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User Guide for Cisco Security Manager 4.4
OL-28826-01
Chapter 60 Router Device Administration
NTP Policy Page
Field Reference
Table 60-42 NTP Server Dialog Box
Element Description
IP Address The IP address of the NTP server. Enter an address or the name of a
network/host object, or click Select to select the object from a list or to
create a new one.
Source Interface The source address for all packets sent to this NTP server. This setting
might be necessary when the NTP server cannot respond to the address
from which the packet originated (for example, due to a firewall). The
source interface must have an IP address.
If you do not define a value in this field and there is no global setting,
the address of the outgoing interface is used.
Note This setting overrides the global setting you defined on the NTP
Policy Page, page 60-98.
Enter the name of an interface or interface role, or click Select to select
the object from a list or to create a new one.
Preferred When selected, this NTP server is preferred over other NTP servers of
similar accuracy. If this server is used for synchronization, the time
offset used to correct the local clock is calculated from this server only.
Note If a different NTP server is significantly more accurate than the
preferred server (for example, stratum 2 versus stratum 3), the
router synchronizes to the more accurate server.
When deselected, this NTP server is not given preference over other
NTP servers of similar accuracy. The time offset used to correct the
local clock is calculated by taking the combined offset of all NTP
servers.
We recommend that you configure an NTP server as preferred only
when multiple servers have the same stratum and you can rely on the
accuracy of the preferred server.
Authentication Key The MD5 key that is used to authenticate associations with the NTP
server.
• Key Number—The ID number of the authentication key. Enter the
key number or select a previously defined number from the list.
• Key Value—An arbitrary string of up to 32 characters that defines
the authentication key. Enter the string again in the Confirm field.
• Trusted—When selected, this key authenticates the identity of
systems attempting to synchronize with this server. When
deselected, this key is not used for authentication.
If you select a key number from the list and then change the key value,
you are warned that saving this change affects any other NTP servers
using the same authentication key.
Note To use authentication, you must enable it from the NTP Policy
Page, page 60-98.