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DHCP Server Administration
Issue 5 April 2010 47
The 1600 Series IP Telephones do not support Regular Expression Matching, and therefore, do
not use wildcards. For more information, see Administering Options for the
1600 Series IP
Telephones on page 67.
In configurations where the upgrade script and application files are in the default directory on
the HTTP server, do not use the HTTPDIR=<path>.
You do not have to use Option 242. If you do not use this option, you must ensure that the key
information, especially HTTPSRVR and MCIPADD, is administered appropriately elsewhere.
Avaya recommends that you administer DHCP servers to deliver only the options specified in
this document. Administering additional, unexpected options might have unexpected results,
including causing the IP telephone to ignore the DHCP server.
The media server name and HTTP server name must each be no more than 32 characters in
length.
Examples of good DNS administration include:
- Option 6: “aaa.aaa.aaa.aaa”
- Option 15: “dnsexample.yourco.com,zzz.zzz.zzz.zzz”
- Option 242: “MCIPADD=xxxx.xxx.xxx.xxx”
Depending on the DHCP application you choose, be aware that the application most
likely does not immediately recycle expired DHCP leases. An expired lease might
remain reserved for the original client a day or more. For example, Windows NT
®
DHCP reserves expired leases for about one day. This reservation period protects a
lease for a short time. If the client and the DHCP server are in two different time
zones, the clocks of the computers are not in sync, or the client is not on the network
when the lease expires, there is time to correct the situation.
The following example shows the implication of having a reservation period: Assume
two IP addresses, therefore two possible DHCP leases. Assume three IP telephones,
two of which are using the two available IP addresses. When the lease for the first two
telephones expires, the third telephone cannot get a lease until the reservation period
expires. Even if the other two telephones are removed from the network, the third
telephone remains without a lease until the reservation period expires.