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Author Topic: Few simple and random questions about MLT/SMLT  (Read 5192 times)

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Offline bellec

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Few simple and random questions about MLT/SMLT
« on: November 12, 2014, 11:09:47 AM »
Hello,

I'm currently modernizing my network infrastructure.
I have currently two ERS-5530 core stack (2 switch per stack) which are connected with a simple DMLT. I'll add an IST over this.

Then, I plan to install another stack which will be connected to my core stack (the ERS-5530 with IST).

In a wonderful world, I would have choose the ERS-5000 for the new stack in order to plug it the core switch via SMLT. But it cost money, SMLT seems rather complicated to install, and I don't need the extra bandwidth provided by SMLT.

So I plan to install an ERS-4500 stack (2 switch) which will be connected to the 5530s via DMLT. So one DMLT link in the first 5530 stack, and another DMLT link to the second 5530 stack.

If I have correctly understood, I will need to configure SLPP Guard on these two DMLT links, and one of them will be inactive until the other fails ? The two DMLT links cannot works in the same time, right ?

Another question, can I do a DMLT link with a 100 Mbits port and another at 1000 Mbps ? I know that LACP can't do that.

I have read that IST needs an extra license ? Is that right ? And if so, is there a way to see if I have such a license on my current switch ?

Is there some IST, MLT or SMLT implementation limitations ? For instance, can I do a SMLT infrastructure with only 3 switch (not stack ! switch) ?

Regards.


Offline Telair

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Re: Few simple and random questions about MLT/SMLT
« Reply #1 on: November 12, 2014, 03:22:18 PM »
Once you have your two stacks IST'ed together SMLT is a snap.  Almost nothing more to it than to setup a DMLT link.  As to you other questions though...

"If I have correctly understood, I will need to configure SLPP Guard on these two DMLT links, and one of them will be inactive until the other fails ? The two DMLT links cannot works in the same time, right ?"

- OK, so we have one cable going back to core stack #1 and one cable going to core stack #2?  As long as those core stacks are IST'ed together and you configure the links as an Single Port SMLT on each core stack , both links forward traffic no problem.  No need for SLPP guard.  As far as the 4500 stack is concerned, it is connecting to another switch via MLT and doesn't know it's an SMLT cluster.

"Another question, can I do a DMLT link with a 100 Mbits port and another at 1000 Mbps ?"

- No.  All ports in an MLT group have to be the same speed.  They can be different media types (one copper, one fiber), but only one speed.

"I have read that IST needs an extra license ? Is that right ? And if so, is there a way to see if I have such a license on my current switch ?"

- Yes, an "Advanced License" or "Premier License" is required to enable switch clustering as well as  SMLT, OSPF, ECMP, VRRP, and PIM-SM.  The "Premier License" enables VRF-Lite in addition to all the advanced features.  On the switch CLI you can use the command "show license all" to view the installed licenses or in EDM under "Edit" -> "File System" -> "License File" tab.  It says what licenses are installed.

"Is there some IST, MLT or SMLT implementation limitations ? For instance, can I do a SMLT infrastructure with only 3 switch (not stack ! switch) ?"

- You can have two single switches clustered with each other running an SMLT link to a third switch no problem so that it looks like a triangle.  There are limitations to MLT.  You can't have more than 8 links in a single MLT group last time I looked it up.  All the links have to be the same speed and duplex.  The SMLTSysID has to be the same on both clustered switches/stacks.  Not a rule, but it's always a good idea to run VLACP on your MLT links as long as they connect to another Nortel/Avaya switch on the other side.

Hope that answers some of your questions.

Offline bellec

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Re: Few simple and random questions about MLT/SMLT
« Reply #2 on: November 12, 2014, 03:54:04 PM »
- Yes, an "Advanced License" or "Premier License" is required to enable switch clustering as well as  SMLT, OSPF, ECMP, VRRP, and PIM-SM.  The "Premier License" enables VRF-Lite in addition to all the advanced features.  On the switch CLI you can use the command "show license all" to view the installed licenses or in EDM under "Edit" -> "File System" -> "License File" tab.  It says what licenses are installed.
OK, I already have VRRP enabled so I guess it's OK, but I will check with the command you provided.

Once you have your two stacks IST'ed together SMLT is a snap.  Almost nothing more to it than to setup a DMLT link.  As to you other questions though...
OK, I will recondsider. But SMLT is not supported on the ERS-4500 series, right ?

Hope that answers some of your questions.
Yes it helps me a lot, thanks !

Offline Telair

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Re: Few simple and random questions about MLT/SMLT
« Reply #3 on: November 12, 2014, 04:01:38 PM »
"OK, I will recondsider. But SMLT is not supported on the ERS-4500 series, right ?"

- Correct.  Only 5500/5600 switches can cluster together with IST links.  4500's with advanced licenses can do OSPF, VRRP & ECMP, but no SMLT or clustering.  That's reserved for the 5500/5600's.  The way I read things was your core was going to be two 5530 stacks IST'ed together and the 4500 stack was going to be on the edge.

