-service sessions
source reference stra reach poll now offset delay disper
**************************************************************************
[1234] 3.0.1.31 127.127.1.0 2 254 64 62 -16.0 31.0 16.6
note: 1 source(master),2 source(peer),3 selected,4 candidate,5 configured
Total associations : 1
3) Configuration on Switch A:
Because AP A and Switch B are on different subnets, you must configure the multicast function on Switch A before AP A can receive multicast messages from Switch B.
# Enable IP multicast routing and IGMP.
<Switch A> system-view
[Switch A] multicast routing-enable
[Switch A] interface vlan-interface 2
[Switch A-Vlan-interface2] pim dm
[Switch A-Vlan-interface2] quit
[Switch A] vlan 3
[Switch A-vlan3] port ethernet 1/0/1
[Switch A-vlan3] quit
[Switch A] interface vlan-interface 3
[Switch A-Vlan-interface3] igmp enable
[Switch A-Vlan-interface3] igmp static-group 224.0.1.1
[Switch A-Vlan-interface3] quit
[Switch A] interface ethernet 1/0/1
[Switch A-Ethernet1/0/1] igmp-snooping static-group 224.0.1.1 vlan 3
4) Configuration on AP A:
# Enable IP multicast routing and IGMP.
<AP A> system-view
[AP A] interface vlan-interface 3
# Configure AP A to work in the multicast client mode and receive multicast messages on VLAN-interface 3.
[AP A-Vlan-interface3] ntp-service multicast-client
# View the NTP status of AP A after clock synchronization.
[AP A-Vlan-interface3] display ntp-service status
Clock status: synchronized
Clock stratum: 3
Reference clock ID: 3.0.1.31
Nominal frequency: 64.0000 Hz
Actual frequency: 64.0000 Hz
Clock precision: 2^7
Clock offset: 0.0000 ms
Root delay: 40.00 ms
Root dispersion: 10.83 ms
Peer dispersion: 34.30 ms
Reference time: 16:02:49.713 UTC Sep 19 2005 (C6D95F6F.B6872B02)
The output shows that AP A has been synchronized to Switch B, and the clock stratum level of AP A is 3, while that of Switch B is 2.
# View the NTP session information of AP A, which shows that an association has been set up between AP A and Switch B.
[AP A-Vlan-interface3] display ntp-service sessions
source reference stra reach poll now offset delay disper
**************************************************************************
[1234] 3.0.1.31 127.127.1.0 2 255 64 26 -16.0 40.0 16.6
note: 1 source(master),2 source(peer),3 selected,4 candidate,5 configured
Total associations : 1
Configuring NTP Client/Server Mode with Authentication
Network requirements
l As shown in Figure 1-9, the local clock of Device is to be configured as a reference source, with the stratum level of 2.
l AP works in the client mode and Device is to be used as the NTP server of AP.
l NTP authentication is to be enabled for both Device and AP.
Figure 1-9 Network diagram for configuration of NTP client/server mode with authentication
Configuration procedure
1) Configuration on Device:
# Specify the local clock as the reference source, with the stratum level of 2.
<Device> system-view
[Device] ntp-service refclcok-master 2
2) Configuration on AP:
<AP> system-view
# Enable NTP authentication on AP.
[AP] ntp-service authentication enable
# Set an authentication key.
[AP] ntp-service authentication-keyid 42 authentication-mode md5 aNiceKey
# Specify the key as a trusted key.
[AP] ntp-service reliable authentication-keyid 42
# Specify Device A as the NTP server.
[AP] ntp-service unicast-server 1.0.1.11 authentication-keyid 42
Before AP can synchronize its clock to that of Device, you need to enable NTP authentication for Device.
Perform the following configuration on Device:
# Enable NTP authentication.
[Device] ntp-service authentication enable
# Set an authentication key.
[Device] ntp-service authentication-keyid 42 authentication-mode md5 aNiceKey
# Specify the key as a trusted key.
[Device] ntp-service reliable authentication-keyid 42
At this time, AP can synchronize its clock to that of Device.
