Common Networking Protocols in LAN, WAN and Datacenter

Spanning Tree, Link Aggregation , VLAN and First Hop Redundancy protocols are used in Campus, Service Provider Access and Aggregation and in the Datacenter environment. There are definitely other protocols which are common across the Places in the Networks but in order to keep this article short and meaningful I choose these four.  

I will describe Spanning tree, link aggregation, 802.1q Vlan and First hop redundancy protocols at a high level since I will explained them in detail later in the separate articles. For the more advanced layer 2 protocol information check this article.  

Spanning Tree – IEEE 802.1d, 802.1w, 802.1s

Spanning tree is used to build a control path between the Ethernet switches in the campus , service provider and data center environment. It prevents data plane loops by creating a tree ! Loop preventation is very crirical for the Ethernet since there is no TTL value or any other loop mitigation mechanism encoded in the Ethernet header. Loop prevention is achieved by blocking the link which has a higher cost to the root switch in the topology.

802.1d is also known as original spanning tree or legacy spanning tree has been extended by Cisco and named as PVST+. PVST+ works in a similar way with 802.1d, only the link is blocked for each Vlans separately. Topology can be adjusted by placement of root switch. Thus PVST+ provides flexibility compare to 802.1d , since with 802.1d legacy spanning tree, only one tree can be created and all the Vlans are mapped to that tree. Redundancy can be provided as active/standby with 801.2 legacy spanning tree but with PVST+ which is Cisco’s implementation of 802.1d ; links can be used simultaneously by having Vlan based load balancing.

Even and Odd Vlan root switch placement at the distribution layer is very common deployment method and provides deterministic topology thus troubleshooting can be easier. But if the number of Vlans are high, configuration can be quite complex. Rapid Spanning Tree is the IEEE work which has several enhancements to original 802.1d and called 802.1w. Rapid Spanning Tree is used for fast convergence commonly and author recommends it strongly for the Campus Networks. MST which is 802.1s is the third implementation of spanning tree and use case is data center and service provider access networks which have thousands of Vlans and require large scale bridging support.

Down side of spanning tree is to block the links for any given Vlan and root switch placement for odd/even vlan is complex to manage. Alternative approach for the Campus Networks is Link Aggregation or Multi Chassis Link Aggregation which is the subject of next concept. There are other drawbacks of spanning tree such as suboptimal traffic flow, lack of multpathing and so on and can be avoided by using other protocols such as SPB, TRILL, Fabricpath. You can find more information about large scale bridging from here.  

Link Aggregation – IEEE 802.3ad

  To overcome to drawback of spanning tree which is the blocking links, link aggregation can be used between the switches. Link aggregation is used for both load sharing and redundancy. At least two links is placed in a bundle and load sharing and depends on vendor implementation 4, 8, 16, 32 links can be placed in a bundle. Link aggregation might be used between the access-aggregation/distribution layers and distribution to core layers depends on capacity requirements.

Link aggregation works between two switches and if it will be run between three or more switches then it is called as multi chassis link aggregation. Aggregation/distribution layer devices synchronize the state information through over the inter switch links. Over the inter switch link synchronization can be achieved with ICCP (Inter Chassis Communication protocol) or with vendor specific protocols. VSS and VPC are the two technologies which are known by the network engineers who have experience on Cisco switches use multi chassis link aggregation to bundle two physical chassis into one logical device.  

VLAN – Virtual Local Area Network / 802.1q

With adding another tag on the Ethernet frame, virtualization and segmentation can be achieved. Similar to VSAN technology of Cisco in the storage area network, IEEE 802.1q adds a 4 byte header to the Ethernet frame and addresses the segmentation and multi tenancy in the campus,service provider and the datacenter networks. VLAN concept is used to address either for broadcast/multicast or security concern. Broadcast, unknown unicast and multicast packets which also known as BUM traffic is flood everywhere in the network.

By separating the network with VLANs, BUM traffic is only flooded in that particular VLAN. What happens in Vegas stay in Vegas!. Since the NICs of PCs and servers has to process every broadcast packets , limiting these traffic by diving users into separate VLAN is very common practice and recommended by the Author. Another use case of VLAN is security. Inter VLAN traffic might be passed through the security devices such as Firewalls, IDS/IPS and unwanted communication or even zero day attacks can be prevented.  

