
Customizing NTP Services
304234-A Rev 00
7-13
Configuring NTP Access Control
The access control feature allows you to selectively restrict NTP clients from
accepting NTP timestamps from specific remote time servers on the network by
filtering these timestamps based on the source IP address or an IP subnet address.
This is similar to an inbound filter that drops NTP packets based on source IP
address and IP subnet mask.
Configuring NTP access control for a time server involves:
• Specifying the IP address of the remote time server
• Specifying a filter type
• Specifying an IP subnet mask
Specifying the IP Address of the Time Server
When you specify the IP address of the remote time server whose access to the
local NTP client you want to restrict, NTP adds the IP address of the time server to
an access control list, which the local NTP client uses when querying remote time
servers for time information. Use the access control option when operating in
broadcast client and multicast client mode.
To specify the IP address of the remote time server whose access to the local NTP
client you want to restrict, complete the tasks in the following table.
Site Manager Procedure
You do this System responds
1. In the Configuration Manager window,
select
Protocols
.
The Protocols menu opens.
2. Choose
Global Protocols
. The Global Protocols menu opens.
3. Choose
NTP
. The NTP menu opens.
4. Choose
Access
. The NTP Access Configuration List
window opens.
5. Click on
Add
. The NTP Access Configuration window
opens.
(continued)
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