Cisco ASA 5505 - Manual (Page 339)

10-5
Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter 10 Configuring Basic Settings
Setting the Date and Time
Step 2 ntp trusted-key key_id
Example:
hostname(config)# ntp
trusted-key 1
Specifies an authentication key ID to be a trusted key, which is required for
authentication with an NTP server.
The key_id argument is a value between 1 and 4294967295. You can enter
multiple trusted keys for use with multiple servers.
Step 3 ntp authentication-key key_id
md5 key
Example:
hostname(config)# ntp
authentication-key 1 md5
aNiceKey
Sets a key to authenticate with an NTP server.
The key_id argument is the ID you set in Step 2 using the ntp trusted-key
command, and the key argument is a string up to 32 characters long.
Step 4 ntp server ip_address [key
key_id] [source interface_name]
[prefer]
Example:
hostname(config)# ntp server
10.1.1.1 key 1 prefer
Identifies an NTP server.
The key_id argument is the ID you set in Step 2 using the ntp trusted-key
command.
The source interface_name keyword-argument pair identifies the outgoing
interface for NTP packets if you do not want to use the default interface in
the routing table. Because the system does not include any interfaces in
multiple context mode, specify an interface name defined in the admin
context.
The prefer keyword sets this NTP server as the preferred server if multiple
servers have similar accuracy. NTP uses an algorithm to determine which
server is the most accurate and synchronizes to that one. If servers are of
similar accuracy, then the prefer keyword specifies which of those servers to
use. However, if a server is significantly more accurate than the preferred
one, the ASA uses the more accurate one. For example, the ASA uses a
server of stratum 2 over a server of stratum 3 that is preferred.
You can identify multiple servers; the ASA uses the most accurate server.
Note In multiple context mode, set the time in the system configuration
only.