DHCP Generic Setup
Set up of a DHCP server involves the following phases:
- Installing the DHCP server software according to vendor instructions.
- Configuring the DHCP server with the following information:
- IP addresses available for the 4600 Series IP Telephones.
- Lease duration (six weeks or greater is recommended). Expired leases will cause Avaya IP Telephones to reboot. It is highly desirable to provide enough leases so that an IP Telephone’s IP Address does not change if it is briefly taken off-line.
- The following DHCP options:
- Gateway (router) IP address(es) (Table 4-2 , item 1). If more than one address is listed, the total list may contain up to 127 total ASCII characters, with IP addresses separated by commas with no intervening spaces.
- Subnet mask (Table 4-2 , item 3).
- Option 6 (DNS server(s) address list). If more than one address is listed, the total list may contain up to 127 total ASCII characters, with IP addresses separated by commas with no intervening spaces. At least one address in Option 6 must be a valid, non-zero, dotted decimal address - otherwise, DNS will fail.
- Option 15 (DNS Domain Name). This string should contain the domain name to be used when DNS names in system parameters are resolved into IP addresses. This domain name is appended to the DNS name before the 4600 IP Telephone attempts to resolve the DNS address. Option 15 is necessary if you wish to use a DNS name for the TFTP server; otherwise, you may specify a DOMAIN as part of TFTP customization, as indicated in DNS Addressing.
- Option 66 (TFTP Server Name).
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NOTE:
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Microsoft DHCP servers support only dotted-decimal format for TFTP addresses, not symbolic names. Option 66 need not be used if the TFTP server is identified in the Site Specific Option string (Option 176). However, to simplify configuration, we recommend that you use Option 66. If you use both Option 66 and Option 176 to identify TFTP servers, the value(s) in Option 176 will override the value(s) in Option 66.
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- A 4600 Series IP Telephone-specific DHCP option specifying information such as TFTP server and Avaya Media Server Gatekeeper IP addresses. Use the site-specific option (SSON) at #176. The value for this option should be set to either of the following strings:
MCIPADD=xxx.xxx.xxx.xxx,MCPORT=yyyy,TFTPDIR=<path>,TFTPSRVR=
zzz.zzz.zzz.zzz
OR
MCIPADD={list of DNS names},MCPORT=yyyy,TFTPDIR=<path>,TFTPSRVR=
{list of DNS names}
Where xxx.xxx.xxx.xxx is one or more IP addresses for Avaya Media Server Gatekeepers, yyyy is the Avaya Media Server Gatekeeper port (1719), zzz.zzz.zzz.zzz is one or more IP addresses for TFTP servers, and <path> is the location of the upgrade script and application files on the TFTP server as entered in Table 4-2 , items: 4, 5, 2, and 7, respectively. Each list may contain up to 127 total ASCII characters, with IP addresses separated by commas with no intervening spaces, and with quotes on either end (see the example in the NOTES on page 4-9). If you use DNS, note that the system value DOMAIN will be appended to the IP addresses you specify. If DOMAIN is null, the DNS names must be fully qualified.
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NOTE:
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The TFTPDIR value should be listed before the TFTPSRVR, if the latter is specified in the SSON.
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The 4600 Series IP Telephones do not support Regular Expression Matching, and therefore, do not use wildcards. See Administering Options for the 4600 Series IP Telephones.
In configurations where the upgrade script and application files are in the default directory, the TFTPDIR=<path> should not be used.
You do not have to use Option 176, but if you do not use it, you must ensure the key information (TFTPSRVR, MCIPADD, and MCPORT, especially) is administered appropriately elsewhere. For example, if the DNS server is specified in Option 6, and the Domain Name is specified in Option 15, you can use the configured names “AvayaTFTPServer” and “AvayaCallServer” for TFTPSRVR and MCIPADD, respectively. Upgrading from IP Telephone Releases prior to R1.60 requires Option 176 to be administered with, at a minimum, MCIPADD.
DHCP servers should be administered to deliver only the options specified in this document. Administering additional, unexpected options may have unexpected consequences, including possibly causing the IP Telephone to ignore the DHCP server.
The Media Server Name, TFTP Server Name, and SMTP Server Name must each be no more than 32 characters in length.
NOTE:
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- 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.
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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.
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. |
The remainder of this section describes some common DHCP servers.
