SHARE



ABOUT THE AUTHOR


Matt Brunk
Matt Brunk has worked in past roles as director of IT for a multisite health care firm; president of Telecomworx,...
Read Full Bio >>
SHARE



Matt Brunk | October 12, 2012 |

 
   

Inside the LAN: DHCP

Inside the LAN: DHCP DHCP continues to play an important role, but ensuring that your audience receives the intended IP address still requires a little more effort in a converged network.

DHCP continues to play an important role, but ensuring that your audience receives the intended IP address still requires a little more effort in a converged network.

The LAN still presents challenges, and managing onsite components is key for uptime. Recently, we engaged a beta project involving a telephony system on a campus that called for strategies to address growth while providing high availability.

We've learned from prior campus deployments (through the test of time) that using the local server or firewall for DHCP isn't always the best choice for handing out IP addresses to IP phones. In this particular deployment we decided early on to activate the phone system's onboard DHCP server. The reasoning is, it saves on IP addresses and isolates the function to the PBX and voice VLAN along with the broadcast, date/time, keep-alives and paging traffic.

Remember, the IP telephones connect to switch ports; these ports should be restricted to voice VLAN2 and set in the TRUNK mode in our example. The computers connect to the phones' secondary port that is set as VLAN1 (Data) also known as "Native VLAN1." For computers or desktops that connect directly to switch ports: these ports are set up as VLAN1 (Data) and (default), and can be set in the TRUNK mode and then allowed access to VLAN2 so the computers' UC clients can function when using the PBX as the UC server. Connecting the computer to either the phone (as noted above) or directly to the switch port tagged as VLAN1 will yield an IP address from the appropriate source, i.e., not the phone system.

In our situation, some old IP phones with old firmware made it onsite. The older firmware doesn't support native VLAN, and while we pointed the phone to the PBX IP address in a different subnet, it defaulted to native VLAN1, obtained an IP address and still worked. Why? The switch port the phone was connected to allow access to VLAN1 and VLAN2. DHCP in VLAN1 (Data) prevailed and that's what we didn't want.

After your initial phone discovery process, it's a good idea to view the phones and their IP addresses to ensure that they are on the proper subnet. While we set up a staging area in a conference room and used the same switch port to discover phones, the few small details--old firmware in some phones along with access to native VLAN1--created more unnecessary work. The local IT person had to remove the phones identifiable by MAC address from the DHCP pool and we simply rebooted the PBX to flush out the DHCP reservations.

WiFi creates new demand in schools. Students have one, two and sometimes three devices: an iPod, tablet, cell/smart phone and/or laptop. Using multiple SSIDs could relieve DHCP pools and isolate and prioritize traffic. For example:

SSID: GREAT SCHOOL
Use: School staff

SSID: STUDENTS
Use: Student devices for learning

SSID: GUEST
Use: Non-learning, personal use

Each SSID is associated with a VLAN, and the traffic from each VLAN can be prioritized. Then, each SSID is also associated with a DHCP pool. In my simplistic example there are unanswered questions. Depending upon the number of endpoints and available (budgeted) bandwidth, you can come up with different answers and whether or not the customer (school/business) will entertain student/employee personal use of WiFi. Have an acceptable use policy addressing the traffic assigned to higher or lower priorities upfront.

Microsoft offers three alternatives in, "Increasing the number of IP addresses on a subnet in DHCP Server"--scope extension, resubnetting and superscoping. We isolated the GUEST WiFi and let the Adtran IAD act as a DHCP server. Using simple firewall policies, the GUEST users are completely restricted to Internet access. DHCP continues to play an important role, but ensuring that your targeted audience receives the intended IP address still requires a little more effort in a converged network.





COMMENTS



Enterprise Connect Orlando 2018
March 12-15 | Orlando, FL

Connect with the Entire Enterprise Communications & Collaboration Ecosystem


Stay Up-to-Date: Hear industry visionaries in Keynotes and General Sessions delivering the latest insight on UC, mobility, collaboration and cloud

Grow Your Network: Connect with the largest gathering of enterprise IT and business leaders and influencers

Learn From Industry Leaders: Attend a full range of Conference Sessions, Free Programs and Special Events

Evaluate All Your Options: Engage with 190+ of the leading equipment, software and service providers

Have Fun! Mingle with sponsors, exhibitors, attendees, guest speakers and industry players during evening receptions

Register now with code NOJITTEREB to save $200 Off Advance Rates or get a FREE Expo Pass!

