To protect unused
sockets against attacks by malicious users and improve security, S3100-52P Ethernet
switch provide the following functions:
l
UDP port 123 is opened only when the NTP feature
is enabled.
l
UDP port 123 is closed as the NTP feature is
disabled.
These functions are
implemented as follows:
l
Execute one of ntp-service unicast-server,
ntp-service unicast-peer, ntp-service broadcast-client, ntp-service
broadcast-server, ntp-service multicast-client, and ntp-service
multicast-server commands to enable the NTP feature and open UDP port 123
at the same time.
l
Use the undo form of one of the above six
commands to disable all implementation modes of the NTP feature and close UDP
port 123 at the same time.
1.1.1 display ntp-service sessions
Syntax
display ntp-service sessions [ verbose ]
View
Any view
Parameter
verbose:
Displays detailed NTP session information.
Description
Use the display ntp-service sessions
command to display the information about all the sessions maintained by local NTP
services.
If you do not specify the verbose keyword,
the brief information about all the sessions is displayed.
Caution:
An S3100-52P Ethernet
switch attempts to establish a connection in all NTP implementation modes
except the NTP server mode.
Example
# View the status of all sessions
maintained by NTP services.
<H3C> display ntp-service sessions
source reference stra reach
poll now offset delay disper
********************************************************************
[12345]1.1.1.1 127.127.1.0 3 377
512 178 0.0 40.1 22.8
note: 1 source(master),2
source(peer),3 selected,4 candidate,5 configured
Table 1-1 Description
on the fields of the display ntp-service sessions command
|
Field
|
Description
|
|
source
|
IP address
of the synchronization source
|
|
reference
|
Reference clock ID of the synchronization
source
|
|
stra
|
Stratum of the clock of the synchronization
source
|
|
reach
|
Indicates whether or not the synchronization
source is reachable.
|
|
poll
|
Polling interval in seconds, that is, the
maximum interval between two successive messages
|
|
now
|
Time elapsing since the last NTP packet
is sent
|
|
offset
|
Clock offset
|
|
delay
|
Network delay
|
|
disper
|
Maximum offset of the local clock relative
to the reference clock
|
Syntax
display ntp-service status
View
Any view
Parameter
None
Description
Use the display ntp-service status
command to display the status of NTP services.
Example
# View the status of the local NTP service.
<H3C> display ntp-service
status
Clock status: unsynchronized
Clock stratum: 16
Reference clock ID: none
Nominal frequency: 100.0000 Hz
Actual frequency: 100.0000 Hz
Clock precision: 2^17
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)
Table 1-2 Description on fields of the display ntp-service status
command
|
Field
|
Description
|
|
Clock status
|
Status of the local clock
|
|
Clock stratum
|
Stratum of the local clock
|
|
Reference clock ID
|
Address of the remote server or ID of the
reference clock after the local system is synchronized to a remote NTP server
or a reference clock
|
|
Nominal frequency
|
Nominal frequency of the local clock
|
|
Actual frequency
|
Actual frequency of the local clock
|
|
Clock precision
|
Precision of the local clock
|
|
Clock offset
|
Offset of the local clock relative to the
NTP server
|
|
Root delay
|
Roundtrip delay between the local clock
and the primary reference clock
|
|
Root dispersion
|
Maximum dispersion of the local clock relative
to the primary reference clock
|
|
Peer dispersion
|
Maximum dispersion of the remote NTP
server
|
|
Reference time
|
Reference timestamp
|
Syntax
display ntp-service trace
View
Any view
Parameter
None
Description
Use the display ntp-service trace
command to display the brief information of each NTP time server along the time
synchronization chain from the local device to the reference clock source.
Example
# View the brief information of each NTP
time server along the time synchronization chain from the local device to the
reference clock source.
<H3C> display ntp-service trace
server4: stratum 4, offset 0.0019529,
synch distance 0.144135
server3: stratum 3, offset 0.0124263,
synch distance 0.115784
server2: stratum 2, offset 0.0019298,
synch distance 0.011993
server1: stratum 1, offset 0.0019298,
synch distance 0.011993 refid 'GPS Reciever'
The above information displays the time
synchronization chain of server4: serve4 is synchronized to server3, server3 to
server2, server2 to server1, and server1 to the reference clock source GPS receiver.
