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Can ping SAN from switch, but not from host

Posted on 2011-09-19
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Last Modified: 2012-05-12
We have Dell Poweredge Windows Server 2008 R2 servers. They are connected to a Brocade/Foundry switch. Attached to the same switch in the same VLAN/Subnet is a Dell Equallogic SAN array.

Every day at seemingly random times, for periods of a few hours, our servers can no longer ping the SAN which is on the same switch. However if I telnet to the switch I can ping the SAN. One might think the switch is blocking them, but yet the SAN volumes are up and data is being written to them, so I know the switch isn't blocking them. We've tried rebooting the SAN, upgrading to the latest firmware, etc. We haven't replaced all of the cables (which are a couple months old), nor have we changed all 4 ports the cables are plugged into. It just seems very unlikely that all 4 of cables or ports that happen to be for a single member would die. We are working with Dell from the SAN and server perspective, but I'm trying to think of anything on the switch that could be the cause. We cannot really reboot the switch as it serves up many other connections/devices besides this SAN.
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Question by:MrVault
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Soulja earned 2000 total points
ID: 36560713
I don't think it is anything on the switch, unless your switch is layer 3 and you have some ACL applied. I would check the cables, make sure you are using a high quality cable. I remember at one time replacing every cable to a SAN because the cables were of low quality. Interfaces kept dropping randomly. We put in high quality cables and never had another problem.
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Author Comment

by:MrVault
ID: 36560939
how do I tell if spanning tree is getting in the way?

here's what's weird. there are 2 enclosures (members) in the SAN group. they share a single group IP and each of the 4 NICs in each member has an IP. At first the 4 in member1 were not pingable except if I was directly on the switch. I unplugged those 4 cables and put them in  4 different ports on the same switch and then they all came up, but 2 on the other member went down. for the last hour those original 4 that were down are up, and 2 new ones are down. these cables are the same type/brand/order as all the others in our network that have never had this problem in 2 years. the cables from all 8 are about 3 months old.

the SAN vendor is thinking it's a switch problem. What's weird is that if you telnet to the switch it can ping all 8. However if you go to a host on the same VLAN plugged into the same switch, that host cannot ping those 2. However if you telnet to another SAN array plugged in 5 switches away, that CAN ping all 8 ports. So we know the switch isn't completely blocking it and the cables are working.
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LVL 26

Expert Comment

by:Soulja
ID: 36561025
I'm not familiar with the Brocade switches, but can you look at the status of the ports in spanning tree and see if they are in blocking state when this occurs?
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LVL 26

Assisted Solution

by:Soulja
Soulja earned 2000 total points
ID: 36561037
Being that you have muliple ports plugging into the switch from the same host, it could possibly be a spanning tree issue.
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Author Comment

by:MrVault
ID: 36561271
they are forwarding always.
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Author Comment

by:MrVault
ID: 36561288
the 4 NICs on the array each have their own IP and there is nothing else on the network with the same IP.
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LVL 26

Expert Comment

by:Soulja
ID: 36561327
It's not a spanning tree issue if they are remaining in forwarding state.
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Author Comment

by:MrVault
ID: 36561837
yeah, that's what we were thinking.

so the other 2 that started having the issue after I updated the others, I've moved those 2 cables into two other free ports on the switch and they are now connecting just fine. we'll have to see if these stay up now. i'll let you know.
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Assisted Solution

by:MrVault
MrVault earned 0 total points
ID: 37019437
we had about 10 more start having the same problem. we replaced the switch (it was an ebay refurb) and so far no issues. bad hardware is likely.
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Author Closing Comment

by:MrVault
ID: 37049221
was hardware issue. could have been a firmware issue, but was not able to get update service to latest code. replaced switch.
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