NPV - what happens when a server is rebooted

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Dec 12th, 2008
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I am using NPV and I was wondering what happens when a server reboots. I have created four external interfaces to the NPIV core switch. I so far have not setup traffic mapping so its free for all as such.

If one server uses fc1/1 when it first uses the switch, what happens when it reboots. Will the switch randomly assign it to the least worked external interface or will it somehow remember it was using fc1/1?


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Michael Brown Fri, 12/12/2008 - 11:39
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Each login (and re-login) is processed and a round robin load balance scheme is applied. So the answer to your question, will it no. It could still land on the same uplink if the round robin-loadbalnce is such that it is the next link in the mix. The links are not really assigned based on current load. If you have 4, and they come up in the order of, the first host will use 1, the second host will use 2 and so on. In a future release of MDS software, the capability of the links between NPV and NPIV switch will be such that they can be combined into a port-channel, and even trunk multiple VSANs. Currently, they can not be a port-channel or carry more than 1 VSAN.

Hope this helps,


stephen2615 Fri, 12/12/2008 - 14:19
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Hi Mike,

Thats very interesting. I somehow thought it was load balanced.


Before Cisco MDS SAN-OS release 3.3(1a), NPV supported automatic selection of external links. When a server interface is brought up, an external interface with the minimum load is selected from the available links. There is no manual selection on the server interfaces using the external links. Also, when a new external interface was brought up, the existing load was not distributed automatically to the newly available external interface. This newly brought up interface is used only by the server interfaces that come up after this interface.

I read pre 3.3(1a) but never really considered it. I hate reading stuff on a computer.. No attention span..

I need to consider traffic mapping for some of our heavy working servers to protect their bandwidth.



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