Syntax
ntp-service access { peer | server | synchronization | query }
acl-number
undo ntp-service access { peer | server | synchronization | query
}
View
System view
Parameter
peer: Allows
time request and query on the local NTP server. The local clock can also be
synchronized to the remote server.
server: Allows
time request and query on the local NTP server. The local clock cannot be
synchronized to the remote server.
synchronization: Allows only time request on the local NTP server.
query:
Allows only query on the local NTP server.
acl-number: Basic
access control list (ACL) number, in the range of 2000 to 2999.
Description
Use the ntp-service access command
to set the access control right to the local NTP server.
Use the undo ntp-service access
command to remove the configured access control right to the local NTP server.
By default, the access control right to the
local NTP server is peer.
The ntp-service access command only
provides a minimal degree of security measure. A more secure way is to perform
identity authentication.
The right of a received access request is
matched from the highest to the lowest in order of peer, server, synchronization,
and query.
Example
# Configure the peer in ACL 2076 to have the
full access right to the local NTP server, including time request, query
control, and time synchronization.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service access peer 2076
# Configure the peer in ACL 2028 to have
the right to access and query the local NTP server.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service access server 2028
Syntax
ntp-service authentication enable
undo ntp-service authentication enable
View
System view
Parameter
None
Description
Use the ntp-service authentication
enable command to enable the NTP authentication.
Use the undo ntp-service authentication
enable command to disable the NTP authentication.
By default, the NTP authentication is
disabled.
Example
# Enable the NTP authentication.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service authentication
enable
Syntax
ntp-service authentication-keyid key-id authentication-mode md5 value
undo ntp-service authentication-keyid key-id
View
System view
Parameter
key-id: Authentication
key ID, in the range of 1 to 4294967295.
value: Authentication
key, a string comprising 1 to 32 characters. Up to 1024 keys can be configured.
Description
Use the ntp-service authentication-keyid
command to configure an NTP authentication key.
Use the ntp-service authentication-keyid
command to remove an NTP authentication key.
By default, no NTP authentication key is
configured.
Currently, the system only supports the message
digest 5 (MD5) algorithm.
Example
# Configure an MD5 authentication key, with
the key ID being 10 and the key being BetterKey.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service authentication-keyid
10 authentication-mode md5 BetterKey
Syntax
ntp-service broadcast-client
undo ntp-service
broadcast-client
View
VLAN interface view
Parameter
None
Description
Use the ntp-service broadcast-client
command to configure an Ethernet switch to operate in the NTP broadcast client
mode and receive NTP broadcast messages through the current interface.
Use the undo ntp-service
broadcast-client command to remove the configuration.
By default, no switch operates in the broadcast
client mode.
Example
# Configure the switch to operate in the
broadcast client mode and receive NTP broadcast messages through Vlan-interface1.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] interface Vlan-interface1
[H3C-Vlan-interface1] ntp-service
broadcast-client
1.1.8 ntp-service
broadcast-server
Syntax
ntp-service broadcast-server
[ authentication-keyid key-id | version number ]*
undo ntp-service
broadcast-server
View
VLAN interface view
Parameter
authentication-keyid key-id: Specifies the key ID used for sending
messages to broadcast clients. The key-id argument ranges from 1 to 4294967295.
You do not need to configure authentication-keyid key-id if
authentication is not required.
version
number: Specifies the NTP version number which ranges
from 1 to 3. The default version number is 3.
Description
Use the ntp-service broadcast-server
command to configure an Ethernet switch to operate in the NTP broadcast server
mode and send NTP broadcast messages through the current interface.
Use the undo ntp-service broadcast-server
command to remove the configuration.
By default, no Ethernet switch operates in
the NTP broadcast server mode.
Example
# Configure the switch to send NTP
broadcast messages through Vlan-interface1 and use authentication key 4 for
encryption, and set the NTP version number to 3.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] interface Vlan-interface 1
[H3C-Vlan-interface1] ntp-service
broadcast-server authentication-key 4 version 3
Syntax
ntp-service in-interface disable
undo ntp-service in-interface disable
View
VLAN interface view
Parameter
None
Description
Use the ntp-service in-interface disable
command to disable the interface from receiving NTP messages.
