Hashemian Blog Web Tools, Financial Markets, Technology Monday, December 24, 2007 ARP, arping, and MAC  Sometimes one could become so comfortable with something, that one becomes blind to the underlying technology. Such was the case with me a few days ago when I was trying to delete an IP address from one Linux node on the network and assign it to another. The problem was that the new node would remain inaccessible on the network. It would eventually show up, but that didn't make troubleshooting easy. We're all so used to plugging a node into a switch and have it up and running that we forget that underneath the IP address, there's the MAC address with the DNS-like ARP tables running on switches and nodes. Apparently the "service network reload" command on the Linux box wasn't making any ARP announcements on the network, leaving the ARP tables (evidently with long aging timers) with old mappings. And that explains why the new Linux node would remain inaccessible for some time. I'm not sure if the network subsystem in Linux is supposed to advertise a new IP to MAC (possibly using a an ARP request). Strangely, even a reboot wouldn't fix this problem. It is possible that the firewall (iptables) rules were preventing this. Whatever the case, a manual ARP request using the arping command seemed to have resolved this. Here's the syntax (with a phony IP): arping -U -I eth0 192.168.100.100 arping is a useful Linux tool similar to the ping command, but operating at the MAC level. I suppose there's a good chance that even pinging a node on the local network from the Linux box would have done the trick and updated the ARP tables. Anyways, if you find yourself in a similar situation, check the ARP tables on your switches. They're so easy to forget. linux,arp,mac address,ethernet,ip address,network switch Labels: computers, networks <ARP, arping, and MAC> // posted by rh 0 comments Wednesday, December 12, 2007 Google Lifeblood  Like most people who have a Web site I check my site's ranking on Google SERPs (Search Engine Results Pages) from time to time. It's striking how much of a Website's life depends on Google. That's particularly true with smaller sites whose lifeblood is the traffic Google sends their way. But even bigger sites would suffer severely if their pages suddenly lost ranking in Google. Sure there are other search engines like Yahoo and MSN, but enough about those. And so when a couple of days ago I noticed that my site's traffic had a noticeable drop in traffic, the first place I looked for diagnosis was Google. Sure enough, my site's pages where either non-existent or had dropped considerably in ranking. I know that compared to other sites, my traffic is but a drop in a proverbial bucket, but even so the realization of lost ranking made me concerned. I can only imagine how those people, whose living is tied to their traffic, may feel when Google starts to snub their sites. the results could be devastating. Had I violated any one of Google's quality guidelines? Had I engaged in any activity that might have blacklisted my site? I was stumped. I hadn't made any design changes to the site that I could recall. I even tested my site for unintended search engine spamming using a couple of different online tools. One claimed I had hidden text on my pages. They were light-colored timestamps on a colored background. Just for insurance I changed them to a darker color. It also caught what it regarded as keyword stuffing. The culprit turned out to be whitespace characters (&nbsp;) with missing trailing semi-colons. So at least I got to fix this error on my site, and then I just moved on. Today, inexplicably my site's ranking in Google SERPs seems to be back where it used to be. Could this have been the result of those minor changes? I don't think so. Most likely, the drop was due to some temporary event in Google's algorithm. What's alarming is that Google is not just influential, but it's vital to so many. Where can one go to if they are unfairly treated? Who will listen? This is not a paid service, there are no SLAs (Service Level Agreements), contracts, or even tenuous promises. Mine is just a hobby site. Being present in Google is great, but I'd still be doing this even if my site wasn't included. I don't think my attitude would be the same if I were making a living off my site. I can appreciate that Google has the enormous task of separating the good sites from the bad. But with that much power and reach, it is inevitable that many innocent sites will be inadvertently punished. Consider how things would be if there were only one powerful and unregulated credit agency with two marginal ones, instead of the three with equal standings today. google,search engines,seo,serp,spam,page ranking Labels: google, seo, spam, web <Google Lifeblood> // posted by rh 0 comments Tuesday, December 04, 2007 High-Tech Sales Pitches  So today I'm at my desk in the office fiddling with a new Web accelerator toy, er appliance, and I get the dreaded call transfer from the front desk. The Web caching box must've had fried my common sense and I took the call. It was a sales pitch. People who call my number at the office usually dial my extension directly. Even then, they get a call-screening message asking them to identify themselves. If I am at my desk and if it's urgent, I pick up the call, otherwise they go into the voicemail and I get back to them later. Generally, the only times calls are transferred to my extension via the front desk are when someone calls up the office and asks for the Web guy or the programmer or the developer and those are typically salespeople pushing a new and exciting product or a service or the survey guys asking for 5 minutes that last a good half hour. The sales guy was peddling Microsoft and Cisco training courses. With my mind still on Web caching, I half-heartedly listened to the man drone on effusively about their courses and their various membership levels. He had me browse to their Web site and took me through some of their marketing pages. Not wanting to be discourteous, I obliged, but he must've realized that I wasn't exactly the type of ready and willing customer he was hoping for. Undaunted, he pushed on buttering me up with compliments that I was a part of an exclusive group chosen to receive the course material at a substantial discount. I finally had to cut him off and asked the inevitable question, "How much?" Sensing slippage, he promptly handed the call over to one of their professional and cheerful salespeople with the hopes that the new guy would close the deal. When I resisted, the cheers suddenly gave way to a quick thank-you and a phone number to call back and that was the end of it. I don't understand this. I mean I know techies are eccentric and lack some social skills, but are we taken for easy prey? I could almost hear the salesman's thoughts through all the pleasantries, "Buy it, you dumb ass. Take the bait. Buy the stupid course." I suppose there are some of us out there who would succumb to the art of persuasion. I've had my weak moments too, but not today. If only he was peddling a Web caching courseware today. sales pitch,telemarketing,web caching,web accelerator Labels: customer service, sales <High-Tech Sales Pitches> // posted by rh 0 comments

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