Question

Fabric attach - SMLT with LACP

  • 27 January 2021
  • 8 replies
  • 211 views

Hello,

 

I am trying to connect a x460G2 stack to a VSP7400 cluster using this configuration with no luck.

While both links are up on both sides communication is not happening.

x460G2

enable sharing 1:49 grouping 1:49,2:29 algorithm address-based L2 lacp

 

VSP7400 config is identical on both cluster members

mlt 3 enable
mlt 3 member 1/3
mlt 3 encapsulation dot1q


interface mlt 3
smlt
fa
fa enable
no fa message-authentication
exit

lacp smlt-sys-id 20:9e:f7:8f:6c:03
lacp enable

interface GigabitEthernet 1/3
default-vlan-id 0
no shutdown
lacp key 3 aggregation enable timeout-time short
no spanning-tree mstp  force-port-state enable
exit

What am I missing?

 

Thank you,

Klaus


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8 replies

Userlevel 7
Badge +1

Hello Klaus,

I notice that in the commands you write "lacp key <key>" is missing on the MLT interface.
The lacp key "glues" the components together so it must be the same on the port and on the MLT.

In addititon I can’t see the FA part on the XOS site.

If this is not enough. Please send the output of
show mlt
show log file

with the corresponding lines.

 

Here are the steps for SMLT and LACP also in detail listed:

https://extremeportal.force.com/ExtrArticleDetail?an=000083501&q=vsp%20smlt%20lacp

and here FA with VSP and XOS:

https://extremeportal.force.com/ExtrArticleDetail?an=000077283&q=fabric%20attach%20x440

 

Userlevel 6
Badge +1

Hi Klaus,

 

You cannot mix MLT and LACP.

If you go for MLT, you need to add port members.

If you go for LACP, you need to define the lacp key as mentioned by Stephan.

Here below a config abstract from a production VSP connecting to Cisco switches in LACP:

#

# MLT CONFIGURATION

#

mlt 203 enable name MLT-Unit-2-Port-03

mlt 203 encapsulation dot1q

interface mlt 203

smlt

lacp enable key 203

exit

#

# VLAN CONFIGURATION

#

vlan mlt 100 203

vlan mlt 101 203

vlan mlt 110 203

vlan mlt 115 203

vlan mlt 246 203

# PORT CONFIGURATION - PHASE II

#

interface GigabitEthernet 2/3

lacp key 203 aggregation enable

lacp enable

exit

 

 

Mig

Hi Stephan, Mig,

 

Thank you for your support - it’s much appreciated.

Put my glasses on and did more RTFM and it’s working now :grinning: .

Having an MLT and no port members was confusing me.

 

So now that it’s working with LACP, is there an advantage of having LACP instead of just a static port bundle which allows me to use SLPP?

Our SE pointed out that LACP is another protocol that has to come up and requires troubleshooting.

 

Your thoughts?

 

Klaus

Userlevel 7
Badge +1

Hello Klaus,

an advantage of LACP is e.g. that it checks if the remote side is also a LACP link, this prevents a loop if the remote side is not configured for LAG but the cables (more the one) are already plugged and the ports are up.

In this case on your VOSS tyou will see for example this message in the LOG: 
“INFO A churn condition has been detected for port <port> as the PARTNER is out of sync”

Furthermore it is also prevented that one side sends packets although the other side is still booting and has not started all processes yet, but the link is already up.  Only if the LACP communication works everything is clear for the data transmission and both partners also send data.

 

Userlevel 6
Badge +1

Hi Klaus,

On top of the advantages mentioned by Stephan I would like to add another one that can make the difference.

If you configure ports 1 & 2 with lacp key 201 and port 3 & 4 with lacp key 203 you protect yourself from wrong patching.

If by mistake you mix the patches from port 1,2 and 3,4, the LACP cannot come up  on the faulty cable because the keys will not match on cables coming from different LACP links.

It is like playing with the ethertype (or other parameters) when configuring VLACP.

Mig

Hi Stephan, Mig,

 

Thank you again for sharing your knowledge.

Just confirming that today it saved my back when the link didn’t come up due to a key mismatch.

 

Klaus

Userlevel 6
Badge +1

:metal:

Userlevel 7
Badge +1

Hello Klaus,

glad if we could help. Thank you for your feedback.