# Introduction to Virtual Extensible LAN (VXLAN)
**URL:** https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744
**Category:** Lessons Discussion
**Created:** [February 6, 2020, 12:19pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744 "2020-02-06T12:19:00Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [February 6, 2020, 12:19pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/1 "2020-02-06T12:19:00Z")
This topic is to discuss the following lesson:
> **[Introduction to Virtual Extensible LAN (VXLAN)](https://networklessons.com/cisco/ccnp-encor-350-401/introduction-to-virtual-extensible-lan-vxlan)**
>
> Virtual Extensible LAN (VXLAN) lets you tunnel layer 2 traffic over a layer 3 network without the disadvantages of traditional layer 2 networks.
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### Author:  [@davide.concio](https://forum.networklessons.com/u/davide.concio)
#### Post date: [February 6, 2020, 4:02pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/2 "2020-02-06T16:02:24Z")
Hi Rene, this is a very good lesson on VXLAN, straight to the point and well written.
I’m particularly passionate to this topic because I worked on a VXLAN EVPN Fabric the last year and love this technology.
If I had done a lesson like this when I started It would have been easier to learn the topic…
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### Author:  [@bikram.na](https://forum.networklessons.com/u/bikram.na)
#### Post date: [April 17, 2020, 4:55am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/3 "2020-04-17T04:55:49Z")
Hi Rene,
How can we configure vxlan. Could you please explain.
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### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [April 20, 2020, 9:06am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/4 "2020-04-20T09:06:26Z")
Hello Bikram
Take a look at the following lesson in order to further understand how to implement a VXLAN topology.
> **[VXLAN Flood and Learn with Multicast on Cisco IOS XE](https://networklessons.com/vxlan/vxlan-flood-and-learn-with-multicast-on-cisco-ios-xe)**
>
> This lesson explains how to configure VXLAN with Multicast PIM BI-DIR "flood and learn" on Cisco CSR1000V IOS XE devices.
I hope this has been helpful!
Laz
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### Author:  [@syedabrar\_8055](https://forum.networklessons.com/u/syedabrar_8055)
#### Post date: [June 8, 2020, 8:59pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/5 "2020-06-08T20:59:36Z")
This is the BEST explanation document on VXlan available on internet.
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### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [June 10, 2020, 11:50am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/6 "2020-06-10T11:50:42Z")
Hello Syed
Thanks so much for your positive feedback, it gives us the drive to continue to do our best!
Laz
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### Author:  [@tsignal32](https://forum.networklessons.com/u/tsignal32)
#### Post date: [June 10, 2020, 1:35pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/7 "2020-06-10T13:35:27Z")
I’m not sure if I posted this question to the correct topic area. My apology if I didn’t. I tried to access “Cisco CSR1000V VXLAN Unicast Configuration” a few minutes ago, but receive an error message. Below is the following error message from Firefox:
404 – Page not found
The page you trying to reach does not exist or has been moved. Please use the navigation menus, the search box, or try one of these instead:
Thanks
Tim
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### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [June 11, 2020, 6:32am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/8 "2020-06-11T06:32:29Z")
Hello Timothy
Thanks for taking the time to share this with us. Can you clarify from where you tried to access this content? There is no lesson called “Cisco CSR1000V VXLAN Unicast Configuration.” Can you send us the page from which you tried to connect to the failed link?
Thanks!
Laz
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### Author:  [@tsignal32](https://forum.networklessons.com/u/tsignal32)
#### Post date: [June 11, 2020, 12:49pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/9 "2020-06-11T12:49:40Z")
Laz,
Please see URL below.
[https://forum.networklessons.com/t/cisco-csr1000v-vxlan-unicast-configuration/11433](https://forum.networklessons.com/t/cisco-csr1000v-vxlan-unicast-configuration/11433)
I received periodic topic discussions via email, but for some reason when I click the link I’m unable to access.
Thanks
Tim
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### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [June 12, 2020, 5:29am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/10 "2020-06-12T05:29:21Z")
Hi Timothy
Thanks for sharing that, I’ll let @ReneMolenaar know.
Laz
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [June 17, 2020, 8:13am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/11 "2020-06-17T08:13:20Z")
I fixed this, somehow a draft post got published 🙂 Thanks for letting us know!
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### Author:  [@michael3.chung](https://forum.networklessons.com/u/michael3.chung)
#### Post date: [October 3, 2020, 1:27pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/12 "2020-10-03T13:27:19Z")
Hi
Thanks for this lesson.
\
My understanding is as follows. Could you please explain ?
1. Spine-leaf topology solved the Spanning tree issue. STP is not an issue in VxLAN.
2. Limited amount of VLANs : This is the essential why vxlan needs.
3. Large MAC address tables : I’am not sure how vxlan solve this problem. This issue is common in virtualization.
Spine-leaf was not ip network. It becomes ip underlay to bind MAC learning to a multicast group and to deliver VxLAN frame efficiently. Is it true ?
Thanks
Michael
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### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [October 6, 2020, 10:02am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/13 "2020-10-06T10:02:23Z")
Hello Michael
First of all, we must make a distinction between VXLAN and spine-leaf. The first is a tunnelling protocol while the second is a network topology/architecture. They can work together, but they don’t necessarily have to be implemented together.
> [@michael3.chung](#):
>
> - Spine-leaf topology solved the Spanning tree issue. STP is not an issue in VxLAN.
Actually, the spine-leaf topology doesn’t solve the inefficiency of STP. If you create an L2 spine-leaf topology, without any additional configuration parameters, STP will severely limit the available bandwidth. The solutions to the STP problem (regardless of the topology underneath) is:
- to employ VXLAN
- to break the network into smaller network segments/subnets
- to introduce what is known as Transparent Interconnection of Lots of Links (TRILL) or shortest path bridging (SPB) to replace STP.
