Managing the System Time and Date
Creating an Access Group and Assigning a Basic IP Access List
Beginning in privileged EXEC mode, follow these steps to control access to NTP services by using
access lists:
Command
Step 1
configure terminal
Step 2
ntp access-group {query-only |
serve-only | serve | peer}
access-list-number
Step 3
access-list access-list-number permit
source [source-wildcard]
Step 4
end
Step 5
show running-config
Step 6
copy running-config startup-config
The access group keywords are scanned in this order, from least restrictive to most restrictive:
1.
2.
3.
4.
Catalyst 2950 Desktop Switch Software Configuration Guide
7-40
Purpose
Enter global configuration mode.
Create an access group, and apply a basic IP access list.
The keywords have these meanings:
For access-list-number, enter a standard IP access list number from 1
to 99.
Create the access list.
Note
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
peer—Allows time requests and NTP control queries and allows the switch to synchronize itself to
a device whose address passes the access list criteria.
serve—Allows time requests and NTP control queries, but does not allow the switch to synchronize
itself to a device whose address passes the access list criteria.
serve-only—Allows only time requests from a device whose address passes the access list criteria.
query-only—Allows only NTP control queries from a device whose address passes the access list
criteria.
query-only—Allows only NTP control queries.
•
•
serve-only—Allows only time requests.
•
serve—Allows time requests and NTP control queries, but does not
allow the switch to synchronize to the remote device.
•
peer—Allows time requests and NTP control queries and allows the
switch to synchronize to the remote device.
•
For access-list-number, enter the number specified in Step 2.
•
Enter the permit keyword to permit access if the conditions are
matched.
For source, enter the IP address of the device that is permitted access
•
to the switch.
(Optional) For source-wildcard, enter the wildcard bits to be applied
•
to the source.
When creating an access list, remember that, by default, the end
of the access list contains an implicit deny statement for
everything if it did not find a match before reaching the end.
Chapter 7
Administering the Switch
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