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WAN and VLAN issues July 8, 2009

Posted by jamesisaac in Uncategorized.
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With the arrival of the DSS SANs, the project is moving ahead with great speed. We purchased two SANs from Silicon Mechanics, with the goal of configuring synchronous replication between them. They arrived each in a large box, containing the 2U chassis and a large pink foam insert with each drive packaged up separately. The Silicon Mechanics technicians had loaded the drives, configured the RAID groups, then taken everything apart and packed the drives along with instructions for reassembling everything at the destination site. I assume this improves the reliability by not shipping the storage server with drives installed. They did a very thorough job of protecting everything. The end result is 3.5 TB of fast, SAS-based storage. I’m extremely happy that we are able to use 1TB SAS drives for one of our RAID groups and not have to burn drive slots just to accomodate our larger, but less i/o-intensive vm’s.

I spent a few hours figuring out how to trunk VLANs across the WAN and into the datacenter setup. On the Cisco router side, this involves configuring subinterfaces on the inside and outside interfaces of each router, and setting the “encap dot1q” for each subinterface. It’s an interesting game to play to try to telnet into the appropriate interface and change the ip config of the other interface, so that you don’t cut off the limb that you’re standing on, so to speak. After a few tries I resorted to the console cable and got everything squared away.

The Netgear switches proved to be another mindbender, though, as even though I’ve done this before (and documented it), the VLAN trunking is just not intuitive for someone with a Cisco background. The other troublesome part of the equation is that some devices natively understand and inject their own VLAN information (i.e., the VMWare host servers), but others do not and have to have their native VLAN set at the port. In the end, I found it easiest to set the native VLAN for each device to something other than 1 – that way I was certain that if I was reaching a device, it was through the appropriate VLAN.

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