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  • Question

  • Since a single VLAN is by definition a single point of failure why do you use them in your site resiliency design between sites?
    Wednesday, August 5, 2009 9:05 AM

Answers

  • You have a good point those things could affect it but then agin those things could affect any network not just a spanned VLAN. I am not sure you are increasing your risk when the latency is only allowed to be 15ms which mean either metro ethernet or some other high bandwidth link between your redundant sites. I think you need to take into account the whole story here. I am not saying this is a great design but the VLAN is really the least of the possible problems with this architecture.

    Cheers
    Chris
    http://voipnorm.blogspot.com/
    Thursday, August 6, 2009 3:37 AM

All replies


  • On a related topic, Microsoft has recently released a white paper entitled "Microsoft Office Communications Server 2007 R2 Site Resiliency White Paper" which you may wish to check out.

    Hope this helps. Please do let us know. thanks.


    TechNet Forum Moderator - http://www.leedesmond.com
    Wednesday, August 5, 2009 9:25 AM
    Moderator
  • Hi,
       That's the paper I'm reading, in it on page 5 you have what appears to be ALL servers connected to a single VLAN (Net 1) over two sites...

    Cheers

    Ian

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    Wednesday, August 5, 2009 9:51 AM
  • so back to the original question then:

    Since a single VLAN is by definition a single point of failure why do you use them in your site resiliency design between sites?


    Wednesday, August 5, 2009 11:13 AM
  • From the document

    " The two internal HLBs were configured as a redundant pair and were in constant communication with each other. The internal HLB on one site acted as the primary HLB, exposing the VIP for internal resources (anything connected to the internal network) on both sites. If the primary HLB were to go offline, the secondary HLB would take over and respond with the same VIP (same FQDN and IP address). This is possible because all internal resources in two separate sites were part of the same stretched VLAN in the same IP subnet." Pg 7.

    This is you answer. The only way to get the HLB to respond with the same IP address is to have the subnet spread over the two sites. Things like HSRP and other protocols can make it so VLAN isnt a single point of failure.

    http://voipnorm.blogspot.com/
    Wednesday, August 5, 2009 2:09 PM

  • So a flapping spanning tree or high volumes of broadcast won't impact every device?
    Wednesday, August 5, 2009 3:24 PM
  • You have a good point those things could affect it but then agin those things could affect any network not just a spanned VLAN. I am not sure you are increasing your risk when the latency is only allowed to be 15ms which mean either metro ethernet or some other high bandwidth link between your redundant sites. I think you need to take into account the whole story here. I am not saying this is a great design but the VLAN is really the least of the possible problems with this architecture.

    Cheers
    Chris
    http://voipnorm.blogspot.com/
    Thursday, August 6, 2009 3:37 AM