Switching

Hello to All,

Topic: stp interoperability between cisco and ex swithc.

ref: https://www.juniper.net/us/en/local/pdf/implementation-guides/8010002-en.pdf

I already read different forum and juniper  documentation about this topic and at the end it is valid that:

1)cisco side -> pvstp

2)ex side -> rstp

The above combination should work just fine (except in changing the path cost calculation cisco´s side )

Based on https://www.juniper.net/us/en/local/pdf/implementation-guides/8010002-en.pdf, what is happening is that:

1) juniper´s side simply ignore the bpdu-pvstp sent by the cisco  and consider them like normal multicast traffic. 

2) juniper´s side is recognizing as standard bpdu the muticast 01:80:C2:00:00:00 bpdu (vlan 1).

Result:

"(...)Since RSTP only has a single Spanning Tree instance for all VLANs across a trunk and there is no vlan awareness, all traffic will be forwarded or blocked based on the VLAN1 topology."

All good. 

I have now the following case:

--------------------------------------------

cisco switch "distribution" layer  (pvstp)

MAC xxxx.xxxx.3d80, priority 32768

------------------------------------------

                     fa-1/0/8

                          |

                          |

                          trunk

                          |

                      ge-0/0/47

--------------------------------------------

ex switch "access" layer (rstp)

 MAC xxxx.xxxx.8441 , priority 61440

------------------------------------------

Easy:

1)configure vlan 9 on both swicthes

2)I create also the vlan1 on ex side

3)configuration interface on ex-side

set interfaces ge-0/0/47 unit 0 family ethernet-switching port-mode trunk
set interfaces ge-0/0/47 unit 0 family ethernet-switching vlan members 9
set interfaces ge-0/0/47 unit 0 family ethernet-switching native-vlan-id 1

4)configuration interface on cisco sdie

interface FastEthernet1/0/8
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 9
 switchport mode trunk
end

Result

1)ex side

Spanning tree interface parameters for instance 0
Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
ge-0/0/47.0    128:560      128:560  61440.xxxx.xxxx.8441    200000  FWD    DESG

2)cisco side

show spanning-tree vlan 9
VLAN0009
  Spanning tree enabled protocol ieee
  Root ID    Priority    32777
             Address     xxxx.xxxx.3d80
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
  Bridge ID  Priority    32777  (priority 32768 sys-id-ext 9)
             Address   xxxx.xxxx.3d80
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa1/0/8             Desg FWD 19        128.10   P2p

I was expecting to see the cisco as root but as you can see I have basically 2 different root and this is not the wished result.

Any hint here?

Thank you.

Thank you.

Why not just use VSTP config option, set protocols vstp vlan "X" instead?  VSTP was designed by Juniper to allow interoperability with non-standard PVSTP/PVSTP+ from Cisco.  For + you might need both vstp and rstp configured at same time.

Not sure which model EX you are trying this with (always good idea to include both model and SW version), but below is link to newer ELS model discussion of STP Options:

https://www.juniper.net/documentation/en_US/junos/topics/concept/spanning-trees-ex-series-vstp-understanding.html

I am also attaching an old (but good) document regarding 3rd-party interoperability testing between Juniper and Cisco.

Good luck, hope this helps.

Attachment(s)

Cisco_cookbook[1].pdf   15.87 MB 1 version

Thank you for your reply but I want to test and make it working exaclty this combination

RSTP on EX and PSTP+ on cisco.

Only after that I will try different combination.

hw

version

JUNOS Base OS boot [12.3R9.4]

and in any case also in your coockbook the combiation rstp and pvstp+it works just fine.

ok,

I will close the topic and yes to have interoperability PVSTP and Juniper, as in my case, is needed to configure in juniper side the rstp and vstp as per

https://forums.juniper.net/t5/IOS-to-Junos-I2J-Tips/VSTP-PVST-Spanning-Tree/td-p/136123

https://kb.juniper.net/InfoCenter/index?page=content&id=KB18291