Cisco Systems IPS4510K9 Configuring a Cisco Router to be an NTP Server

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Cisco Intrusion Prevention System Sensor CLI Configuration Guide for IPS 7.2
OL-29168-01
Chapter3 Setting Up the Sensor
Configuring Time
Configuring a Cisco Router to be an NTP Server
The sensor requires an authenticated connection with an NTP server if it is going to use the NTP server
as its time source. The sensor supports only the MD5 hash algorithm for key encryption. Use the
following procedure to activate a Cisco router to act as an NTP server and use its internal clock as the
time source.
Caution The sensor NTP capability is designed to be compatible with Cisco routers acting as NTP servers. The
sensor may work with other NTP servers, but is not tested or supported.
Note Remember the NTP server key ID and key values. You need them along with the NTP server IP address
when you configure the sensor to use the NTP server as its time source.
To set up a Cisco router to act as an NTP server, follow these steps:
Step 1 Log in to the router.
Step 2 Enter configuration mode.
router# configure terminal
Step 3 Create the key ID and key value. The key ID can be a number between 1 and 65535. The key value is
text (numeric or character). It is encrypted later.
router(config)# ntp authentication-key key_ID md5 key_value
Example
router(config)# ntp authentication-key 100 md5 attack
Note The sensor only supports MD5 keys.
Note Keys may already exist on the router. Use the show running configuration command to check
for other keys. You can use those values for the trusted key in Step 4.
Step 4 Designate the key you just created in Step 3 as the trusted key (or use an existing key). The trusted key
ID is the same number as the key ID in Step 3.
router(config)# ntp trusted-key key_ID
Example
router(config)# ntp trusted-key 100
Step 5 Specify the interface on the router with which the sensor will communicate.
router(config)# ntp source interface_name
Example
router(config)# ntp source FastEthernet 1/0