H3C S3600 Series Operation Manual

Operation Manual – NTP H3C S3600 Series Ethernet Switches-Release 1510 Table of Contents

Table of Contents

Chapter 1 NTP Configuration.......................................................................................................1-1

1.1 Introduction to NTP............................................................................................................1-1

1.1.1 Applications of NTP................................................................................................. 1-1

1.1.2 Implementation Principle of NTP.............................................................................1-2

1.1.3 NTP Implementation Modes....................................................................................1-4

1.2 Configuring NTP Implementation Modes...........................................................................1-6

1.2.1 Configuration Prerequisites..................................................................................... 1-6

1.2.2 Configuration Procedure......................................................................................... 1-7

1.3 Configuring Access Control Right...................................................................................... 1-9

1.4 Configuring NTP Authentication ........................................................................................ 1-9

1.4.1 Configuration Prerequisites................................................................................... 1-10

1.4.2 Configuration Procedure....................................................................................... 1-10

1.5 Configuring Optional NTP Parameters............................................................................ 1-12

1.6 Displaying and Debugging NTP.......................................................................................1-13

1.7 Configuration Example .................................................................................................... 1-13

1.7.1 Configuring NTP Server Mode..............................................................................1-13

1.7.2 Configuring NTP Peer Mode.................................................................................1-15

1.7.3 Configuring NTP Broadcast Mode........................................................................1-16

1.7.4 Configuring NTP Multicast Mode.......................................................................... 1-19

1.7.5 Configuring NTP Server Mode with Authentication...............................................1-21

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Operation Manual – NTP H3C S3600 Series Ethernet Switches-Release 1510 Chapter 1

Chapter 1 NTP Configuration

1.1 Introduction to NTP

Network time protocol (NTP) is a time synchronization protocol defined in RFC1305. It is used for time synchronization between a set of distributed time servers and clients. NTP transmits packets through UDP port 123.

NTP is intended for time synchronization between all devices that have clocks in a network so that the clocks of all devices can keep consistent. Thus, the devices can provide multiple unified-time-based applications.

A local system running NTP can not only be synchronized by other clock sources, but also serve as a clock source to synchronize other clocks. Besides, it can synchronize, or be synchronized by other systems by exchanging NTP p ackets.

NTP Configuration

1.1.1 Applications of NTP

NTP is mainly applied to synchronizing the clocks of all devices in a network. For example:

z In network management, the analysis of the log information and debugging

information collected from different devices is meaningful and valid only when network devices that generate the information adopts the same time.

z The billing system requires that the clocks of all network devices be consistent. z Some functions, such as restarting all network devices in a network

simultaneously require that they adopt the same time.

z When multiple systems cooperate to handle a rather complex transaction, they

must adopt the same time to ensure a correct execution order.

z To perform incremental backup operations between a backup server and a host,

you must make sure they adopt the same time.

As setting the system time manually in a network with many devices leads to a lot of workload and cannot ensure the accuracy, it is unfeasible for an administrator to perform the operation. However, an administrator can synchronize the clocks of devices in a network with required accuracy by performing NTP configuration.

NTP has the following advantages:

z Defining the accuracy of clocks by stratum to synchronize the clocks of all devices

in a network quickly

z Supporting access control and MD5 authentication z Sending protocol packets in unicast, multicast, or broadcast mode

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Operation Manual – NTP H3C S3600 Series Ethernet Switches-Release 1510 Chapter 1

 Note:

z The clock stratum determines the accuracy, which ranges from 1 to 16. The stratum

of a reference clock ranges from 1 to 15. The clock accuracy decreases as the stratum number increases. A s tratum 16 clock is in the uns ynchronized state and cannot serve as a reference clock.

z The local clock of an S3600 Ethernet switch cannot operate as a reference clock. It

can serve as a NTP server only after synchronized.

