H.323 Telephone Installation
Page 85
15-601046 Issue 17e (Wednesday, November 14, 2012)
IP Office
Alternate DHCP Server Setup:
6.1 Alternate Options
In this document, all IP phone information is issued through the Scope and the Option 176 settings. Depending on the
DHCP server, other options may have to be used within the scope.
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Option 1 - Subnet mask
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Option 3 - Gateway IP Address
If using more than one address, the total list can contain up to 255 total ASCII characters. You must separate IP
addresses with commas with no intervening spaces.
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Option 6 - DNS server(s) Address
If using more than one address, the total list can contain up to 127 total ASCII characters. You must separate IP
addresses with commas with no intervening spaces. At least one address in Option 6 must be a valid, non-zero,
dotted decimal address.
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Option 15 - DNS Domain Name
This string contains 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 IP telephone attempts to resolve the DNS
address. Option 15 is necessary if you want to use a DNS name for the HTTP server.
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Option 51 - DHCP Lease Time
If this option is not received, the DHCP offer is not accepted. Avaya recommends a lease time of six (6) weeks or
greater. If this option has a value of FFFFFFFF hex, the IP address lease is assumed to be infinite as per RFC 2131,
Section 3.3, so that renewal and rebinding procedures are not necessary even if Options 58 and 59 are received.
Expired leases cause Avaya IP Telephones to reboot.
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Avaya recommends providing enough leases so that an IP address for an IP telephone does not change if it is
briefly taken offline.
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DHCP standard states that when a DHCP lease expires, the device should immediately cease using its assigned
IP address. If the network has problems and the only DHCP server is centralized, the server is not accessible
to the given telephone. In this case the telephone is not usable until the server can be reached.
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Avaya recommends, once assigned an IP address, the telephone continues using that address after the DHCP
lease expires, until a conflict with another device is detected. The 1600 Series IP Telephone customizable
parameter DHCPSTD allows an administrator to specify that the telephone either:
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comply with the DHCP standard by setting DHCPSTD to 1
or
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continue to use its IP address after the DHCP lease expires by setting DHCPSTD to 0. This is the default.
If used, after the DHCP lease expires, the telephone sends an ARP Request for its own IP address every
five (5) seconds. The request continues either forever, or until the telephone receives an ARP Reply. After
receiving an ARP Reply, the telephone displays an error message, sets its IP address to 0.0.0.0, and
attempts to contact the DHCP server again.
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Option 52 - Overload Option
If this option is received in a message, the telephone interprets the name and file fields in accordance with IETF
RFC 2132, Section 9.3, listed in Appendix B: Related Documentation.
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Option 53 - DHCP Message Type
Value is 1 (DHCPDISCOVER) or 3 (DHCPREQUEST).
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Option 55 - Parameter Request List
Acceptable values are: 1 (subnet mask), 3 (router IP address[es]), 6 (domain name server IP address[es]), 15
(domain name), NVSSON (site-specific option number)
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Option 57 - Maximum DHCP Message Size
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Option 58 - DHCP Lease Renew Time
If not received or if this value is greater than that for Option 51, the default value of T1 (renewal timer) is used as
per IETF RFC 2131, Section 4.5.
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Option 59 - DHCP Lease Rebind Time
If not received or if this value is greater than that for Option 51, the default value of T2 (rebinding timer) is used
as per IETF RFC 2131, Section 4.5
Note: On H.323 IP phones, any Option 66 settings will be overridden by any TFTP entry in Option 176. Using Option
66 as part of the Scope is useful if alternate Gatekeeper addresses are required in the Option 176 settings whilst
keeping within the 127 character limit.