# View the NTP status of AP after clock synchronization.
[AP] display ntp-service status
Clock status: synchronized
Clock stratum: 3
Reference clock ID: 1.0.1.11
Nominal frequency: 64.0000 Hz
Actual frequency: 64.0000 Hz
Clock precision: 2^7
Clock offset: 0.0000 ms
Root delay: 31.00 ms
Root dispersion: 1.05 ms
Peer dispersion: 7.81 ms
Reference time: 14:53:27.371 UTC Sep 19 2005 (C6D94F67.5EF9DB22)
The output shows that AP has been synchronized to Device, and the clock stratum level of AP is 3, while that of Device is 2.
# View the NTP session information of AP, which shows that an association has been set up AP and Device.
[AP] display ntp-service sessions
source reference stra reach poll now offset delay disper
**************************************************************************
[12345] 1.0.1.11 127.127.1.0 2 63 64 3 -75.5 31.0 16.5
note: 1 source(master),2 source(peer),3 selected,4 candidate,5 configured
Total associations : 1
Configuring NTP Broadcast Mode with Authentication
Network requirements
l As shown in Figure 1-10, Switch C’s local clock is to be used as a reference source, with the stratum level of 3.
l Switch C works in the broadcast server mode and sends out broadcast messages from VLAN-interface 2.
l AP works in the broadcast client mode and receives broadcast messages through VLAN-interface 2.
l NTP authentication is enabled on both Switch C and AP.
Figure 1-10 Network diagram for configuration of NTP broadcast mode with authentication
Configuration procedure
1) Configuration on Switch C:
# Specify the local clock as the reference source, with the stratum level of 3.
<Switch C> system-view
[Switch C] ntp-service refclock-master 3
# Configure NTP authentication.
[Switch C] ntp-service authentication enable
[Switch C] ntp-service authentication-keyid 88 authentication-mode md5 123456
[Switch C] ntp-service reliable authentication-keyid 88
# Specify Switch C as an NTP broadcast server, and specify an authentication key.
[Switch C] interface vlan-interface 2
[Switch C-Vlan-interface2] ntp-service broadcast-server authentication-keyid 88
2) Configuration on AP:
# Configure NTP authentication.
<AP> system-view
[AP] ntp-service authentication enable
[AP] ntp-service authentication-keyid 88 authentication-mode md5 123456
[AP] ntp-service reliable authentication-keyid 88
# Configure AP to work in the NTP broadcast client mode.
[AP] interface vlan-interface 2
[AP-Vlan-interface2] ntp-service broadcast-client
Now, AP can receive broadcast messages through VLAN-interface 2, and Switch C can send broadcast messages through VLAN-interface 2. Upon receiving a broadcast message from Switch C, AP synchronizes its clock to that of Switch C.
# View the NTP status of AP after clock synchronization.
[AP-Vlan-interface2] display ntp-service status
Clock status: synchronized
Clock stratum: 4
Reference clock ID: 3.0.1.31
Nominal frequency: 64.0000 Hz
Actual frequency: 64.0000 Hz
Clock precision: 2^7
Clock offset: 0.0000 ms
Root delay: 31.00 ms
Root dispersion: 8.31 ms
Peer dispersion: 34.30 ms
Reference time: 16:01:51.713 UTC Sep 19 2005 (C6D95F6F.B6872B02)
The output shows that AP has been synchronized to Switch C, and the clock stratum level of AP is 4, while that of Switch C is 3.
# View the NTP session information of AP, which shows that an association has been set up between AP and Switch C.
[AP-Vlan-interface2] display ntp-service sessions
source reference stra reach poll now offset delay disper
**************************************************************************
[1234] 3.0.1.31 127.127.1.0 3 254 64 62 -16.0 32.0 16.6
note: 1 source(master),2 source(peer),3 selected,4 candidate,5 configured
Total associations : 1