November 1, 2017

Your customers (internal and external) demand that you offer them the ability to connect by any means. With the adoption of cloud communications tools you now have access to an expanded portfolio o

October 18, 2017

Microsofts recent Ignite event had some critically important announcements for enterprise communications. Namely, Microsofts new Team Collaboration offering, Teams, will be its primary communicatio

September 20, 2017

Customer experience can make or break your business. But how do you achieve outstanding customer service when you're dealing with outdated organizational structure, lagging technology, dated proces

September 22, 2017
In this podcast, we explore the future of work with Robert Brown, AVP of the Cognizant Center for the Future of Work, who helps us answer the question, "What do we do when machines do everything?"
September 8, 2017
Greg Collins, a technology analyst and strategist with Exact Ventures, delivers a status report on 5G implementation plans and tells enterprises why they shouldn't wait to move ahead on potential use ....
August 25, 2017
Find out what business considerations are driving the SIP trunking market today, and learn a bit about how satisfied enterprises are with their providers. We talk with John Malone, president of The Ea....
August 16, 2017
World Vision U.S. is finding lots of goodness in RingCentral's cloud communications service, but as Randy Boyd, infrastructure architect at the global humanitarian nonprofit, tells us, he and his team....
August 11, 2017
Alicia Gee, director of unified communications at Sutter Physician Services, oversees the technical team supporting a 1,000-agent contact center running on Genesys PureConnect. She catches us up on th....
August 4, 2017
Andrew Prokop, communications evangelist with Arrow Systems Integration, has lately been working on integrating enterprise communications into Internet of Things ecosystems. He shares examples and off....
July 27, 2017
Industry watcher Elka Popova, a Frost & Sullivan program director, shares her perspective on this acquisition, discussing Mitel's market positioning, why the move makes sense, and more.
July 14, 2017
Lantre Barr, founder and CEO of Blacc Spot Media, urges any enterprise that's been on the fence about integrating real-time communications into business workflows to jump off and get started. Tune and....
June 28, 2017
Communications expert Tsahi Levent-Levi, author of the popular BlogGeek.me blog, keeps a running tally and comprehensive overview of communications platform-as-a-service offerings in his "Choosing a W....
June 9, 2017
If you think telecom expense management applies to nothing more than business phone lines, think again. Hyoun Park, founder and principal investigator with technology advisory Amalgam Insights, tells ....
June 2, 2017
Enterprises strategizing on mobility today, including for internal collaboration, don't have the luxury of learning as they go. Tony Rizzo, enterprise mobility specialist with Blue Hill Research, expl....
May 24, 2017
Mark Winther, head of IDC's global telecom consulting practice, gives us his take on how CPaaS providers evolve beyond the basic building blocks and address maturing enterprise needs.
May 18, 2017
Diane Myers, senior research director at IHS Markit, walks us through her 2017 UC-as-a-service report... and shares what might be to come in 2018.
April 28, 2017
Change isn't easy, but it is necessary. Tune in for advice and perspective from Zeus Kerravala, co-author of a "Digital Transformation for Dummies" special edition.
April 20, 2017
Robin Gareiss, president of Nemertes Research, shares insight gleaned from the firm's 12th annual UCC Total Cost of Operations study.
March 23, 2017
Tim Banting, of Current Analysis, gives us a peek into what the next three years will bring in advance of his Enterprise Connect session exploring the question: Will there be a new model for enterpris....
March 15, 2017
Andrew Prokop, communications evangelist with Arrow Systems Integration, discusses the evolving role of the all-important session border controller.
March 9, 2017
Organizer Alan Quayle gives us the lowdown on programmable communications and all you need to know about participating in this pre-Enterprise Connect hackathon.
March 3, 2017
From protecting against new vulnerabilities to keeping security assessments up to date, security consultant Mark Collier shares tips on how best to protect your UC systems.
February 24, 2017
UC analyst Blair Pleasant sorts through the myriad cloud architectural models underlying UCaaS and CCaaS offerings, and explains why knowing the differences matter.
February 17, 2017
From the most basics of basics to the hidden gotchas, UC consultant Melissa Swartz helps demystify the complex world of SIP trunking.
February 7, 2017
UC&C consultant Kevin Kieller, a partner at enableUC, shares pointers for making the right architectural choices for your Skype for Business deployment.
February 1, 2017
Elka Popova, a Frost & Sullivan program director, shares a status report on the UCaaS market today and offers her perspective on what large enterprises need before committing to UC in the cloud.
January 26, 2017
Andrew Davis, co-founder of Wainhouse Research and chair of the Video track at Enterprise Connect 2017, sorts through the myriad cloud video service options and shares how to tell if your choice is en....
January 23, 2017
Sheila McGee-Smith, Contact Center/Customer Experience track chair for Enterprise Connect 2017, tells us what we need to know about the role cloud software is playing in contact centers today.