As long as there have been wireless networks there have been people trying to squeeze out just a bit more range… there was the cantenna and now there are other variations on trying to collect and improve the amount of signal getting to wireless adapters… here is just a sampling of what I’ve looked at (and expiremented with) lately… instructables how-to using seive… and another page along the same lines and for wireless hardware that is a bit more powerful… Keenan Systems sells engenius/senao wireless products that tend to have higher sensitivity/power output than the average linksys/dlink.
Category: Networking
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Yet another domain tools site.
For a while dnsstuff.com has been my favorite dns tools web site, but there are others. Recently I was pointed to domaintools.com.
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Emailing large files….
There are lot’s of ways to get a file from one place to another, emailing is the first that many think of. (For larger files I’ll usually just upload to a directory on the website and then email a link…) The problem with email is multiple…. 1)viruses exploit email as a delivery vehicle and so attachments are looked at with rightful suspicion…. and 2) the size of emails is usually capped SOMEWHERE along the way, my isp, your isp, etc…. Usually that cap is around 5-10MB There are other ways to get a big file from point a to point b – (don’t underestimate the bandwidth of the postal service and dvd-r’s….) One online alternative though is yousendit.com – you upload a file, tell who you want it sent to and it appears that they send a link via email so the recipient can download.
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Zeroshell Livecd – providing main network services
http://www.zeroshell.net/eng/ is an interesting bundle of linux designed to be an out of the box network service swiss army knife of sorts. Here are the network services that it provides…. Kerberos 5 authentication, LDAP, NIS, Radius authentication, x509 certificate authority, unix and windows compatible active directory services, router, implements bridging and vlan protocols, full radius server, captive portal capability, firewall, QoS management, multizone dns server, dhcp server (capable of managing multiple subnets), ntp server, dyndns client, ppoe client, syslog server, lan to lan vpn…..
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Handy DNS tools online
There are some tools that I make use of almost daily. Either because something strikes my curiousity or because of necessity to find out a bit more about a computer issue. DNS lookup tools fall into the category of “must have” for the kind of stuff I wind up doing. Whether it’s a whois lookup to see who is a contact for a given domain, looking to see when a domain expires or just looking up reverse dns information to find out where the machine is located that’s been trying to enter the ssh server. Of course, spam blacklist lookups are handy too. I’m adding a few links to the sidebar for some of the more useful of these…
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Offline web browsing script
In the US and Europe and many more developed parts of the world we take our internet connectivity these days for granted. (And some go into panic attacks when it’s not available…) In some parts of the world though internet connections are not as wide/broad and peak usage times can make for very slow viewing, or can interfere with other vital communications. Linux excels at SO many things and this is something we could use linux to help with…
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UDP problem…
I found a peculiar problem while I was setting up an openvpn link the other day. The goal was a simple shared key setup and I started with the sample configuration and modified it a bit to fit the circumstances, I allowed the correct UDP port through the firewall (I think 1194 if I recall correctly) and … it didn’t work. So…. I started over and worked from empty config files and put in the bare minimums… it still didn’t work – no appearance that it was making the connection at all to negotiate the link. I double and triple checked the firewall config/restarted it… nothing Then I decided to try TCP instead of a UDP port. Changed the firewall config to allow the TCP traffic on 1194, adjusted the server and client config and lo and behold it worked. The firewall in question….
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Blacklists and rejecting mail with Sendmail
A long time ago I had found how easy it was to reject messages outright with Postfix that came from non-existent domains. You know… junk from asdflkjuasdlfkjh@imadethisupmyselfanditsnotregisteredanywhere.com
Well, since the mailserver at THIS site runs sendmail I wanted to fix sendmail the same as my home server. My home server is postfix based and uses fetchmail to pull from the website. Since I had the rules set to reject non-existent domains at home it would essentially strand messages in the account here at the website which would then need to be cleaned out manually.
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More postfix spam blocking and Whitelisting….
I almost forgot to pass along a link to a more comprehensive detailing of postfix’s anti-uce controls…. here. Also, in the last article I briefly mentioned whitelisting. IF you intend to have several blacklists active it will pay to learn how to whitelist before you HAVE to. To do so, I simply created a text file at /etc/postfix/whitelist and int hat file you enter IP address or hostname followed by OK…. like this….
1.2.3.4 OK
goodmachine.com OKBut… of course, there’s a bit more.
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iScsi and AoE with linux
A few days ago I had reason to investigate iscsi and AoE (ata over ethernet). Both are protocols for sharing a physical drive over the network at the block level. Let me put it in context first. Traditional network file shares have been done like this…. Computer A has a large drive, it’s formatted and available to Computer A and then THAT computer shares it out to computers B-zzzzzzz. iscsi and AoE basically share the bare drive and then computer B can attach to the drive format and make use of it as it’s own. Realistically I see the greatest advantage with this is adding storage to a server.