You can choose which solution to use depending on your requirements and what your equipment supports.
> [@michael3.chung](#):
>
> - Limited amount of VLANs : This is the essential why vxlan needs.
This is one of the basic problems that VXLAN solves, allowing extensively large datacenters to have more than the 4096 VLANs that normal Ethernet provides.
> [@michael3.chung](#):
>
> 1. Large MAC address tables : I’am not sure how vxlan solve this problem. This issue is common in virtualization.
Because you are able to segment the datacenter network into tens of thousands of subnets, you can keep the number of hosts per subnet very small. The result is that the MAC address tables created for each subnet remain small.
> [@michael3.chung](#):
>
> Spine-leaf was not ip network. It becomes ip underlay to bind MAC learning to a multicast group and to deliver VxLAN frame efficiently. Is it true ?
Again, spine-leaf is a particular architecture, not necessarily associated with VXLAN. If you choose to use it, you can. If not, you don’t have to. But if you do, yes, it becomes the underlay routed network.
I hope this has been helpful!
Laz
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### Author:  [@iarca](https://forum.networklessons.com/u/iarca)
#### Post date: [November 16, 2020, 9:25pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/14 "2020-11-16T21:25:05Z")
Hello,
Thank you for the lesson. It is very informative. This is very new topic for me.
I have a question about VXLAN frame format. With those added headers, total MTU size should be beyond 1500bytes. How do VTEP devices handle this?
My other question is about Packet Walkthrough picture. It looks like in the picture Host1 is doing the tunneling and encapsulate the packet with the tunnel IP address. (192.168.12.101). Shouldn’t be the tunneling done by VTEP ?
Thank you.
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### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [November 18, 2020, 7:07am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/17 "2020-11-18T07:07:46Z")
Hello Ike
> [@iarca](#):
>
> With those added headers, total MTU size should be beyond 1500bytes. How do VTEP devices handle this?
That’s a very good observation, and yes, the underlay infrastructure must be configured in order to accommodate this overhead. The [VXLAN RFC draft](https://tools.ietf.org/html/draft-mahalingam-dutt-dcops-vxlan-08#page-10) states the following:
> VTEPs MUST not fragment VXLAN packets. Intermediate routers may
> fragment encapsulated VXLAN packets due to the larger frame size.
> The destination VTEP MAY silently discard such VXLAN fragments. To
> ensure end to end traffic delivery without fragmentation, it is
> RECOMMENDED that the MTUs (Maximum Transmission Units) across the
> physical network infrastructure be set to a value that accommodates
> the larger frame size due to the encapsulation. Other techniques
> like Path MTU discovery (see [RFC1191 and [RFC1981]) MAY be used to
> address this requirement as well.
Specifically, the underlay network must be able to accommodate at least 1554 bytes:
- 1518 (max) for the inner Ethernet frame
- 8 bytes for the VXLAN header
- 8 for the outer UDP header
- 20 bytes for the outer IPv4 header
> [@iarca](#):
>
> My other question is about Packet Walkthrough picture. It looks like in the picture Host1 is doing the tunneling and encapsulate the packet with the tunnel IP address. (192.168.12.101). Shouldn’t be the tunneling done by VTEP ?
Yes, you are correct, this seems to be a typo. I’ll let Rene know to correct this. Thanks for pointing that out!
I hope this has been helpful!
Laz
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [November 18, 2020, 8:02am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/18 "2020-11-18T08:02:37Z")
> [@iarca](#):
>
> My other question is about Packet Walkthrough picture. It looks like in the picture Host1 is doing the tunneling and encapsulate the packet with the tunnel IP address. (192.168.12.101). Shouldn’t be the tunneling done by VTEP ?
That is a typo indeed. I just fixed it, thanks!
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### Author:  [@iarca](https://forum.networklessons.com/u/iarca)
#### Post date: [November 18, 2020, 1:11pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/19 "2020-11-18T13:11:23Z")
Thank you very much Laz for the clarify the issue.
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### Author:  [@drorem](https://forum.networklessons.com/u/drorem)
#### Post date: [December 15, 2020, 10:56pm UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/20 "2020-12-15T22:56:44Z")
I believe there’s a typo in the diagram at 9:30 - the hosts IPs are shown as
192.168.1.101 should be → 192.168.12.101
192.168.2.102 should be → 192.168.12.102
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### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [December 17, 2020, 6:57am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/21 "2020-12-17T06:57:40Z")
Hello Doug
Thanks for pointing that out. I will let Rene know!
Laz
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### Author:  [@ramatemc](https://forum.networklessons.com/u/ramatemc)
#### Post date: [March 31, 2021, 5:16am UTC](https://forum.networklessons.com/t/introduction-to-virtual-extensible-lan-vxlan/9744/22 "2021-03-31T05:16:05Z")
Hi Team,
I joined as a member to understand basic concepts in networking. The lessons are really helpful.
Coming to VxLan, i have one query.
In multisite environment, generally Stretched VLANs are needed for some clusters. At same time, it is not recommended. So what i understood using VxLAN we can overcome this.
Using VxLAN, we encapsulate L2 Frame and transport over L3 network across sites. While encapsulate the L2 Frame , the VTEP (virtual Tunnel Endpoint) IP and mac will be added as header . However, VTEP IP addresses mentioned both in Source & Target sites also shown as in “Same IP segment”. That means without routing the frame will be forwarded across sites. This will be faster. Is this understanding of mine is correct?
Then again, we need to have same IP segment both in source and target site for VTEP Devices right? is this also stretched across sites right? This will conflict the basic idea of stretched IP segment (VLAN) across sites ? Can you help to clarify this concept.
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