Use the undo ntp-service in-interface
disable command to enable the interface to receive NTP messages.
By default, the interface can receive NTP messages.
Example
# Disable Vlan-interface1 from receiving
NTP messages.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] interface Vlan-interface 1
[H3C-Vlan-interface1] ntp-service in-interface
disable
Syntax
ntp-service max-dynamic-sessions number
undo ntp-service max-dynamic-sessions
View
System view
Parameter
number: Maximum
number of the NTP sessions that can be established locally. This argument ranges
from 0 to 100.
Description
Use the ntp-service max-dynamic-sessions
command to set the maximum number of NTP sessions that can be established
locally.
Use the undo ntp-service
max-dynamic-sessions command to restore the default.
By default, up to 100 dynamic NTP sessions
can be established locally.
Example
# Set the maximum number of dynamic NTP
sessions that can be established locally to 50.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service max-dynamic-sessions
50
Syntax
ntp-service multicast-client
[ ip-address ]
undo ntp-service multicast-client [ ip-address ]
View
VLAN interface view
Parameter
ip-address:
Multicast IP address, in the range of 224.0.1.1 to 224.0.1.255. The default IP
address is 224.0.1.1.
Description
Use the ntp-service multicast-client
command to configure an Ethernet switch to operate in the NTP multicast client
mode and receive NTP multicast messages through the current interface.
Use the undo ntp-service
multicast-client command to remove the configuration.
By default, no Ethernet switch operates in the
NTP multicast client mode.
Example
# Configure the switch to receive NTP
multicast messages through Vlan-interface1, with the multicast IP address being
224.0.1.1.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] interface Vlan-interface 1
[H3C-Vlan-interface1] ntp-service
multicast-client 224.0.1.1
Syntax
ntp-service multicast-server
[ ip-address ] [ authentication-keyid key-id | ttl ttl-number
| version number ]*
undo ntp-service multicast-server [ ip-address ]
View
VLAN interface view
Parameter
ip-address:
Multicast IP address, which defaults to 224.0.1.1.
authentication-keyid key-id: Specifies the key ID used for
sending messages to multicast clients. The key-id argument ranges from 1
to 4294967295.
ttl
ttl-number: Defines the lifetime of multicast messages.
The ttl-number argument ranges from 1 to 255 and defaults to 16.
version
number: Specifies the NTP version number which
ranges from 1 to 3 and defaults to 3.
Description
Use the ntp-service multicast-server
command to configure an Ethernet switch to operate in the NTP multicast server
mode and send NTP multicast messages through the current interface.
Use the undo ntp-service multicast-server
command to remove the configuration.
By default, no Ethernet switch operates in
multicast server mode.
Example
# Configure the switch to send NTP
multicast messages through Vlan-interface1, and set the multicast group address
to 224.0.1.1, keyid to 4, and the NTP version number to 3.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] interface Vlan-interface 1
[H3C-Vlan-interface1]ntp-service
multicast-server 224.0.1.1
authentication-keyid 4 version 3
Syntax
ntp-service reliable
authentication-keyid key-id
undo ntp-service reliable
authentication-keyid key-id
View
System view
Parameter
key-id: Authentication
key ID, in the range of 1 to 4294967295.
Description
Use the ntp-service reliable
authentication-keyid command to specify an authentication key as a trusted
key.
If authentication is enabled, a client can only
be synchronized to a server that can provide a trusted key.
Use the undo ntp-service reliable
authentication-keyid command to remove the configuration.
By default, no trusted authentication key
is configured.
Example
# Enable NTP authentication. The encryption
algorithm is MD5, the key ID is 37, and the trusted key is BetterKey.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service authentication
enable
[H3C] ntp-service authentication-keyid
37 authentication-mode md5 BetterKey
[H3C] ntp-service reliable
authentication-keyid 37
Syntax
ntp-service source-interface Vlan-interface
vlan-id
undo ntp-service source-interface
View
System view
Parameter
Vlan-interface vlan-id: Specifies an interface. The IP
address of the interface serves as the source IP address of sent NTP messages. The
vlan-id argument indicates the ID of the specified VLAN interface,
ranging from 1 to 4094.