1.1.2 Implementation Principle of NTP

Figure 1-1 shows the implementation principle of NTP. Ethernet switch A (LS_A) is connected to Ethernet switch B (LS_B) through Ethernet

ports. Both have their own system clocks, and they need to synchronize the clocks of each other through NTP. To help you to understand the implementation principle, we suppose that:

NTP Configuration

z Before the system clocks of LS_A and LS_B are synchronized, the clock of LS_A

is set to 10:00:00 am, and the clock of LS_B is set to 11:00:00 am.

z LS_B serves as the NTP server, that is, the clock of LS_A will be synchronized to

that of LS_B.

z It takes one second to transfer an NTP packet from LS_A to LS_B or from LS_A to

LS_B.

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Operation Manual – NTP H3C S3600 Series Ethernet Switches-Release 1510 Chapter 1

NTP Configuration

NTP packet

NTP Packet

1.

2.

3.

4.

LS_A

NTP Packet received at 10:00:03

NTP Packet received at 10:00:03 am

NTP Packet received at 10:00:03

NTP Packet received at 10:00:03 am

NTP Packet received at 10:00:03

NTP Packet received at 10:00:03 am

NTP Packet received at 10:00:03

NTP packet received at 10:00:03 am

LS_A

10:00:00 am

10:00:00am

NTP packet

NTP Packet

Network

NTP packet 10:00:00 am

NTP Packet10:00:00am

NTP Packet10:00:00 am

NTP Packet10:00:00am

NTP Packet 10:00:00 am

NTP Packet10:00:00am

NTP Packet10:00:00 am

NTP Packet10:00:00am

Network

10:00:00 am11:00:01 am11:00:02 am

10:00:00am 11:00:01am 11:00:02am

10:00:00 am11:00:01 am 11:00:02 am

10:00:00am 11:00:01am 11:00:02am

10:00:00 am11:00:01 am11:00:02 am

10:00:00am 11:00:01am 11:00:02am

10:00:00 am11:00:01 am 11:00:02 am

10:00:00am 11:00:01am 11:00:02am

Network

Figure 1-1 Implementation principle of NTP

_B

LS

LS_B

11:00:01 am

11:00:01am

11:00:01 am

11:00:01am

11:00:01 am

11:00:01am

11:00:01 am

11:00:01am

LS

_B

LS

LSLS_B

LS

_B

LSLS_B

LS

_B

LS_B

_B

LS_B

The procedure of synchronizing the system clock is as follows:

z LS_A sends an NTP packet to LS_B, with a timestamp 10:00:00 am (T

1

identifying when it is sent.

z When the packet arrives at LS_B, LS_B inserts its own timestamp 11:00:01 am (T

into the packet.

z When the NTP packet leaves LS_B, LS_B inserts its own timestamp 11:00:02 am

) into the packet.

(T

3

z When receiving a response packet, LS_A inserts a new timestamp 10:00:03 am

) into it.

(T

4

At this time, LS_A has enough information to calculate the following two parameters:

z Delay for an NTP packet to make a round trip between LS_A and LS_B:

Delay = (T

z Time offset of LS_A relative to LS_B:

Offset = ((T

-T1)-(T3 -T2).

4

) + (T3 -T4))/2.

2 -T1

LS_A can then set its own clock according to the above information to synchronize its clock to that of LS_B.

For detailed information, refer to RFC1305.

)

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Operation Manual – NTP

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H3C S3600 Series Ethernet Switches-Release 1510 Chapter 1

1.1.3 NTP Implementation Modes

According to the network structure and the position of the local Ethernet switch in the network, the local Ethernet switch can work in multiple NTP modes to synchronize the clock.

I. Client/server mode

NTP Configuration

Client Se

Filters and selects

a clocks and

synchronize the local clock to that of the preferred server

Clock synchronization

request packet

Response packet

Figure 1-2 Client/sever mode

II. Peer mode

Active peer

In peer mode, both

sides can be

synchronized to each

other

Clock synchronization

Network

NetworkNetworkNetwork

NetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetwork

NetworkNetworkNetworkNetworkNetworkNetworkNetworkNetworkNetwork

NetworkNetwork

request packet

Response pac ket

Synchronize

rver

Works in server mode

automatically and send

a response packet

Pas

sive peer

Works in passive pee

mode automatically

Figure 1-3 Peer mod

e

In the peer mode, the local S3600 Ethernet switch serves as the active peer and sends clock synchronization request packets first, while the remote server serves as the passive peer automatically.