First Hop Redundancy Protocols – HSRP, VRRP, GLBP

If the requirement is to use the same Vlan on the many access switches, then layer 2 access design is used at the campus network. Layer 2 access design will be explained later in the article. In the layer 2 access design , distribution layer switches is used as the default gateway for the end host. For high availability purpose using at least two distribution switches is the best practice. Question is which distribution layer switches will be the gateway of the hosts for the particular Vlan?.

There are three approaches for the first hop gateway redundancy. HSRP ( Hot standby router protocol ) , VRRP ( Virtual router redundancy protocol ) and GLBP ( Gateway load balancing protocol ) . HSRP is the Cisco propriety protocol and works as an active standby fashion. For a particular Vlan , only one of the switches will be active and the other switch will take the responsibility if the active device fails. VRRP is the IETF’s answer to the problem and works in a similar way with HSRP.

Common deployment method for HSRP and VRRP is to use one switch as default gateway for set of Vlans and the other switch for the remaining Vlans. Depends on the number of Vlans , this approach might be complex from the configuration point of view. GLBP is the Cisco propriety default gateway redundancy protocol as well. GLBP provides a redundancy for the hosts within the same Vlan. Two switches actively forward the traffic for the hosts in the same Vlan. If one switch fails only half of the hosts on that Vlan is affected. With HSRP and VRRP, if active switch fails , all the hosts on that Vlan is affected from the failure.

Created by
Orhan Ergun

Orhan Ergun, CCIE/CCDE Trainer, Author of Many Networking Books, Network Design Advisor, and Cisco Champion 2019/2020/2021

He created OrhanErgun.Net 10 years ago and has been serving the IT industry with his renowned and awarded training.

Wrote many books, mostly on Network Design, joined many IETF RFCs, gave Public talks at many Forums, and mentored thousands of his students.  

Today, with his carefully selected instructors, OrhanErgun.Net is providing IT courses to tens of thousands of IT engineers. 

View profile

Daniel Lardeux
Daniel Lardeux Senior Network Consultant at Post Telecom

I passed the CCDE Practical exam and Orhan’s CCDE course was very important contributor to my success. I attended the CCDE course of Orhan Ergun in July and it was exactly what I needed, Orhan is taking the pain to break down the different technologies.

Roy Lexmond
Roy Lexmond Senior Network Designer at Routz CCDE #20150017 & CCIE R&S; #26557

After I attended Orhan Ergun’s CCDE course I passed the CCDE practical exam.I really enjoyed the course a lot ...

Nicholas Russo
Nicholas Russo Network Consulting Engineer (CCDE/CCIEx2), Cisc

I signed up for Orhan’s CCDE training. This training is very technically detailed and the use-cases, quizzes, scenarios, and mind maps are all great resources in the overall training program. Orhan teaches his students to think like a network designer ...

Slide Heading
Slide Heading Network Systems Engineer at Conscia A/S CCIE #42544 (SP) & CCDE #20160015

Orhan is forcing you to take off the implementation hat that most of us have been wearing for many years, instead he is providing a new fancy design hat, which makes you see and deal with the issues presented ...

Kim Pedersen
Kim Pedersen CCIE in RS and SP (#29189) CCDE#20170021

I’ve used Orhan’s self-paced CCDE training material. If you are interested in knowing how all the technologies go together in a coherent design i can highly recommend it.I also enjoyed the Quizzes which helped pick out my weak spots in selecting ...

Laurent Metzger
Laurent Metzger 3xCCIE/CCDE Senior Network Architect

Hi Orhan. I passed the CCDE exam on February 22. I read everything that you put on your Self Paced CCDE Training course and it was very helpful in my success. Thank you very much.

Martin J. Duggan
Martin J. Duggan Network Architect at AT&T;, Ciscopress Author CCDE #20160006 & CCIE#7942

I attended Orhan’s April 201610 days CCDE Bootcamp. I am CCDE now !

You can tell Orhan has a great deal of experience, it really comes through when he presents his design case studies and the CCDE Practical scenarios.

Muhammad Abubakar
Muhammad Abubakar Lead Network Architect – CCDE #20160016 2xCCIE #26693 2xJNCIE VCIX

Your excellent CCDE materials and amazing Bootcamp helped me tremendously through my learning journey.Also thank you very much for being available whenever I have a design question or a complex design topics. I can’t compare your design skills ...

Jennifer Pai
Jennifer Pai Network/Security Engineer at KNET Technology

Thanks Orhan very much for this course. It helped strengthen my “Network design mind”.