If it's useful to you, here is Avaya's 2014 licensing guide.  It tells you what licenses are available for what equipment and what it does.

https://downloads.avaya.com/css/P8/documents/100123702

Offline bellec

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Re: Few simple and random questions about MLT/SMLT
« Reply #4 on: November 12, 2014, 04:57:10 PM »
The way I read things was your core was going to be two 5530 stacks IST'ed together and the 4500 stack was going to be on the edge.
Absolutely. I wanted to connec the 4500 stack to the core by SMLT (in a triangle fashion), but it's then not possible (need 5500/5600 for that). So I was wondering what happened if I instead connect the 4500 stack with two MLT link (one to each stack of the core IST). There will be a loop ?

If it's useful to you, here is Avaya's 2014 licensing guide.  It tells you what licenses are available for what equipment and what it does.
Thanks for the link, it's an interesting lecture indeed.

Offline Telair

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Re: Few simple and random questions about MLT/SMLT
« Reply #5 on: November 12, 2014, 05:06:19 PM »
"Absolutely. I wanted to connec the 4500 stack to the core by SMLT (in a triangle fashion), but it's then not possible (need 5500/5600 for that). So I was wondering what happened if I instead connect the 4500 stack with two MLT link (one to each stack of the core IST). There will be a loop ?"

- The core needs to be 5500/5600's as they can do SMLT, but the edge switch can be anything that understands the MLT protocol (2500's all the way up to 5600's).  So your 4500 stack will work just fine.  The 4500 gets configured like it's connecting back to another switch via MLT.  It just doesn't know the other switch is two clustered 5530's in your case.  The 5530 cluster has one link to each side of the cluster and you configure the MLT as a SMLT link with the same ID# and VLAN's on each side.  There is no looping as both sides understand the multiple links act as a single link.  Both links send and receive traffic, no problem.

Offline Dominik

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Re: Few simple and random questions about MLT/SMLT
« Reply #6 on: November 13, 2014, 02:45:03 AM »
On your ERS4500 you just configure one MLT for example with 4 Links.
Than you connect 2 of these links to the first ERS5530 and the other 2 links to the second ERS5530.
You can think of it like your two ERS5530 with an configured SMLT will show up to your ERS4500 Stack like one big siwtch. So you have no problems here with a loop. The main benefit for an IST/SMLT setup in the core is that the two ERS5530 will stay indepented, so you can do a sofware update of one of your ERS5530 with interrupting the traffic in your network.
With a stack you have also merged together multiple physical boxes to one logical box.
The downside of the stack is that you can only do a software update to all physical devices in your stack with one procedure, wich will resultate in downtime for all connected boxes.

Cheers

PS
it is possible to configure an SMLT on the ERS5000 switches with different portspeeds like 100 and 1000
but that is a not recommanded configuration and I would not use it in a production network
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Offline bellec

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Re: Few simple and random questions about MLT/SMLT
« Reply #7 on: November 13, 2014, 03:54:33 AM »
OK, thanks all for your explanation. I now understand how SMLT works.

Offline bellec

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Re: Few simple and random questions about MLT/SMLT
« Reply #8 on: November 19, 2014, 04:16:45 AM »
Hello again,

I read the Avaya documentation NN47200-502 (title "Configuration — VLANs, Spanning Tree, and Link Aggregation Avaya Ethernet Routing Switch 5000 Series") and I see two surprising facts :

1) The SMLT aggregation switches can be a single switch or a stack. There is no restriction on the number of units in the SMLT stack, but for better recovery in case of failure, the stack should contain at least three units. If you use a stack of just two units, one unit leaving the stack leaves two isolated single units because all IST, SMLT, and SLT ports on these two units is disabled. For fastest recovery, SMLT should have at least one link connected to the base unit.

I don't really understand why I should have 3 units for better recovery.
Let's say I have 2 stacks (A and B) of 2 switch (a1, a2, b1 and b2).
A and B are aggregated in an IST.
a1 and b1 are respective base-unit.
If a1 is now down for any reason, I guess that a2 will become quickly the temporary base-unit and the IST and all SMLT should works without problem nor failure ?

2) In a stack, the SMLT can be active only on the base unit or the temporary base unit, and it is solely responsible for the peer to peer switch communication. In stack mode, only the base unit or the temporary base unit can take ownership of the SMLT IST operations.

Do I really understand ?! If I configured an SMLT path between the IST core and an edge switch, only the SMLT links connected on the base-units of the IST are active ? The others links are disabled until the base-unit fails ?

Regards.

Offline Dominik

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Re: Few simple and random questions about MLT/SMLT
« Reply #9 on: November 19, 2014, 08:17:59 AM »
@1)
Yes you can do a switchclsuter as discribed with two times a 3 unit stack.
I am not a fan of that configuration, I prefer to use a single unit for an switchclsuter core.
It is supported from Avaya you can do it up to 8 units but you are dealing with two different technologies to achieve redundancy. So it is more complex and more crazy things can happen.

@2)
It means the base unit is handling the IST and logic. You can use all ports of your stack for SMLT links.
So it can happen that you have a higher CPU utilization on your base unit, in fact it has to process more than the other units in the stack.
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Offline bellec

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Re: Few simple and random questions about MLT/SMLT
« Reply #10 on: November 20, 2014, 06:20:17 AM »
OK, thanks for your answer.
I also found the document NN48500-584 which describe these points actually.