If both of the peers have reference clocks, the one with a smaller stratum number is adopted.

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Operation Manual – NTP H3C S3600 Series Ethernet Switches-Release 1510 Chapter 1

III. Broadcast mode

NTP Configuration

Server

Works in the server

mode automatically and

sends response pack ets

Figure 1-4 Broadcast mod

IV. Multicast mode

Server

Works in the server

mode automatically and

sends response pack ets

Network

NetworkNetwork

Broadcasts clock synchronization

packets periodically

Client/server mode request

Response packet

Broadcasts clock synchronization

packets periodically

e

Network

NetworkNetwork

Multicasts clock synchronization

packets periodically

Client/server mode request

Response packet

Multicasts clock synchronization

packets periodically

Client

Initiates a cl

request after

broadc

Obtains t

client and s

Receives br

Client

Initiates a c

request afte

Obtains t

client and s

Receiv es

he delay between the

the broadc

synchroni

multi

he delay between the

the mult

multicast packets and

synchroni

ient/server mode

receiving the first

ast packet

erver and works in

ast client mode

oadcast packets and zes the local cl ock

lient/server mode r receiving the first cast packet

erver and works in

icast client mode

zes the local clock

Figure 1-5 Multicast mod

e

Table 1-1 describes ho w the above ment ioned NTP modes are impl emented on S3600 series Ethernet switches.

Table 1-1 NTP implementation modes on S3600 series Ethernet switches

NTP

implementation

Configuration on S3600 series switches

mode

Configure the local S3600 Ethernet switch to operate in the

Client/server mode

NTP server mode. In this mode, the remote server serves as the local time server, while the local switch serves as the client.

Configure the local S3600 switch to operate in NTP peer

Peer mode

mode. In this mode, the remote server serves as the peer of the S3600 switch, and the local switch serves as the active peer.

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Operation Manual – NTP H3C S3600 Series Ethernet Switches-Release 1510 Chapter 1

NTP

implementation

Configuration on S3600 series switches

mode

z Configure the local S3600 Ethernet switch to operate in

NTP broadcast server mode. In this mode, the local switch broadcasts NTP packets through the VLAN

Broadcast mode

interface configured on the switch.

z Configure the S3600 switch to operate in NTP broadcast

client mode. In this mode, the local S3600 switch receives broadcast NTP packets through the VLAN interface configured on the switch.

z Configure the local S3600 Ethernet switch to operate in

NTP multicast server mode. In this mode, the local switch sends multicast NTP packets through the VLAN interface

Multicast mode

configured on the switch.

z Configure the local S3600 Ethernet switch to operate in

NTP multicast client mode. In this mode, the local switch receives multicast NTP packets through the VLAN interface configured on the switch.

NTP Configuration

Caution:

An S3600 Ethernet switch can operate in the NTP peer, NTP broadcast server, or NTP multicast server mode only after its clock is synchronized.

1.2 Configuring NTP Implementation Modes

An S3600 Ethernet switch can operate in one of the following NTP modes:

z NTP client mode z NTP server mode z NTP peer mode z NTP broadcast server mode z NTP broadcast client mode z NTP multicast server mode z NTP multicast client mode

1.2.1 Configuration Prerequisites

You need to perform configurations only on the client (or the active peer) when you want an S3600 Ethernet switch to operate in NTP server mode (or NTP peer mode). However, you need to perform configurations on both the server and client when you want the switch to operate in NTP broadcast mode or NTP multicast mode.

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H3C S3600 Series Operation Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

1.1 Introduction to NTP

1.1.1 Applications of NTP

1.1.2 Implementation Principle of NTP

1.1.3 NTP Implementation Modes

I. Client/server mode

II. Peer mode

III. Broadcast mode

IV. Multicast mode

1.2 Configuring NTP Implementation Modes

1.2.1 Configuration Prerequisites