Ruslan Silyayev
Ruslan Silyayev Solution Architect at R.I.S.K Company

Training by Orhan is not a CCDE preperation training only. It will be useful for engineers which are dealing with design. You want to pass CCDE exam or learn network design, then don’t look at anywhere else!

Sameer Meher
Sameer Meher Solutions Architect at 23 Wards/Japan

Orhan Ergun’s CCDE course was really very good. CCDE Level Intelligence was delivered very well and with very useful case studies and the scenarios, I am thankful to Orhan for all his help!

Ken Young
Ken Young Senior Technical Architect Province of Nova Scotia, 2xCCIE #41597 | CCDE #20170047

If anyone wants to understand network design and architecture, also pass CCDE exam , I recommend you to attend Orhan’s online courses! I am a CCDE now but learning is a journey, we will be together in your other courses too Orhan!

Matt Cross
Matt Cross Technical Architect at Heartland – CCDE #2019::7

Orhan did an excellent job of filling in the gaps of knowledge that I had that took me to the finish line of the practical exam CCDE. The community of people that Orhan facilitates are both engaging and supportive of the journey to CCDE. Orhan ...

Shiling Ding
Shiling Ding Sentinel Technologies – CCDE #2019::12

Just passed the CCDE Practical exam! I attended Orhan Ergun’s CCDE training program , used Orhan’s Instructor Led and Self-Paced CCDE training and Online CCDE Practical Scenarios during my CCDE journey. Orhan’s CCDE In Depth book is an excellent summary ...

Abelardo Basurto
Abelardo Basurto Solutions Architect at Cisco Systems – CCDE 2018::6

Hi everyone, I’ve just passed the CCDE Exam. My Number is CCDE 2018::6 I attended to Online CCDE Bootcamp of Orhan. I want to thank Orhan not only for the great book and bootcamp, but also for his commitment, availability and willingness to assist the ...

Hady Mohamed Abdellah
Hady Mohamed Abdellah Network Architect Hamad International Airport Qatar – CCDE 2018::1

Hi guys, I’m so happy that I passed the exam. I’ve already got my number CCDE 2018::1. Thanks to Orhan for being the best CCDE instructor in the world. I highly recomend Orhan’s CCDE Training and In-Depth-CCDE ...

Bryan Bartik
Bryan Bartik Sr. Systems Engineer at CompuNet – CCDE 20170059

Hi Orhan I passed CCDE Practical exam on November 2017 ! I really enjoyed your materials and quizzes and use cases. They were definitely helpful in my preparation. Thanks a lot !

Giedrius Trapkauskas
Giedrius Trapkauskas Network Solutions Architect at Liberty Global – CCDE 20180004

I attended Orhan’s CCDE Training in Istanbul and it was very helpful in my preparation. I passed the exam recently and I want to say Thank you Orhan! For those who want to pass the CCDE exam, definitely start with ...

Alaa Issa
Alaa Issa Sr.Solutions Architect – CCDE#20180033 3xCCIE ( Collab|DC|Security )#27146

I registered to Orhan’s training in Feb 2017. From that time, I attended Orhan’s training several times. The depth of knowledge which Orhan has is amazing, and how to present such consistent knowledge to the ...

Mazin Ahsan Design Lead Engineer | Solutions Engineer | CCDE License # 20160030 | CCIE Licence # 23892

I passed the CCDE Practical Lab exam on November 17,2016 from supplications of elders and dedication from my Sensei Mr. Orhan Ergun I took different CCDE bootcamps in the past. Orhan has the most depth and expertise ...

Jeff Patterson CCDE# 2018::11

Hi Orhan I wanted to pass along my appreciation for the outstanding training material. I used the online CCDE training provided by Orhan as well as the In-Depth-CCDE book and passed the exam in February 2018. Thank you Orhan!

Mehdi Sfar
Mehdi Sfar Network and Security Architect / CCDE #20210003 | CCIE R&S; #51583

I signed up for Orhan’s CCDE Self paced Course. This course, along with the CCDE In Depth book, helped me for my CCDE Practical as well as Written exams. It pushed me to ask the "WHY" questions and allowed ...

Related courses

CCIE Enterprise Infrastructure Training

117:12:56 Hours
287 Lectures


Cisco CCNP ENCOR 350 - 401 Training

41:36:12 Hours
137 Lectures


Cisco Datacenter Networking Fundamentals Training

15:22:21 Hours
57 Lectures