Cisco Nexus 3548 - Configuring NTP Access Restrictions

Configuring NTP Access Restrictions
You can control access to NTP services by using access groups. Specifically, you can specify the types of
requests that the device allows and the servers from which it accepts responses.
If you do not configure any access groups, NTP access is granted to all devices. If you configure any access
groups, NTP access is granted only to the remote device whose source IP address passes the access list criteria.
Procedure
PurposeCommand or Action
Enters global configuration mode.switch# configure terminal
Step 1
Creates or removes an access group to control NTP access and
applies a basic IP access list.
switch(config)# [no] ntp
access-group {peer | serve |
Step 2
serve-only | query-only}
access-list-name
The access group options are scanned in the following order, from
least restrictive to most restrictive. However, if NTP matches a deny
ACL rule in a configured peer, ACL processing stops and does not
continue to the next access group option.
•
The peer keyword enables the device to receive time requests
and NTP control queries and to synchronize itself to the servers
specified in the access list.
•
The serve keyword enables the device to receive time requests
and NTP control queries from the servers specified in the
access list but not to synchronize itself to the specified servers.
•
The serve-only keyword enables the device to receive only
time requests from servers specified in the access list.
•
The query-only keyword enables the device to receive only
NTP control queries from the servers specified in the access
list.
(Optional)
Displays the NTP access group configuration.
switch(config)# show ntp
access-groups
Step 3
(Optional)
Saves the change persistently through reboots and restarts by copying
the running configuration to the startup configuration.
switch(config)# copy
running-config
startup-config
Step 4
This example shows how to configure the device to allow it to synchronize to a peer from access group
“accesslist1”:
switch# config t
switch(config)# ntp access-group peer accesslist1
switch(config)# show ntp access-groups
Access List Type
-----------------------------
accesslist1 Peer
switch(config)# copy running-config startup-config
Cisco Nexus 3548 Switch NX-OS System Management Configuration Guide, Release 6.x
59
Configuring NTP
Configuring NTP Access Restrictions