3560G -- 24Ts-s (Switch) question

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May 2nd, 2006
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Hi All,


I have a question about 3560G-24Ts-s.


1- How many spantree per vlan supported on the mentioned Switch?


2- If I am running out of the vlan supported by the Switch for example: i have 512 or more vlans has to be created, and need to work per-vlan spantree, how could I solve this issue?


Appreciate any reply,


Thank you,

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ankurbhasin Tue, 05/02/2006 - 01:13
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Hi Friend,


In PVST+ or rapid-PVST+ mode, the switch supports up to 128 spanning-tree instances.


Have a look at this link


http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3560/12225see/scg/swstp.htm#wp1170819


To answer your second question you can opt for MSTP


In MSTP mode, the switch supports up to 65 MST instances. The number of VLANs that can be mapped to a particular MST instance is unlimited


Have a look at this link as how to configure MSTP


http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3560/12225see/scg/swmstp.htm


HTH, if yes please rate the post.


Ankur

Mohamed Sobair Tue, 05/02/2006 - 02:07
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Hi Ankur,


I would like to know, what should I concern about when configuring MSTP Mode?? it gets me confused alittle bit!!! Have u implemented it before?? And is there any restriction that i should concern about? My last point, if numbers of vlans pointed to a single MST is unlimited, then there is no point of using 65 MST cause I can map all my vlans supported on the switch to a single MST!!!


Does the above make sense or not??

Let me know your Thoughts.


I thank u ankur in advance,


ankurbhasin Tue, 05/02/2006 - 02:16
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Hi Friend,


I have never implemented MSTP so cannot give u deep insight about the same.


Yes you can have all vlans in same MSTP instance but then it will bahave like a CST which is common spanning tree instance for all vlans for me which will bring all the disadvantages which you get in CST.


Let Bobby or come Cisco TAC engineer answer this in detail.


Regards,


Ankur

johansens Tue, 05/02/2006 - 03:09
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Hi there,


As Ankur replied, using MST (MIST) brings the concept of CST into the design.. One of the differences which makes MIST better is the ability to have several instances (65 as stated).


The problem with a CST is that all of your VLAN's must behave similar.. that is, you can't block just one and one VLAN off a trunk if you expect to have redundancy intact. In MIST you can consider each instance a separate CST, so you'll have to design your LAN with a maximum of 65 different spreadout's.. This should be enough for your needs...


You should read this document thoroughly *before* you attempt using MISTP:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfc.shtml


Did it help? If so, please rate it.

Mohamed Sobair Tue, 05/02/2006 - 03:28
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Hi guys,


I thank u both for your inputs, it's so helpfull, I just have one last question, what is a CST??


Thank you,

mahmoodmkl Tue, 05/02/2006 - 03:40
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HI


CST means common spanning tree.it is ieee implementation.in CST u have a single instance of STP for all u r VLANS unlike PVST which has a seprate instance for evry VLAN.


Thanks

Mahmood

Mohamed Sobair Tue, 05/02/2006 - 04:56
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Hi Mahmood,


Thanks for ur input, its quite helpful.

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