Switching

Hi all,

May i know whether the MC-LAG and RSTP can coexists at same time? If yes then is it the back-to-back between Spine / Core Switch need to participate in RSTP also?

Thanks and appreciate any feedback

Hello kronicklez

STP has to be disabled in the ICL, however if your downstream device is a switch, you should configure stp on the mc-ae interfaces with the lowest priority to make the MC peers the root bridge.

If your downstream device is a host/server, you should configure the mc-aes as edge ports.

Regards,

Hi rbabraham,

As i'm understand, on RSTP between Core/Spine that interface must need to participate in RSTP protocol. If that back-to-back link (iccp) not participate in RSTP then loop will happen right?

Lets say i have two access switch. ASW-1 (two link) is LAG to Core  and ASW-2 (two link) is just RSTP to Core.

https://www.juniper.net/documentation/en_US/junos/topics/topic-map/spanning-tree-configuring-rstp.html

Thanks and appreciate your feedback

kronicklez,

Between the MC-LAG peers we'll have the ICCP protocol and the ICL link. You can have them both through the same physical link or in two different physical links.

If you have the ICCP protocol over the ICL link, you don't need RSTP, because the ICL doesn't allow arp/mac learning, then a spanning tree protocol is not required because no loop will be formed. 

In the other hand, if you have two Switches as downstream devices, it is recommended to enable RSTP in both MC-AEs and on the downstream device as well. 

The MC-LAG peers should be the root bridge

Regards,

Hi rbabraham,

yes, i'm use ICCP protocol using ICL link. So u means for example the ae0 (back-to-back trunk) dont need to assign under RSTP stanza?

Do u have any other doc as reference coz it look like mandatory the back-to-back participate in RSTP as url given previously. Previously i have made loop using EX9200 due to forget the back-to-back interface participate in the RSTP .

Thanks and appreciate any feedback

Hi kronicklez

Correct the ICL doesn't need RSTP. Please check the following link with MC-LAG best practices

• Configure STP globally so that STP can detect local miswiring within and across MC-LAG peers.

• Disable STP on ICL links, however, because STP might block ICL interfaces and disable protection.

https://www.juniper.net/documentation/en_US/junos/topics/concept/best-practices-usage-notes.html

Hi rbabraham,

I'm check on latest url that u given. Based on url below if my Spine/Core is using MX (currently i'm test using vMX version 18.4R2.7) it dont have command "set protocols rstp interface ae0 disable" . So how to make sure the ICL link not participate in RSTP if we cannot apply knob as highlated?

https://www.juniper.net/documentation/en_US/junos/topics/topic-map/examples-mc-lag.html

Thanks and appreciate your feedback

You only specify the interfaces that do participate.

set protocols rstp interface ae1
set protocols rstp interface ae2
set protocols rstp interface ae3
set protocols rstp interface ae4
set protocols rstp interface ae5
...

Hi all,

Thanks for all the input.