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8030HEPTA/GPS GPS - NTP Time Server with 2x 10/100/1000 MBit LAN Interface - V04.00
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hopf
Elektronik GmbH
Nottebohmstr. 41
• D-58511 Lüdenscheid • Tel.: +49 (0)2351 9386-86 • Fax: +49 (0)2351 9386-93 • Internet: http://www.hopf.com • E-Mail: [email protected]
8.3.3.4.4 Broadcast / Broadcast Address
This section is used to configure the Time Server 8030HEPTA/GPS as a broadcast or mul-
ticast server.
The broadcast mode in NTPv3 and NTPv4 is limited to clients on the same sub-network and
Ethernets which support broadcast technology.
This technology does not generally extend beyond the first hop (network node - such as router
or gateway).
The broadcast mode is provided for configurations which are designed to facilitate one or more
servers and as many clients as possible in a sub-network. The server continuously generates
broadcast messages at defined intervals, corresponding to 16 seconds (minpoll 4) for Time
Server 8030HEPTA/GPS. Care should be taken to ensure that the correct broadcast address
is used for the sub-network, usually xxx.xxx.xxx.255 (e.g. 192.168.1.255). If the broadcast
address is not known, this can be requested from the network administrator.
This section can also be used to configure the Time Server 8030HEPTA/GPS as a multicast
server. The configuration of a multicast server is similar to that of a broadcast server. However,
a multicast group address (class D) is used instead of the broadcast address.
An explanation of multicast technology goes beyond the scope of this document.
In principle, a host or router sends a message to an IPv4 multicast group address and expects
all hosts and routers to receive this message. In doing so, there is no limit to the number of
senders and receivers and a sender may also be a receiver and vice-versa. The IANA has
assigned the multicast group address IPv4 224.0.1.1 to the NTP, however this should only be
used if the multicast range can be safely limited in order to protect neighbouring networks. As
a basic principle, administratively manageable IPv4 group addresses should be used as de-
scribed in RFC-2365 or GLOP group addresses as described in RFC-2770.
8.3.3.4.5 Broadcast / Authentication / Key ID
Broadcast packets can be protected by authentication for security reasons.
If a security method is selected here, this must be configured
additionally
in the security set-
tings of the NTP tab. A key must be defined if the Symmetric Key is selected.
8.3.3.4.6 Additional NTP SERVERS
Adding further NTP servers provides the opportunity to implement a security system for the
time service. However, this affects the accuracy and stability of the Time Server
8030HEPTA/GPS.
Detailed information on this subject can be found in the NTP documentation
(
