Ethernet Switching
Ethernet Switching

RTG and STP

2 weeks ago

Hi There,

 

My question is a basic one: 

RSTP Instance 1 (Blu): RTG is configured so RSTP disabled for RTG links.

What about the BPDU coming from RSTP Instance 2 (yellow) fro example switch2?

Is the switch1 accepting the BPDU coming from switch 2?

Thanks.

 

RTG1.jpg

 

5 REPLIES 5
Ethernet Switching

Re: RTG and STP

2 weeks ago

Hi FabNewCert,

 

For this topology to work properly with RTG, you not only need to disable RSTP on Switch 1 ports part of RTG but also the interfaces towards Switch1 on both Switch 2 and Switch 3.  Here is a link explaining the recommendation in detail:

 

https://www.juniper.net/documentation/en_US/junos/topics/example/cfm-ex-series-redundant-trunk-group...

or (after redirection)

https://www.juniper.net/documentation/en_US/junos/topics/topic-map/redundant-trunk-groups.html#id-ex...

 

Hope this helps.

 

Regards,
-r.

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Ethernet Switching

Re: RTG and STP

2 weeks ago

Hi FabNewCert,

 

What mriyaz mentioned is correct and just to add you have to disable XSTP on the interfaces facing to the RTG switch, even though the RTG speakers drop XSTP BPDUs , the recommendation is to disable it to avoid extra processing ( generate and drop actions) at both sides.

 

Warm regards,

Pablo Restrepo -

Ethernet Switching

Re: RTG and STP

2 weeks ago

Hi FabNewCart

 

To configure the RTG on switch 2 and switch 3 you have to completely disable the rstp on the respective interfaces connecting towards the RTG switch 1. So you may not put those interface in any rstp instance. Hence those interfaces on switch 2 and switch 3 would never generate any bpdu towards switch 1. 

However you may run the rstp on other interfaces on switch 2 and switch 3 which would work as expected.

 

Ethernet Switching

Re: RTG and STP

2 weeks ago

Hi 

 

To answer your question :

 

1>What about the BPDU coming from RSTP Instance 2 (yellow) fro example switch2?

incase of RTG that is configured from the blue side to the yellow side ,

when RTG is configured only the Data traffic is blocked , other control traffic will flow through the switch 

for faster convergency it is recommended to disable stp on those ports only that is involved in RTG on both the sides of the link

 

2>Is the switch1 accepting the BPDU coming from switch 2?

STP needs to be disabled 

Ethernet Switching

Re: RTG and STP

2 weeks ago

Hi 

 

To answer your question :

 

1>What about the BPDU coming from RSTP Instance 2 (yellow) fro example switch2?

In case of RTG only the data traffic is blocked on the secondary link , but the control traffic flows through the secondary link 

but for faster converence it is recommended to disable STP only on those ports for uninterrupted traffic 

 

2> Is the switch1 accepting the BPDU coming from switch 2?

if RSTP is enabled on those ports yes it will accept it on those ports also 

but you need to keep is disabled 

 

Regards

Sharanya