SMLT and MLT VLAN + LACP configuration confusion

[Anonymous]

Hi,

Hoping someone can provide some assistance in understanding SMLT / MLT configuration on a VSP8600.

I have a scenario where I’m migrating some EOS cores with VSPs one at a time, and I initially need to support STP to the egde. 

To do this I initially have to configure the first replacement core MLT’s as normal MLT’s and later move them to SMLT as and when both cores have been replaced and I can make use of SMLT, and STP is no linger important.

The part that is confusing me is the VLAN assignment against the MLT, here is an example of this when using SMLT in the EDM:

And similar output from a ‘show mlt’

====================================================================================================
                                    Mlt Info
====================================================================================================
                        PORT    MLT   MLT        PORT         VLAN
MLTID IFINDEX NAME      TYPE   ADMIN CURRENT    MEMBERS       IDS
----------------------------------------------------------------------------------------------------
4   6147  MLT-4        trunk   smlt   norm                       119 121 305 400 502 512 513 515 516 520 541 560 561 570 670
5   6148  MLT-5        trunk   smlt   norm                       119 121 306 401 502 512 513 515 516 520 560 561 570 670
6   6149  MLT-6        trunk   smlt   norm                       119 121 307 402 502 512 513 515 516 520 560 561 570 670
7   6150  MLT-7        trunk   smlt   norm                       119 121 308 403 502 512 513 515 516 520 560 561 570 670
8   6151  MLT-8        trunk   smlt   norm                       119 121 309 404 502 512 513 515 516 520 560 561 570 670
9   6152  MLT-9        trunk   smlt   norm                       119 121 310 405 502 512 513 515 516 520 560 561 570 670
10  6153  MLT-10       trunk   smlt   norm                       119 121 311 406 502 512 513 515 516 520 523 560 561 570 670
11  6154  MLT-11       trunk   smlt   norm                       119 121 312 407 502 512 513 515 516 520 523 560 561 570 670
12  6155  MLT-12       trunk   smlt   norm                       119 121 313 408 502 512 513 515 516 520 523 560 561 570 670
13  6156  MLT-13       trunk   smlt   norm                       119 121 314 409 502 512 513 515 516 520 522 560 561 570 670
14  6157  MLT-14       trunk   smlt   norm                       119 121 315 410 502 512 513 515 516 520 522 560 561 570 670
15  6158  MLT-15       trunk   smlt   norm                       119 121 316 411 502 512 513 515 516 520 560 561 570 670
16  6159  MLT-16       trunk   smlt   norm                       119 121 317 412 502 512 513 515 516 520 560 561 570 670

What I can’t see is where in the configuration is the association of VLAN’s to MLT?

You can add VLANs to an MLT with the config line ‘MLT 52 add 101” but nothing in the config that relates to it?

Why this is more baffling is when converting the SMLT interface to a normal MLT.

Take this example of MLT 64 below. This was originally a SMLT interface but since converting to a normalMLT it has stripped off the VLAN associations that where present previously against the MLT , and changed the portype to access?:

Then when I bring the interface up it changes the port type back to trunk and adds the VLANs to list:

This is problematic for me, as I will need to change all the interfaces to MLT and then change them back to SMLT, and I can;t find in the config where its relating the VLANs to the MLT / SMLT. This is a problem because of the convoluted config changes detailed below and because the information I was cross referencing to make sure all still correct has disappeared.

I assume its using the VLANs associated to the port, but if their is more than one port in the MLT, which one does it use (should be the same assignments, but curious).

Why would VLANs show against an MLT that is an SMLT but not a normalMLT?

Why when initially configuring the MLT you use “VLAN member add <VLAN ID> <Port Number>”. Only when the interface is up can you then use MLT <MLT ID> <VLAN ID> , maybe this is where the confusion is coming in, on top of using LACP.

When is STP going to be supported on a SMLT, if this was the case I would not need to do the conversion from SMLT to MLT?

To make this even more complicated the MLT / SMLT are configured to use LACP, so its additionally difficult to see what ports belong to what MLT  or in the case of an MLT, what VLANs belong to the MLT until its active (which is a little late).

Additionally I have to keep disabling LACP to add the VLANs (before they are up), and then re-adding it again.

The configuration would go something along the lines of:

interface mlt 64
 no smlt
 exit
interface gigabitethernet 2/5
 spanning-tree mstp force-port-state enable
 exit

To convert back from normalMLT to SMLT when adding other VSP core in:

interface mlt 64
 smlt
 no lacp enable
 exit
mlt 64 encap dot1q

I then need to Individually add each of the VLANs back onto the MLT as before and run the following

interface mlt 64
 lacp enable

The process is so convoluted and time consuming, I had to keep a track of, so throwing it out there. Maybe I’m doing it wrong, maybe there is a better way of doing it?

Look forward to hearing, and thanks in advance.

[Anonymous]

Thanks John for the info, and again your time, very much appreciated. Will certainly do a little more reading.

Based predominantly on the fact I am using LACP and your point 2, the suggestion is I first need put the switch in, connect it all up, bring up the interfaces and then configure the VLANs.

I obviously need to do all the configuration before the event. I think its the introduction of LACP is perhaps at the root of the configuration query.

