NTP Configuration
©2008 Allied Telesis Inc. All rights reserved.
Software Version 5.2.1
AlliedWare Plus
TM
Operating System Software Reference C613-50003-00 REV E
50.3
There is no provision in NTP for peer discovery, acquisition, or authentication. Data integrity is
provided by the IP and UDP checksums. No reachability, circuit-management, duplicate-
detection, or retransmission facilities are provided or necessary.
By its very nature clock synchronization requires long periods of time (hours or days) and
multiple comparisons in order to maintain accurate timekeeping. The more comparisons
performed, the greater the accuracy of the timekeeping.
NTP on the Switch
The implementation of NTP on the Switch is based on the following RFCs:
■
RFC 958, Network Time Protocol (NTP)
■
RFC 1305, Network Time Protocol (Version 3) Specification, Implementation and Analysis
■
RFC 1510, The Kerberos Network Authentication Service (V5)
Two modes of operation are supported: client and server. The switch is in client mode most of
the time where it polls the configured peer at least once every preconfigured minimum time
period.
The peer that the switch refers to must be a more accurate clock source than the switch itself
or another switch directly connected to a more accurate clock source. The switch operates as
a secondary time server. It cannot operate as a primary time server unless the primary clock
source is operating in server mode. A primary clock source usually operates in broadcast mode,
which is not supported by the switch’s implementation of NTP. There is no support for clock
selection or filtering. When the switch receives a valid reply from the peer, it synchronizes its
own internal clock according to the information from the reply.
If the switch receives a synchronization request from an NTP client, it temporarily changes to
server mode. It replies to the request with the current time from the switch’s internal clock
along with other information useful for synchronization. The switch’s internal clock is accurate
to }0.005 seconds.
Troubleshooting
Problem
The switch is not assigning the time to devices on the LAN.
Solutions
■
Check that the NTP peer’s IP address is entered correctly.
■
Check that the NTP peer can reach the switch, by pinging the switch from the NTP peer.
Problem
The switch’s clock does not synchronize with the NTP peer.
Solution
■
The switch’s clock can synchronize with the NTP peer only when its initial time is similar to
the NTP peer’s time (after setting the UTC offset). Manually set the switch’s time so that it
is approximately correct, and enable NTP again.
■
Check that the UTC offset is correct.
Problem
The switch’s time is incorrect, even though it assigns the correct time to devices on the LAN.
Solution
The UTC offset is probably incorrect, or needs to be adjusted for the beginning or end of
summer time.