NoteWhen the DHCP Server feature is disabled and external DHCP servers are not used, static IPaddressing must also be enabled for all IP telephones.5.1.7 Network DevicesYou must evaluate the network devices that are used in the existing network to see if a VoIP network can beimplemented. Below are the points that should be evaluated.Are layer 2 or higher switches used?Use of repeater hubs can increase the network load, and therefore may result in degradation in speechquality.To ensure high speech quality, use only layer 2 or higher switches. Use of layer 2 or higher switches is alsostrongly recommended for connecting IP telephones.NoteNote that the port of the switching hub that connects to the mother board should be set to operate under"Auto Negotiation" mode.Does all equipment on the LAN support 1000BASE-T connection?To use the Gigabit Ethernet feature for the LAN, all equipment on the LAN must support 1000BASE-T. Formore information, consult your network administrator.Are Category 5 (CAT 5) or higher cables used for 10BASE-T/100BASE-TX?When connecting network devices, make sure to use CAT 5 or higher cables for 10BASE-T/100BASE-TXconnection. If other types of cables are used, communication may not be carried out normally.Are Enhanced Category 5 (CAT 5e) or higher cables used for 1000BASE-T?When connecting network devices, make sure to use CAT 5e or higher cables for 1000BASE-T. If othertypes of cables are used, communication may not be carried out normally.5.1.8 Network Time Protocol (NTP)The Control Box can be configured to contact an NTP server to receive and update its time settingautomatically.For a SIP phone to receive and update its time setting via the Control Box, the NTP server feature must beenabled. To enable this feature refer to "16.2.3 Network Service—[2-6] Server Feature—NTP" in the PCProgramming Manual.If the NTP server feature is enabled:• Case 1: An NTP server is specified in Web Maintenance Console.– The SIP phones use the specified IP address and contact the NTP server directly.• Case 2: An NTP server is not specified in Web Maintenance Console.– The SIP phones use the IP address of the Control Box as their NTP server.(The Control Box acts as an NTP server for the SIP phones.)To specify the IP address of the NTP server, refer to "10.1.2 Control Box Configuration—[2-1-2] System—Date & Time—SNTP / Daylight Saving" in the PC Programming Manual.If the NTP server feature is disabled, the SIP phones use their own time settings.5.1.7 Network Devices54 Installation Manual