Connecting Cisco switch to Avaya Environment

Patrick McHenry · ‎05-04-2012

Hi,

I'm introducing a Cisco 3750 switch into a Avaya environment for testing/lab. I'm concerned about any STP, VTP problems I might create as I'm going to give a address on the Management VLAN and connect it to a trunk port on a ERS5520 Avaya. I've set the switch to transparent mode and the VTP revision is set to 0. I've checked the STP priority but it doesn't give any - there is no output because it is not connected. I wouldn't be so concerned but, I'm not sure if any config has been on it before.

Also, is there any way for me to see the STP prioroity without having it connected?

Thanks, Pat.

Giuseppe Larosa · ‎05-04-2012

Hello Pat,

VTP is Cisco proprietary so it is not an issue in multi vendor context.

STP default mode is PVST+ (one STP instance per VLAN) that is again Cisco proprietary.It inteoperate with default 802.1D STP on vlan 1.

show spanning-tree vlan 1 should provide the info you need default values for STP is 32768+ vlan# (with extension id for MAC address reduction)

of course if not connected STP is not running.

However you can connect two RJ-45 ports of the new switch between themselves to have one port in STP forwarding state

Hope to help

Giuseppe

Patrick McHenry · ‎05-04-2012

Guiseppe,

Thanks for the response. I connected a cable to two ports on the switch like you said and confirmed it was at the default 32769 for VLAN 1.

With this testing switch, that is in transparent mode, I will be able to create a Management VLAN interface on the Management VLAN, assign it an address, and connect it to an Avaya switch trunk port to my 3750 trunk port(using dot1q) and all should be good? Meaning I should be able to reach it from different VLANs(providing routing exists and I should be able to create VLANs on the 3750 that exist currently on the Avayas and assign ports to these VLANs? Sorry for the long sentences.

Also, what spanning treee should I set my switch to or should I keep it at PVST?

And, by connecting these switches I don't have to worry about a VTP problem as the Avaya won't listen to it anyway?

Thanks, Pat.

Joseph W. Doherty · ‎05-04-2012

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Posting

You might want to use rapid-STP.

If your Cisco switch is set to VTP transparent mode, it shouldn't (itself) generate VTP although it can forward one received. Later Cisco switch IOSs support a new "off" mode for VTP that will stop all VTP on the switch.

Patrick McHenry · ‎05-04-2012

Isn't RSPAN also Cisco proprietary?

Thanks

Joseph W. Doherty · ‎05-04-2012

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Patrick McHenry wrote:

Isn't RSPAN also Cisco proprietary?

Thanks

Great question! 802.1w isn't Cisco proprietary but rapid-pvst is. If the Cisco version and Avaya won't interact, then you might try MSTP (802.1s), if Avaya supports it.

Patrick McHenry · ‎05-04-2012

Will I run into any problems using RPSAN on the Cisco switch? Meaning, will this cause any undesirable behavior on the connected Avaya?

If I am sure there will be no loop will it be safe to connect test switch to production enviroment?

Maybe I will take a non production Avaya switch and connect it to the Cisco - create a loop and see what happens.

Thanks, Pat.

Giuseppe Larosa · ‎05-05-2012

Hello Patrick,

if you refer to Remote Span be aware that it is Cisco proprietary and requires at least two Cisco switches to work.

Also if there are Cisco switches in the middle they need configuration of the remote span vlan-id in order to disable MAC address learning or they could influence the way frames are forwarded on the RSPAN Vlan.

So in your case if you have only one Cisco switch and all other switches are Avaya you cannot use RSPAN but only local SPAN mirroring to another port in the same switch.

MST 802.1s is the most scalable STP protocol if supported on all devices and allows to build multiple topologies. It requires a different approach as you need to provision mapping of all vlans to STP instances in configuration phase.

an MST region requires:

matching MST region name

matching revision number

matching Vlans to STP instances mapping

However, you can map Vlans in the whole range 1-4094 to the STP instances even before creating the vlans in this way you can later pick up a Vlan from a specific range and you know that is served by a specific MST instance = it has the topology of that MST instance (root bridge placement and so on)

Hope to help

Giuseppe

Patrick McHenry · ‎05-06-2012

Sorry Giuseppe, I meant Rapid PVSTP.

Joseph W. Doherty · ‎05-05-2012

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Patrick McHenry wrote:

Will I run into any problems using RPSAN on the Cisco switch? Meaning, will this cause any undesirable behavior on the connected Avaya?

If I am sure there will be no loop will it be safe to connect test switch to production enviroment?

Maybe I will take a non production Avaya switch and connect it to the Cisco - create a loop and see what happens.

Thanks, Pat.

It may cause an issue. I think the most likely would be the two switches wouldn't properly share the same STP topology. Depending whether the two different brand of switches connect with an access or trunk port, one switch or the other might "misunderstand" a BPDU or TCN.

I was just looking at this post: https://supportforums.cisco.com/thread/2136905?referring_site=kapi and Peter writes of uniqueness of Cisco's pvstp (and its variations).

On the Cisco switch you could, I believe, disable STP, and then it should interoperate with your Avaya as would any "dumb" L2 switch that doesn't support STP. This would preclude intentional L2 redundancy between Avaya and Cisco, and would allow physical loops to form on the Cisco, but assuming your Avaya(s) is running STP, it should block a L2 loop to that part of the infrastructure.

What other options you might have to "share" STP between Cisco and Avaya, beyond MST, would also depend on the capabilities of the Avaya (which I know nothing about).

Patrick McHenry · ‎05-06-2012

Thanks, Joseph.

I think I will disable spanning tree on the Cisco and turn on bpduguard on all the ports other than the uplink trunk of the Cisco switch that links to the Avaya so, any possible loops will be stopped at the CIsco switch. That should work till I find the correct inter-operability between the two products.

Thanks, Pat.