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Community Member

MSTP participation

Hello

I need  some advices please send me your feeds..

I have MSTP mesh topology and and I want to izolate  two switches which connects to provider side I mean when MSTP calculating I don't want it dissconect or reset links that connected to ISP side because I have connection which must not being interrupted.

So here is  topoloy pic

Could someone tell me how can I izolate two switches which in ISP side and another that connected to  ISP side switch

Thanks

8 REPLIES

Re: MSTP participation

Hi,

You can use 2 MSTP's regions etc but some more information of what exactly you are trying to do would be good? When you say isolate Are you saying that the switches should not talk to each other ? What are you using the interconnect trunk link between the local switches for?

HTH

Kishore

Community Member

Re: MSTP participation

Hi,

I don't want  disturb that switches  which interconnect ISPs I have lots of  switches in my local and when making changes it start calculating   then it reset conectivity  thats why  I  want to exclude that switches from being calculating or participating in MSTP process   by the  way I use VTPversion 3 with MSTP

and  what do you think will  mstp  new region help me or I should try smth else?

because  only two  switches I want to  not participating

I have configured Ipsec HA to multiple ISPs for important services it Happend twice when adding new switch or instance to MSTP it resets conectivity

Thanks

Agha

MSTP participation

Hi ,

I will get one of the experts to see if he can help you with this.

HTH

Cisco Employee

MSTP participation

Hello,

A couple of questions:

  1. Why do you actually run STP towards your ISP? Is that necessary?
  2. How many physical links are connecting your network to the ISP? Is it just a single physical link, or are there multiple physical links (assuming no EtherChannel configured)?
  3. Are you using 802.1Q VLANs on the connection towards your ISP, or is there only a single VLAN transported? Is it tagged or untagged?

Best regards,

Peter

Community Member

MSTP participation

Hi Peter

I don't run stp to my ISP  I just bundled all my switches in one MSTP

Switch which directly connected to ISP have lots of vlans and  switch which connected to that switch  via optical link

I use both tagged and untagged

My point is how it's  possibly to izolate  these two switches from the rest in my mstp region?

or If I remove them from mstp will it work good with mstp not participating in mstp calculation?

Thanks

MSTP participation

Are these links that you run toward your ISP L2 or L3?

Cisco Employee

MSTP participation

Hi Agha,

Now I understand better - at least I believe. You may be experiencing outages caused by MSTP Proposal/Agreement mechanism propagating from the point of a topological change down to your links with ISP, but with nobody to answer the Proposal from the ISP with an Agreement, these links remain blocked for 30 seconds after certain topological changes.

A possible solution would be to use the command spanning-tree portfast trunk on the interface that is the closest to your ISP and connects your network to the ISP. This will forcibly declare the port as an edge port that is not influenced by Proposal/Agreement processes.

Another spanning-tree portfast default global level configuration command should also be used on all your switches in your network to make sure that access ports are treated as edge ports (ports connected to end devices rather than other switches) and hence are also not influenced by topological changes.

Would you be willing to test this configuation?

Best regards,

Peter

Community Member

MSTP participation

Hi Peter

I'll check it and let you all know

Thanks,

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