Cisco 2950G 24 Software Configuration Guide - Page 194
Configuring the Source IP Address for NTP Packets, Disabling NTP Services on a Specific Interface
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Managing the System Time and Date Chapter 7 Administering the Switch If the source IP address matches the access lists for more than one access type, the first type is granted. If no access groups are specified, all access types are granted to all devices. If any access groups are specified, only the specified access types are granted. To remove access control to the switch NTP services, use the no ntp access-group {query-only | serve-only | serve | peer} global configuration command. This example shows how to configure the switch to allow itself to synchronize to a peer from access list 99. However, the switch restricts access to allow only time requests from access list 42: Switch# configure terminal Switch(config)# ntp access-group peer 99 Switch(config)# ntp access-group serve-only 42 Switch(config)# access-list 99 permit 172.20.130.5 Switch(config)# access list 42 permit 172.20.130.6 Disabling NTP Services on a Specific Interface NTP services are enabled on all interfaces by default. Beginning in privileged EXEC mode, follow these steps to disable NTP packets from being received on an interface: Step 1 Step 2 Step 3 Command configure terminal interface interface-id ntp disable Step 4 Step 5 Step 6 end show running-config copy running-config startup-config Purpose Enter global configuration mode. Enter interface configuration mode, and specify the interface to disable. Disable NTP packets from being received on the interface. By default, all interfaces receive NTP packets. Return to privileged EXEC mode. Verify your entries. (Optional) Save your entries in the configuration file. To re-enable receipt of NTP packets on an interface, use the no ntp disable interface configuration command. Configuring the Source IP Address for NTP Packets When the switch sends an NTP packet, the source IP address is normally set to the address of the interface through which the NTP packet is sent. Use the ntp source global configuration command when you want to use a particular source IP address for all NTP packets. The address is taken from the specified interface. This command is useful if the address on an interface cannot be used as the destination for reply packets. 7-42 Catalyst 2950 Desktop Switch Software Configuration Guide 78-14982-01
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