# I need some quick topic Underlay, Overlay and GET VPN

**URL:** <https://forum.networklessons.com/t/i-need-some-quick-topic-underlay-overlay-and-get-vpn/2994>\
**Category:** ASA\
**Created:** [February 20, 2018, 1:54pm UTC](https://forum.networklessons.com/t/i-need-some-quick-topic-underlay-overlay-and-get-vpn/2994 "2018-02-20T13:54:30Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![ccnp.manami](https://cdn-forum.networklessons.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@ccnp.manami](https://forum.networklessons.com/u/ccnp.manami)\
**Post date:** [February 20, 2018, 1:54pm UTC](https://forum.networklessons.com/t/i-need-some-quick-topic-underlay-overlay-and-get-vpn/2994/1 "2018-02-20T13:54:30Z")

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Hi Rene,

Can you please help me to understand three topics. I need to implement something related to these three in my company.

1. What is underlay?
2. What is overlay?
3. and GET VPN

I need to implement one GET VPN Client in MPLS VPN network.

Regards,  
Manami

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**Author:** ![ReneMolenaar](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/renemolenaar/32/488_2.png) [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)\
**Post date:** [March 5, 2018, 1:13pm UTC](https://forum.networklessons.com/t/i-need-some-quick-topic-underlay-overlay-and-get-vpn/2994/2 "2018-03-05T13:13:20Z")

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Hi Manami,

An overlay network is usually a virtual network that runs of top of an underlying network, the underlay.

For example, look at DMVPN:

> **[Introduction to DMVPN](https://networklessons.com/vpn/introduction-to-dmvpn)**
>
> This lesson explains how DMVPN (Dynamic Multipoint VPN) uses GRE multipoint and the difference between phase 1,2 and 3.

The DMVPN tunnels are the overlay network, the underlay is the network with the Internet connections.

GET VPN is still on my list to create a lesson for, it’s a bit too detailed to explain in a few words here.

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<div class="post-metadata">

**Author:** ![ccnp.manami](https://cdn-forum.networklessons.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@ccnp.manami](https://forum.networklessons.com/u/ccnp.manami)\
**Post date:** [March 6, 2018, 4:06pm UTC](https://forum.networklessons.com/t/i-need-some-quick-topic-underlay-overlay-and-get-vpn/2994/3 "2018-03-06T16:06:57Z")

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Hi Rene,

Can I have an example of Overlay Network? Why do we need a virtual network that runs of top of an underlying network like DMVPN?

Regards,  
Manami

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**Author:** ![ReneMolenaar](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/renemolenaar/32/488_2.png) [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)\
**Post date:** [March 7, 2018, 7:17am UTC](https://forum.networklessons.com/t/i-need-some-quick-topic-underlay-overlay-and-get-vpn/2994/4 "2018-03-07T07:17:48Z")

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Hi Manami,

DMVPN is the overlay (the virtual network), the underlying network is the infrastructure you use for perhaps Internet connectivity.

Rene

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<div class="post-metadata">

**Author:** ![ccnp.manami](https://cdn-forum.networklessons.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@ccnp.manami](https://forum.networklessons.com/u/ccnp.manami)\
**Post date:** [March 9, 2018, 5:18pm UTC](https://forum.networklessons.com/t/i-need-some-quick-topic-underlay-overlay-and-get-vpn/2994/5 "2018-03-09T17:18:38Z")

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I understand.

Thank you.  
Manami