Guralp Systems CMG-DCM build <10,000 User Manual
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Acquisition Modules and Platinum Firmware
Initial set-up
3.2.1.3 Address discovery – GCFPing
Scream's “GCFPing” feature sends a specially formatted broadcast packet to all
hosts on the local network. Any GCF servers that see this packet should
respond with a GCF acknowledgement packet (GCFACKN). Scream displays
the IP addresses associated with all acknowledgement packets that it receives.
To use this feature, add a new UDP server with an IP address of
255.255.255.255. Right-click the server and select GCFPING from the context
menu. A window will appear as shown below if the ping packet is
acknowledged. In the control pane (at the bottom right of the main window),
a GCFACKN line will be printed for every address that responded to the
GCFPING. In the example below, you can see responses from 192.168.42.135,
192.168.42.98 and 192.168.42.139. These are the addresses of all GCF servers
listening on port 1567 on the local network.
3.2.2 Link-local addresses
Many systems, when configured for DHCP, will generate a random address if
no DHCP server is present. This is known as a “link-local” or APIPA address.
For IPv4 networks, it will be in the range 196.254.0.0 to 196.254.255.254 (i.e.
on the 196.254.0.0/16 network). For IPv6 networks, it will be in the fe80::/10
network. The random, host-specific part of the address is derived from the
(unique) MAC address, so there are unlikely to be conflicts between addresses
of systems in networks with small or medium numbers of hosts.
This is useful when, for example, visiting a remote EAM: A laptop can be
plugged directly into the network port of the EAM (using a cross-over cable, if
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Issue E - February 2014