Avaya J169 Installing And Administering page 86

Administering your phone
Expired leases cause IP Deskphones to restart. Avaya recommends providing
enough leases so the IP address of a IP deskphones does not change if you briefly
take the phone offline.
Note:
The DHCP standard states that when a DHCP lease expires, the device must
immediately cease using the assigned IP address. However, if the network has
problems and the you centralize the DHCP server, or if the DHCP server has
problems, the deskphone does not receive responses to its request for a renewal
of the lease. In this case the deskphone is unusable until the server can respond.
Expired leases do not cause the phone to restart because you can renew expired
leases. However, if the new IP address is different than the previous, the phone
restarts. Ensure that after an IP address is assigned, the deskphone continues
using that address after the DHCP lease expires, until the system detects a
conflict with another device. With the system parameter DHCPSTD, an
administrator can specify that the telephone will do one of the following: a).
Comply with the DHCP standard by setting DHCPSTD to 1. b). Continue to use
the IP Address after the DHCP lease expires by setting DHCPSTD to 0. This
setting is the default. If you invoke the default after the DHCP lease expires, the
phone continues to broadcast DHCPREQUEST messages for the current IP
address. The deskphone sends an ARP Request for its own IP Address every 5
seconds until the phone receives a DHCPACK, a DHCPNAK, or an ARP Reply.
After receiving a DHCPNAK, or ARP Reply, the phone displays an error
message, sets the IP address to 0.0.0.0, and attempts to contact the DHCP
server again. Depending on the DHCP application you choose, be aware that the
application does not immediately recycle expired DHCP leases. An expired lease
might remain reserved for the original client for one day or more.
The following example shows the implication of having a reservation period: Take two
IP addresses, therefore two possible DHCP leases. Take three IP deskphones, two of
which are using the two available IP addresses. When the lease for the first two
deskphones expires, the third deskphone cannot get a lease until the reservation
period expires. Even if you remove the other two deskphones from the network, the
third deskphone remains without a lease until the reservation period expires.
- Option 52: Overload Option, if required. If the IP deskphones receives this option in
a message and interprets the sname and file fields in accordance with IETF RFC
2132, Section 9.3.
- Option 58: DHCP lease renew time. If the IP deskphones does not receive this
parameter, or if this value is greater than that for Option 51, the phone uses the
default value of T1 (renewal timer) according to IETF RFC 2131, Section 4.5.
- Option 59: DHCP lease rebind time. If the IP deskphones does not receive this
parameter, or if this value is greater than that for Option 51, the phone uses the
default value of T2 (rebinding timer) according to RFC 2131, Section 4.5
- Option 242: Site-Specific Option Number (SSON). You do not have to use Option
242. If you do not use this option, you must ensure that you administer the key
information, especially HTTPSRVR and MCIPADD appropriately elsewhere.
May 2018 Installing and Administering Avaya J169/J179 IP Phone H.323
Comments on this document? infodev@avaya.com
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