At this time I’m doing the procedure below because the switch is using LACP and isn’t currently connected to anything, its the only method I found to get the config in place before the interface / port / MLT is up:

The configuration would go something along the lines first to convert a SMLT to a normalMLT. At this point I don’t seem to need to use the MLT <MLT ID> <VLAN ID> command because it pulls the VLANs from the port assignment. The normalMLT comes up (as per the EDM captures above) and dynamically assigns the ports and the VLANs:

interface mlt 64
 no smlt
 exit
interface gigabitethernet 2/5
 spanning-tree mstp force-port-state enable
 exit

To convert back from normalMLT to SMLT. I have to disable LACP to be able to use the MLT <MLT ID> <VLAN ID> command, as to why I have to use this command and disable LACP is still up for question when a normalMLT doesn’t require it:

interface mlt 64
 smlt
 no lacp enable
 exit
mlt 64 encap dot1q

I then need to Individually add each of the VLANs back onto the MLT as before and run the following

interface mlt 64
 lacp enable

Many thanks

[John_Hopkins · Accepted solution]

Hi Martin,

1. Not sure how i can say it more plainly but when working with MLT or SMLT i recommend you always add vlans to the MLT/SMLT.
2. You don’t have to disable LACP to associate a VLAN to the port. As per 1 don’t associate the vlan to a port if using an lacp-controlled MLT/SMLT. The following shows dynamically adding vlan 99 to lacp-controlled mlt 5 that previously had only vlan 100 on it. Make sure the ports are up and you should see something like this.
    

   AUH-COR1:1(config)#show mlt 
   ================= output abbreviated =========================
                          PORT    MLT   MLT        PORT         VLAN
   MLTID IFINDEX NAME      TYPE   ADMIN CURRENT    MEMBERS       IDS
   ----------------------------------------------------------------------------------------------------
   5   6148  LACP         trunk   smlt   smlt     1/11              100

   AUH-COR1:1(config)#mlt 5 vlan 99
   AUH-COR1:1(config)#show mlt
   ================= output abbreviated =========================
                          PORT    MLT   MLT        PORT         VLAN
   MLTID IFINDEX NAME      TYPE   ADMIN CURRENT    MEMBERS       IDS
   ----------------------------------------------------------------------------------------------------
   5   6148  LACP         trunk   smlt   smlt     1/11              99 100

3. If you were using static mlag (i.e. “mlt <mltid> member <ports>”) then you would see the “vlan mlt <vid> <mltid>” commands in the running and saved config. But it is just different when using a dynamic (i.e. lacp-controlled) MLT/SMLT. I don’t want to debate how it could be in an ideal world when the aim is to get it working this week.

This is the latest documentation: Configuring Link Aggregation, MLT, SMLT and vIST for VOSS 8.1

[Anonymous]

Thanks again for replying John, appreciate spending the time on it.

Still seems odd to me; as an example Cisco use Port-channel, EOS use lag.x.x, EXOS use shared ports, in each case each details in configuration the VLANs associated to the aggregate interface.

Even VOSS seems to do this similarly with the command MLT <MLT ID> <VLAN ID> but fails to reference it in configuration i.e. under the config ‘interface MLT xx’ I might expect to see the VLAN ID’s input with that command.

With not having the reference in configuration how could you restore that same configuration i.e. if there is no reference to the VLAN ID against the MLT how would it know to restore it? 

Why also if LACP is configured do I have to disable LACP to associate the VLAN to a port, or have to bring up the interface and then use the command MLT <MLT ID> <VLAN ID>. Why not just associate the VLAN to MLT, end of?

It would make sense to me to just add VLANs to an MLT and reference that in configuration?

My thoughts are maybe the command MLT <MLT ID> <VLAN ID> actually adds the VLANs to the ports under the hood, so effectively just using the command ‘VLAN members add 2/15’ if that was the sole port of that MLT. The reason when using LACP that you need the command MLT <MLT ID> <VLAN ID> is that the dynamic port needs to be up and ports known to form that MLT so that it knows what ports to the apply the VLANs to?

That leads me to think that if the MLT isn’t up, then so long as the interfaces have the same VLAN configuration then that will work, no need to use the command MLT <MLT ID> <VLAN ID>?

its odd though, is the reference of VLANs to MLT’s as in the EDM screenshot above, which infurs you must use the command (MLT <MLT ID> <VLAN ID>) prior in order to configure it, but leads me full circle in that can;t be right otherwise how do you restore an invisible command!?

Feel I’m babbling, but hopefully I getting the point across so I can understand fully.

Thanks

[John_Hopkins]

HI Martin, I would always use the  “mlt <x> vlan <y>” command for adding Vlans to the LACP-controlled MLTs or SMLTs. Keep a text file with those commands. If you convert an MLT to an SMLT and lose the vlan association you can quickly paste those commands back in. 

Note also the following statement at the bottom of page 23 of “Configuring Link Aggregation, MLT, SMLT, and vIST on Avaya Virtual Services Platform 7200 Series and...” about adding VLANs to a dynamic (lacp-controlled) MLT should any ports be inactive. So when you convert to SMLT, verify all links are up before using your file of  “mlt <x> vlan <y>” commands.

When you add a VLAN to a dynamic MLT, only the active ports of the MLT are added as port

members of the VLAN. Ports configured with the same aggregation key, but not active, are not

added to the VLAN. If these inactive ports become active later, the system does not automatically

add them to the VLAN port member list.