Reasons for MLAG on Summits

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Hello, everybody!

I am an engineer at partner company and we are going to make a business event for our customers. My presentation is about MLAG on BD8806 with VRRP. 

I suppose that I will be asked a question about why there is MLAG on Summit Switches, which could be stacked easily?

Could you please give me some ideas?

Many thanks in advance,

Ilya
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Ilya Semenov

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Posted 2 years ago

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André Herkenrath, Employee

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It's about downtime. When you upgrade a stack, the whole stack must be rebooted. When you upgrade a pair of MLAG-Switches you can upgrade and reboot one by one. With the right design you can achieve a always up core.

Andre
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Rui Marques

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Besides what André already said, When you stack, the control of the stack is made only by the master control plane. The other switches are serving only the ports. On a MLAG configuration, both control planes are active and processing, so load is shared, and processing capability is added.
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Steven Lin, Employee

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The MLAG feature allows you to combine ports on two switches to form a single logical connection to another network device. The other network device can be either a server or a switch that is separately configured with a regular LAG
to form the port aggregation.
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Ilya Semenov

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The MLAG feature allows you to combine ports on two switches to form a single logical connection to another network device.

Why couldn't I do the same with etherchannel? Make 2-summits stack and give a link from both to a required host. At host's side configure teaming or NIC bonding.

I don't understand the diffrence, please, explain.
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Steven Lin, Employee

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MLAG could support more complex scenario, and sometimes switches not Compatibility for stacking in your scenario.
(Edited)
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Tripathy, Priya Ranjan, ESE

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Apart from the above features there are also single-tier MLAG which provides the redundancy at the access level.
Second is the  two-tier MLAG design provides the redundancy at the distribution level or the core-level. 
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Ilya Semenov

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Hello, could you please explain it in details?

"single-tier MLAG which provides the redundancy at the access level."

and

"Second is the  two-tier MLAG design provides the redundancy at the distribution level or the core-level. "

Many thanks in advance,

Ilya
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Erik Auerswald, Embassador

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You can even use two SummitStacks to create an MLAG pair. Stacking and MLAG are complementary features.
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Ilya Semenov

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Hello, Eric!

But why if I can connect two stacks via Etherchannel. This is much easily...
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Erik Auerswald, Embassador

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Hi Ilya,

for example, you can use 8 switches to form 4 MLAG pairs, or you can use two stacks of 4 switches each and create one MLAG pair.

Stacking can be viewed as a method to create a chassis-like virtual switch using standalone switches.

MLAG allows to connect one downstream device, e.g. a server, to two independent upstream devices using port sharing (aka LAG or port-channel).

Why would you set up MLAG between two chassis switches, if you can more easily use two modules inside the chassis for redundant connections?

Erik
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Tripathy, Priya Ranjan, ESE

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Please find below this article link which explains the two tier MLAG design in details:

https://gtacknowledge.extremenetworks.com/articles/How_To/Sample-configuration-for-two-tier-MLAG/?q=...
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Kawawa, GTAC

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This very question was asked about a year ago and I believe there are some very insightful responses that came from the community.  I hope the following thread can help answer your questions: https://community.extremenetworks.com/extreme/topics/mlag-vs-stack-what-am-i-missing