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Server Administration
DHCP
4-9
The 4600 Series IP Telephone sets the indicated system values to the values of the indicated
fields of the DHCPACK message as indicated in Table 4-3
below.
The remainder of this section describes some common DHCP servers.
Windows NT
®
4.0 DHCP Server 4
This section contains details on how to verify and configure the DHCP server included in the
Windows NT
®
4.0 server operating system.
Use Verifying the Installation of the DHCP Server
below to verify whether the DHCP server is
installed. If it is not, install the DHCP server. If it is installed, go to the section Initial Configuration
,
on page 4-10 and the following section.
Examples of good DNS administration include the following:
- Option 6: “aaa.aaa.aaa.aaa”
- Option 15: “dnsexample.yourco.com”
- Option 66: “tftpserver.yourco.com,zzz.zzz.zzz.zzz”
- Option 176: “MCIPADD=xxxx.xxx.xxx.xxx”
Depending on the DHCP application you choose, you should be aware of the fact that
the application most likely will not immediately recycle expired DHCP leases. An
expired lease may remain reserved for the original client for a day or more (for
example, Windows NT
®
DHCP reserves expired leases for about one day). The intent
of this reservation period is to protect a client’s lease in case the client and the DHCP
server are in two different time zones, the computers’ clocks are not in synch, or the
client is not on the network when the lease expires.
The implication of this fact may be seen in the following example: Assume 2 IP
addresses (hence two possible DHCP leases) and three IP telephones, two of which
are using the two available IP addresses. When the lease expires for the first two
telephones, the third will not be able to get a lease (even if the other two telephones
have been removed from the network) until the reservation period expires.
Table 4-3. DHCPACK Setting of System Values
System Value Set to
IPADD The yiaddr field.
NETMASK Option #1 (if received).
GIPADD The first four octets of option #3 (if received).
TFTPSRVR The first four octets of the siaddr field.