sam's questions

Ive got a smart PDU (Pakedge) which pings, various LAN devices in the rack and if they dont respond it power cycles the associated power outlet to reboot the device, it also sends me an email alert.

What safe guards can i put in place to stop false positives coming up where for instnace the network switch is powered down and then every device would "look offline" / frozen to the PDU ?

UPDATE Some answers have correctly mentioned that force power cycling devices in the above manor could cause issues, i should clarify the device that im doing this to in this above instance are rack mounted AV matrixes / amplifiers rather than servers / NAS

Is it possible to isolate a network device from the rest of the LAN via its MAC address ?

Im familiar with creating a VLAN based on a tagged port of the network switch, but is it possible by recognising the devices MAC address ?

Im speccing up a new 16A PDU for a 42u rack build, i need a PDU with IP control so that i can power cycle devices remotely. But I've noticed that most PDUs with IP control don't have surge protection on them.

I can find lots of surge protected PDUs but they tend to be "rack mounted surge protected extension leads" rather than IP controllable PDUs.

Any idea why this is ?

My thought was that i could get a IEC PDU, IP, but non surge and then plug some IEC surge protected "rack mounted extension lead type PDU" something like THIS. But if i did that although the equipment in the rack would be surge protected, the IP controllable PDU wouldn't be.

I'm managing an office network which is spread across 2 buildings. (see network setup below)

In building 2, we are getting a problem where the network slows down and then completely cuts off. The only way to bring it back is to power cycle the switch, then before it slows down again, go into the GUI dashboard and power cycle it from the dashboard.

The issue has happened 4 times (and is becoming more frequent). It first happened 2 weeks ago, then again yesterday, and twice today.

I'm trying to work out what could be causing it. I've believe I've narrowed it down the switch as the only network devices in building 2 are the switch and the WiFi access point. When the switch is down, the WiFi access point is still running.

When building 2 is down, if i go to building 1, I can still connect to the network fine.

Any idea what might be causing the above? My 2 guesses are:

1. network storm - but this would be odd as we haven't recently added notable new devices to the network. So why has it come about all of a sudden, plus why is it getting worse on each reset?

2. faulty switch (needs replacing under warranty)

Network is configured as follows :

Building 1

• Draytek 2860 router (connected to fibre modem)
• Netgear 24 gigabit port smart switch
• Ubiquity UAP wifi access point (mostly used by mobiles / tablets.. low traffic)
• 4 wired LAN computers (heavier use, as we all use dropbox on LAN sync mode for heavy files)
• printers and other devices
• all cabling cat6

Building 2 (connected to building 1 by cat6 c. 30m cable length)

• Netgear 48 gigabit port smart switch (Netgear GS748T)
• Ubiquity UAP wifi access point (used mostly by 2 laptops, heavier usage that building 1, again most traffic is used from dropbox LAN sync.)

Ive just migrated quite a few sites to new server. In doing this i also have done a audit of the DNS setup of all our domains.

Several domains use Google Apps for their email and i noticed a couple of discrepancies in the MX records they used (please see full list of MX records below). Domain L, starts with 0 - APSMX, where as the others start with 10 - ASPMX. Non of them are identical after the first record either.

Are any of these right / wrong ?

Could there be an issue with mail not getting through due to the way they are configured ?

Domain L

0 - ASPMX.L.GOOGLE.COM
5 - ALT1.ASPMX.L.GOOGLE.COM
5 - ALT2.ASPMX.L.GOOGLE.COM
10 - ASPMX2.GOOGLEMAIL.COM
10 - ASPMX3.GOOGLEMAIL.COM

Domain PP

10 - ASPMX.L.GOOGLE.COM
20 - ALT1.ASPMX.L.GOOGLE.COM
20 - ALT2.ASPMX.L.GOOGLE.COM
30 - ASPMX2.GOOGLEMAIL.COM
30 - ASPMX3.GOOGLEMAIL.COM

Domain P

10 - ASPMX.L.GOOGLE.COM
20 - ALT1.ASPMX.L.GOOGLE.COM
20 - ALT2.ASPMX.L.GOOGLE.COM
30 - ASPMX3.GOOGLEMAIL.COM
30 - ASPMX2.GOOGLEMAIL.COM

I've got a local network rack with:

• 24 port switch
• 2x voip dect bases
• 2x modems
• 1x load balancing router
• 1x wifi access point
• 1x 2bay Synology nas

At the moment these are all powered via 2x 1U 6 socket surge protected PDUs.

I want to add a UPS into the rack but the ones I was looking at in terms of power / battery output only have 4 power ports on the back. Can I plug the PDUs into the UPS to get around that or would that cause an issue?

The reason I ask is because I've heard that if you daisy chain 2 surge protected extension cords you negate the surge protection, so I was wondering if I plugged the PDU into the UPS if it would have a similar effect?

Ive got a technicolour tg582n pro router that ive disabled SIP ALG on (as per my voip providers request).

To do this on this model of router i followed this guide online where you telnet into the router run a command (although it has a browser based dashboard SIP ALG isn't accessable from there), i believe I've disabled it correctly as i didn't get any error message up when doing it, but cant be 100% sure.

Is there a test i can do to check is SIP ALG is disabled on my router ? Ive found some online Java applets that seem to test this but when ever i click to use them they all need complete access to the computer to run, which im not happy doing as i have know idea who these sites are. Is there another way it can be tested either through a telnet query or somthing similar ?

To maximize convection cooling in a rack, does it make a difference whether the hottest items are at the top or bottom? If so, which produces the most cooling and why? Please limit answers to ones based on facts or industry-standard design principles rather than speculation, opinion, or personal choice.

Please note for this question I want to focus purely on the effect of the placement of the items on convection-only cooling. Please ignore other considerations, such as weight distribution or use of fans.

Recently we've had several attempts to access our ftp account from an outside source, (we've since locked the account).

I was wandering if we use hosted webmail, such a open xchange, horde or atmail would our email db's be venerable / accessable if someone was able to get onto our server, via ftp or otherwise ?

Correct me if im wrong but the hosted webmail services ive listed above are normal lamp (or similar) web apps ?

I want to set up mod_proxy to work so that my blog is running under a subdirectory of my site rather than subdomain so i get the seo backlink benefit.

What im looking to do is get my tumblr blog which is running at blog.mysite.com (which is in turn mapped from myblog.tumblr.com) will be running on mysite.com/blog

How can i set up mod_proxy to do this, is it just something that i can setup from inside of my .htacess file ?

Ive got my site hosted on an apache server, using plesk as a controll panel.

I contacted my webhost and they told me mod_rewrite could acheve it, they gave me this but said they wont provide me further support regarding mod_rewrite as its somthing they dont support

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_HOST} ^example.co.uk/blog$
RewriteCond %{REQUEST_URI} !/standard
RewriteRule ^(.*)$ http://example.tumblr.com$1   [R]
</IfModule> 

ideally id like to use the mod_proxy method as it recomended from an seo point of view from this article http://www.seomoz.org/blog/what-is-a-reverse-proxy-and-how-can-it-help-my-seo