Description
Use the ntp-service source-interface
command to specify a VLAN interface through which NTP messages are to be sent.
Use the undo ntp-service
source-interface command to remove the configuration.
If you do not want the IP addresses of the other
interfaces on the local device to be the destination addresses of response messages,
you can use this command to specify a specific interface to send all NTP packets.
In this way, the IP address of the interface is the source IP address of all
NTP messages sent by the local device.
Example
# Specify the source IP addresses of all sent
NTP messages as the IP address of Vla-interface1.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service source-interface Vlan-interface
1
1.1.15 ntp-service unicast-peer
Syntax
ntp-service unicast-peer
{ remote-ip | peer-name } [ authentication-keyid key-id
| priority | source-interface Vlan-interface vlan-id
| version number ]*
undo ntp-service
unicast-peer { remote-ip | peer-name }
View
System view
Parameter
remote-ip:
IP address of the NTP peer. This argument cannot be a broadcast address, a multicast
address, or the IP address of the local reference clock.
peer-name:
Peer host name, a string comprising 1 to 20 characters.
authentication-keyid key-id: Specifies the key ID used for
sending messages to the peer. The key-id argument ranges from 1 to
4294967295. You do not need to configure authentication-keyid key-id
if authentication is not required.
priority:
Specifies the peer identified by the remote-ip argument as the preferred
peer for synchronization.
source-interface Vlan-interface vlan-id: Specifies an interface whose IP
address serves as the source IP address of NTP message sent to the peer.
version number: Specifies the NTP version number. The version number ranges from 1
to 3 and defaults to 3.
Description
Use the ntp-service unicast-peer
command to configure an Ethernet switch to be an active NTP peer.
Use the undo ntp-service unicast-peer
command to remove the configuration.
By default, the local Ethernet switch is not
configured as an active NTP peer.
If you use remote-ip to specify a remote server as the peer
of the local Ethernet switch, the local switch operates in the active peer mode.
In this case, the local Ethernet switch and the remote server can be
synchronized to each other.
Example
# Configure the local peer to obtain time
information from the peer with the IP address 128.108.22.44 and also to provide
time information to the remote peer. Set the NTP version number to 3. The source
IP address of NTP messages is the IP address of Vlan- interface1.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service unicast-peer 128.108.22.44
version 3 source-interface Vlan-interface 1
Syntax
ntp-service unicast-server
{ remote-ip | server-name } [ authentication-keyid key-id
| priority | source-interface Vlan-interface vlan-id |
version number ]*
undo ntp-service
unicast-server { remote-ip | server-name
}
View
System view
Parameter
remote-ip:
IP address of an NTP server. This argument cannot be a broadcast address,
multicast group address, or IP address of a reference clock.
server-name:
NTP server name, a string comprising 1 to 20 characters.
authentication-keyid key-id: Specifies the key ID used for
sending messages to the NTP server. The key-id argument ranges from 1 to
4294967295. You do not need to configure authentication-keyid key-id
if authentication is not required.
priority: Specifies
the server identified by the remote-ip or the server-name argument
as the preferred server.
source-interface Vlan-interface vlan-id: Specifies an interface whose
IP address serves as the source IP address of NTP packets sent by the local
device to the server.
version
number: Specifies the NTP version number. The number
argument ranges from 1 to 3 and defaults to 3.
Description
Use the ntp-service unicast-server
command to configure an Ethernet switch to operate in the NTP client mode.
Use the undo ntp-service unicast-server
command to remove the configuration.
By default, no
Ethernet switch operates in the NTP client mode.
The remote server
specified by remote-ip serves as the NTP server and the local Ethernet
switch serves as the NTP client. The client can be synchronized to the server
while the server cannot be synchronized to the client.
Example
# Configure the local device to be
synchronized to the NTP server with the IP address 128.108.22.44, and set the version
number to 3.
<H3C> system-view
System View: return to User View with
Ctrl+Z.
[H3C] ntp-service unicast-server
128.108.22.44 version 3
