VSP7000 IST & VLACP

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According to varying design docs / best practice it is recommended to disable VLACP on IST links of a VSP7000 cluster. However, I cannot find anywhere that says why. Anyone know?
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Marc Daley

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Posted 4 months ago

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Roger Lapuh, Employee

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There are a couple reasons:a) VLACP is a link based protocol, vIST can use any NNI link that is up, so VLACP does not really make sense.b) we only want the vIST session to go down when the peer switch is really down, thus we have pretty long timers, in case there are some intermittent failures, VLACP would interfere with those timers. When vIST session goes down, then vIST nodes convert their SMLT ports to normal ports, thus intermittent IST link down events would increase the risk for loops.I hope this helps, Roger
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Marc Daley

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That's great, thanks for the detailed response. In the case of running traditional IST with SMLT I assume only b) in your answer applies? A colleague also mentioned that there may be some ASIC restriction with the 7ks?
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Roger Lapuh, Employee

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yes, for IST deployments b) applies. I am not aware of any ASIC restrictions on the VSP7200 that would trigger not to use VLACP with IST/vIST. Keep in mind, if you are running the VOSS switch in non-SPB mode, the switch is still using vIST concept internally, even though you are configuring it as normal IST/SMLT, but this does not have any consequences for VLACP.
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Marc Daley

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Thanks again but just to be clear, I'm talking about the VSP7000 not VSP7200. From what I understand it's architecture differs significantly from the later VSP7200 range.
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Roger Lapuh, Employee

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Marc, yes, I was assuming VSP7200. HW and SW IST implementation are quite different between the two products. ERS switches are typically a bit more sensitive to short VLACP timers, especially when stacked. The VSP7000 was using the ERS operating system (BOSS), it is EOS since quite a while now.
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Marc Daley

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Thanks roger, appreciate the clarification.