Section 2 - Functional Design; Network Concepts And Considerations; Mtu Throughout The Network; Dhcp Use - Harris CM-30 Installation & Operation Manual

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Section 2 – Functional Design
This section describes the intent of IP multiplexing and day-to-day operations of the NetXpress LX
system and the CM-30 IP interface module. The section also describes how to use the IP multiplexer
and interface module to configure real-time payload transport of audio and data over existing IP
networks.
Packet-based media transport with the NetXpress LX system or the CM-30 module provides
● Transport of audio, voice, data, and video.
● Flexibility when integrating to business applications, systems, and networks.
● Network monitoring.
● Error mitigation.
● Transition and migration from legacy systems with reuse of modules and components.

2.1 Network Concepts and Considerations

When looking at the NetXpress LX system (or the CM-30 module) and packet-switched services as a
whole, consider these network-related concepts:
●

MTU throughout the network

●

DHCP use

●

Routing table construction

● WAN port auto-negotiation
● ICMP support
● Redundant WAN link configuration
● IGMP multicast
2.1.1 MTU throughout the Network
Prior to configuring a stream, you need to know end-to-end MTU (Maximum Transmission Unit)
between stream endpoints, which you can measure using an external server or router and running the
"Path MTU" tool. The stream payload must be smaller than the path MTU, otherwise fragmentation
occurs, the stream does not come up, and the NetXpress LX system does not support re-assembly.
2.1.2 DHCP Use
Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a DHCP server to
automatically assign an IP address to an individual computer's IP network interface. DHCP dynamically
assigns a number from a defined range of numbers configured for a given network.
The NetXpress LX system supports dynamic address assignment for its LAN interface using DHCP. On
the WAN interface, only static IP address assignment is supported. You can elect to enable the DHCP
option for the management interface from the Networking Ethernet Interfaces Web page (Section
4.3.4 – Configure the Network). If DHCP is enabled and the system fails to successfully retrieve an IP
address, it defaults to the factory default address – 192.168.1.1.
2.1.3 Routing Table Construction
The behavior of the NetXpress LX system within the customer's network is that of an IP host. As such,
the NetXpress LX routing table is used solely to route internally generated packets. For streams that
are unicast, the determination of the next-hop gateway to reach the remote NetXpress LX shelf is
done by examining the system routing table.
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