Switching

Hello,

I would like to know if it is best practice to implement RSTP in a VC switches. in My design, i have ex3400 switches in a VC and they have uplinks connected towards QFX5110 switches that are also in VC. I would like to prevent loops in my network design. Also i have been investigating through forums/documentation how to implement RSTP in a VC. but i couldnt find the right answer. So I would apreciate some ideas how to aproach this.

1.If i understand correctly Junos does automatic detection of edge ports, when no BPDUs are received. Then this ports are automatically configured as edge ports?

2.Or are all ports non-edge by default unlles you configure them as edge ports. What if u dont want some ports(uplinks) to be edge ports do u leave it as default?

3. so back to my scenario, do i need to add all interfaces manually in ex3400 and QFX as edge port(RSTP) and enabling bdpu-block-on-edge, which will shut down an edge port that receives BPDUs ?. except the uplinks or ae intefaces towards srx?.

EX:

set protocols rstp interface ae2 edge

set protocols rstp interface ae3 edge
set protocols rstp bpdu-block-on-edge

QFX:

set protocols rstp interface xe-1/0/3 edge

set protocols rstp interface xe-2/0/3 edge
set protocols rstp bpdu-block-on-edge

4. what about the uplinks between the EX an QFX?, they should be participating in RSTP cause they will be advertising BPDUs towards each other (non-edge ports). what kind a configuration do i need to include them in the RSTP?, If i use the "mode point-to-point", will it make the uplinks ports as a non-edge ports?, are the ports link not already point-to-point by default?, if so, why do u still need to classify them as point-to-point in the configuration?.

EX:

set protocols rstp interface xe-1/0/0 mode point-to-point
set protocols rstp interface xe-2/0/0 mode point-to-point

QFX:

set protocols rstp interface et-1/0/4 mode point-to-point
set protocols rstp interface et-2/0/4 mode point-to-point

thanks.

Sul

In general with VC, RSTP is not required between VC pairs; defeats one of the purposes of VC.

Interfaces on Juniper EX switches are by default enabled for RSTP, but not Edge.  If you want Edge, then this must be explicity configured.  Using either Groups of interface-range, is easiest to implement.

#3 - correct.  Must be explicitly set on Edge (user) facing ports, and RSTP itself (never mind Edge all) should likely be disabled on inter-switch or uplink 'trunk-type' interfaces.

#4 - RTSP should very likely be disabled on these links.

HTH

Devices in VC do not need STP running between them.

All the ports connected to end hosts are to be configured as edge ports and enable bdpu-block-on-edge at the RSTP level to disable the ports configured as edge in case BPDU's are received on them. By default, Junos does automatic detection of edge ports but changes it to non-edge ports when BPDU's received on them. So manually configure and enable bdpu-block-on-edge would be good.

If both the EX-VC and QFX-VC are layer-2 bridges, then I think RSTP is necessary on the links connecting each other to avoid loops. Now the mode point-to-point is the default mode on full-duplex ports whereas on half-duplex it is shared mode.

Hope this helps.

Thanks and regards,

Pradeep Kumar M

Juniper CFTS.

"If both the EX-VC and QFX-VC are layer-2 bridges, then I think RSTP is necessary on the links connecting each other to avoid loops."

This is only true if there are multiple AE or single links between the VCs.  If it is 1 x AE with multiple links, RSTP is not required - big advantage of VC.  In VC each group of multiple switches acts and looks like a single switch.  If you connect two switches via a single connection (be it a single link or multiple links within a single AE) there is no loop.

Thank u guys, i understand now.

regarding configuration, so i can configure manually the end hosts as edge-ports, and afcause as mentioned before i will use group interface range.

EX/QFX

set protocols rstp interface ae2 edge

set protocols rstp interface ae3 edge

set protocols rstp interface ge-0/0/1 edge

set protocols rstp interface ge-0/0/2 edge
set protocols rstp bpdu-block-on-edge

So for the uplinks (trunk) between the switches, i dont need to add the trunk ports manually on RSTP?, it wil automatically check if BPDUs are send and it will change to non-edge port. just by adding edge ports on RSTP is enough?.

can someone please confirm this?.

Hello Suli,

Yes this would work. You would need to use edge-port configuration only on the user facing inerfaces as you do not want them to be participating in any STP election process.

So you can configure the following as you suggested (If they are going to end user devices such as servers, PCs etc)

set protocols rstp interface ae2 edge
set protocols rstp interface ae3 edge
set protocols rstp interface ge-0/0/1 edge
set protocols rstp interface ge-0/0/2 edge
set protocols rstp bpdu-block-on-edge

for the uplinks (trunk) between the switches, you dont need to add the trunk ports manually on RSTP as it wil automatically check all the ports.