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May 30th, 2013 08:00
Port Channeling ISLs
Hello,
I have multiple ISL links between my edge and core switches. These links are not channeled together to form one large pipe. Do I really need to channel them? Doesn't the switch balance the load between ISLs anyway?
Thanks.
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dynamox
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May 30th, 2013 08:00
in my experience switch does a pretty good job at balancing the load. Typically your host will be "pinned" to one of the ISLs and if that links goes down your host will notice it because its connection will be "re-pinned" to another ISL. When you use port-channels your host would never experience any disruption in service because port-channel state does not change when member links go up or down.
etaljic81
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May 30th, 2013 09:00
Makes sense. Thanks
dynamox
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May 30th, 2013 09:00
PowerPath will complain, that's what i see when i drop a link on non-portchannel ISL between 9513 and 9124e
dynamox
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May 30th, 2013 09:00
btw Ernes, remember you asked me to test FI and MDS connectivity ..where one option is multiple uplinks and another option port-channeled uplinks. You were correct, when one uplink was dropped, everything got pinned to the only remaining uplink ..but then when second uplink was re-enabled ..hosts remained pinned to the first uplink. They only way to "re-balance" it again was to reboot the box. Long story short, i am now using port-channels between FI and MDS (had to enable f-port channel-trunk on MDS)
etaljic81
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May 30th, 2013 09:00
I was wondering about that and thought you forgot. Thank you!
etaljic81
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May 30th, 2013 09:00
Can you elaborate more on this statement: "....if that links goes down your host will notice it...."
etaljic81
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May 30th, 2013 10:00
I did miss it, thank you! This is definitely a good reason to stick with port-channels.
dynamox
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May 30th, 2013 10:00
you probably missed it when i updated our initial conversion, here it is
FCoE directly connected to UCS FI , uplinks b/w UCS FI and MDS
DanPJ
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May 30th, 2013 11:00
Dynamox,
What happens if the link that the host is pinned to gets flooded? Does the switch use the other link that's has more bandwitdh available? Also, when you said, "reboot the box", you mean the host or the switch?
Thanks.
dynamox
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May 30th, 2013 11:00
honestly Daniel i do not know how MDS handles ISL utilization and when it decides to use one ISL over another.
I meant i rebooted the host, but that was specific to using Cisco UCS fiber interconnect.
DanPJ
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309 Posts
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May 31st, 2013 10:00
Thanks!