
	Home > Ask the Unified Communications Experts > IP Telephony Questions & Answers > DHCP lease renewal on IP phones

Ask The Unified Communications Expert: Questions & Answers

EMAIL THIS

DHCP lease renewal on IP phones

EXPERT RESPONSE FROM: Patrick Ferriter

		Pose a Question

		Other Unified Communications Categories

		Meet all Unified Communications Experts
		Become an Expert for this site

Digg This!

StumbleUpon

Del.icio.us

QUESTION POSED ON: 03 June 2005
As most IP Phones get IP addresses via DHCP from the service provider (I am thinking ITSP) - what happens to voice on a VoIP connection when the IP phone's DHCP lease expires? Does it drop the call and then reconnect? Or does it re-extend the lease time of the IP address? If it extends the lease time, is there a maximum time after which it must re-lease the IP address?

EXPERT RESPONSE
There are some IP phones that sit directly behind an integrated access device (IAD) such as a cable modem and act as a DHCP client on the WAN and a DHCP server on the LAN. The DHCP lease on the WAN interface will come from the local ISP (which also may be an ITSP). There are not many IP phones like this on the market, as the phone typically provides firewall and NAT functions when used in this mode.

One phone like this is the ZIP4x5 from Zultys. Most IP phones do not have this function built in and will likely get their DHCP IP address from a little router in the home office such as a Linksys or Netgear. In either case, the same question remains as to how IP phones behave when on a call and renewing the DHCP lease.

The answer is that this will depend on the IP phone manufacturer. Most phones (if lease renewal is successful) will have no interruption in the call. If lease renewal is not successful, the behavior again depends upon the phone manufacturer. One option is to keep the current call up and then indicate the failure to renew the DHCP address once the call clears and the other is to drop the call. I am not aware of any manufacturer that tries to artificially extend the lease from the phone side.

Digg This!

StumbleUpon

Del.icio.us

RELATED CONTENT

	IP Telephony
	Is VoIP just a business staple or is it primed for mainstream adoption?
	VoIP vendors focused on solving customer's networking issues.
	VoIP for the globe-trotting frequent traveler
	Is there a difference between VoIP and IP telephony?
	Highest acceptable latency to attempt a VoIP call over
	Communicate between 2 Sipuras in a private network
	Impact of VoIP E911
	VoIP in cell phone systems
	Calculate bandwidth for VoIP
	Where can I find reports on unbiased comparisons of the different IP phone systems?

IP Telephony

Is VoIP just a business staple or is it primed for mainstream adoption?

VoIP vendors focused on solving customer's networking issues.

VoIP for the globe-trotting frequent traveler

Is there a difference between VoIP and IP telephony?

Highest acceptable latency to attempt a VoIP call over

Communicate between 2 Sipuras in a private network

Impact of VoIP E911

VoIP in cell phone systems

Calculate bandwidth for VoIP

Where can I find reports on unbiased comparisons of the different IP phone systems?

RELATED RESOURCES

2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems

Search Bitpipe.com for the latest white papers and business webcasts

Whatis.com, the online computer dictionary

Search and Browse the Expert Answer Center
Search and browse more than 25,000 question and answer pairs from more than 250 TechTarget industry experts.

Browse our Expert Advice
Operating Systems IT Management Networking Database	Security Servers and Storage Applications and Development Career Center

SEARCH

TechTarget provides enterprise IT professionals with the information they need to perform their jobs - from developing strategy, to making cost-effective IT purchase decisions and managing their organizations' IT projects - with its network of technology-specific Web sites, events and magazines.


TechTarget Corporate Web Site \| Media Kits \| Reprints \| Site Map All Rights Reserved, Copyright 2008, TechTarget \| Read our Privacy Policy