Hirschmann GREYHOUND GRS1020, Reference Manual

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Specifying the IP parameters
2.1 IP parameter basics
44
UM Config GRS
Release 8.0 09/2019
Example of applying the subnet mask to IP addresses for subnetwork assignment:
Example of how the netmask is used
In a large network it is possible that Gateways and routers separate the management agent from
its network management station. How does addressing work in such a case?
Figure 14: The management agent is separated from its network management station by a router
The network management station “Romeo” wants to send data to the management agent “Juliet”.
Romeo knows Juliet's IP address and also knows that the router “Lorenzo” knows the way to Juliet.
Romeo therefore puts his message in an envelope and writes Juliet's IP address as the destination
address; for the source address he writes his own IP address on the envelope.
Romeo then places this envelope in a second one with Lorenzo's MAC address as the destination
and his own MAC address as the source. This process is comparable to going from Layer 3 to
Layer 2 of the ISO/OSI base reference model.
Finally, Romeo puts the entire data packet into the mailbox which is comparable to going from
Layer 2 to Layer 1, that means to sending the data packet over the Ethernet.
129.218.65.17
Decimal notation
10000001.11011010.01000001.00010001
Binary notation
128 < 129 191 › Class B
Subnetwork 1
Network address
129.218.129.17
Decimal notation
10000001.11011010.10000001.00010001
Binary notation
128 < 129 191 › Class B
Subnetwork 2
Network address
Romeo
LAN 1
Lorenzo
LAN 2
Juliet