Chapter 10: Technical Reference

DNS RESOLUTION

If you want Domain Name System (DNS) resolution, you need to specify the IP address for a device to be the DNS resolver. You can also specify another IP address to designate a second device for a secondary DNS resolver. The DNS device maps human-readable addresses to IP addresses. A human-readable address is one such as maggie.copro.company.com that contains a host name and domain. The DNS resolver maps that name to the IP address that is a numeric (four octet) value such as 192.168.30.25.

In previous versions of code, the provisioning of more than one PPP over ATM session required the manual configuration of DNS server addresses on the host computers. Changing from one session to another session also required manual configuration. This is because different sessions required different DNS server addresses, and the modem did not have a way to handle the DNS server address on a session by session basis.

DNS Relay solves this problem. With DNS Relay, the DNS server addresses are configured on a per session basis and all the hosts on the LAN have their DNS server addresses configured to the same address, the LAN IP address of the modem. Therefore, multiple hosts in different sessions configured for DHCP can receive the modem’s LAN IP address as the DNS server address. When a host sends out a DNS message to the modem, the modem looks up the source IP address in the User Assignment Table to determine the host’s session and the DNS server for that session. The modem replaces the destination IP address of the frame with the DNS server address configured for that session and sends the frame on its way.

TFTP SERVER

Trivial File Transfer Protocol (TFTP) is the TCP/IP standard for file transfer. It provides the service with minimal capability and minimal overhead. TFTP uses UDP for connectionless delivery.

A TFTP Server is a device on the network which stores files that other IP devices can access for file transfer using the TFTP protocol. The Megabit Modem is one of these IP devices and uses theTFTP server to download updated software in binary format.

Typical TFTP servers are not dedicated only for file transfer. Frequently, Microsoft Windows desktops are used to store the binary files. To create a TFTP server, several shareware programs are available through the Internet. Once you have selected and installed the TFTP server software, configure it to share a directory containing the binary files. To configure the Megabit Modem to access the TFTP server, see Chapter 9 on page 77.

Megabit Modem 400F, 500L, 600F, and 700F User Manual

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