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Wireless mesh network question
by Andy Stewart Feb. 16, 2015

Feb. 16, 2015

HI guys, I am planning to setup a wireless mesh network at a ham radio event in June. Each mesh node will consist of two Linksys WRT54GLs, much like the demo I showed at a recent WLUG meeting. One of the WRT54GLs will be on channel 6 and carry mesh network traffic. The other one will be on channel 1 and allow generic wifi devices access to the mesh network. It seems like there would be an interference problem if every node allowed wifi access on channel 1. Should this be 4 different wifi channels? It is possible for a user to be within radio range of multiple of them simultaneously. Thoughts? I've never setup a wireless network before and could use your advice. These mesh nodes will be placed outside in weatherproof enclosures with battery power. Thanks! Andy -- Andy Stewart (KB1OIQ) Founder: Worcester Linux Users' Group Founder: Chelmsford Linux Meetup Group President: PART of Westford, MA (WB1GOF)

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Reminder! Meeting tomorrow! Feb. 12th 2015 at 7pm (Mid-Century Room) rm 331!
by Tim Keller Feb. 11, 2015

Feb. 11, 2015

Hey Everybody, This is just a quick reminder that we're having a meeting tomorrow at 7pm in the Mid-Century Room (rm 331) in the student center. Andy is going to be giving a talk about mesh networking! Afterwards we'll do pizza at Tech! Refreshments will be provided at the meeting as well. Later, Tim. -- I am leery of the allegiances of any politician who refers to their constituents as "consumers".

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sshd_config MaxStartups
by Jamie Guinan Feb. 11, 2015

Feb. 11, 2015

Hi Group! I'm seeking opinions about an sshd feature. I was doing some work on a remote system (I did not set it up) that seemed to be refusing ssh and scp connections randomly. I looked into it, and finally stumbled across this from sshd_config(5), MaxStartups Specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeeds or the LoginGraceTime expires for a connection. The default is 10. Alternatively, random early drop can be enabled by specifying the three colon separated val‐ ues “start:rate:full” (e.g. "10:30:60"). sshd(8) will refuse connection attempts with a probability of “rate/100” (30%) if there are currently “start” (10) unauthenticated connec‐ tions. The probability increases linearly and all connection attempts are refused if the number of unauthenticated connections reaches “full” (60). Indeed, the server had this setting, MaxStartups 10:50:20 This just seems like a terrible option. You can DOS their server just by making 20 connections and leaving them hanging. And it breaks any automated scripts relying on ssh or scp (unless you wrap them in a loop until they succeed, ugh). My guess is that the reasoning behind this feature that it will filter out a number of automated attacks. That seems no better than security-by-obscurity, and I know how some of you feel about that. :) Can you think of any sane reason to enable this feature, or for it to even exist at all? Best regards, -Jamie

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linux networking question (reformatted for readability)
by Brad Feb. 8, 2015

Feb. 8, 2015

(i appologize for the previous message that i completely unreadable.) Dear W-LUGgers, I had some strange network related behavior that left me baffled and i wanted to hear some theories from more experienced network admins. The network layout is the following. The network is pretty simple, external traffic passes through a bridged-firewall (OpenBSD, my choice) into an OS X server (not my choice) which handles NAT/DHCP/DNS et al., and all the office computers are dhcp clients to the OS X server. The trouble machines are linux (ubuntu) desktop clients. The scenario is the following. I was doing work on the bridged firewall (OpenBSD) and somehow caused it to kernel panic, oopsie! So the bridged-firewall went down thus no-one had internet access, Dou! i quickly bounced the machine. It came back on-line and clients were able to access the internet, huzzah! But, the strange behavior was in two linux machines within the network that were not able to access some external IPs. My linux desktop could not access 8.8.8.8, when pinging, i could see an arp who-has request originating from my machine, i could see the packet come into the OS X server. But the request always went unanswered. The same behavior happened to another linux desktop but with 192.48.178.134 (sgi.com) My desktop could ping sgi.com. So each linux desktop had *different* unreachable IPs. The rest of the internet was reachable. I tried clearing the arp-cache on the OS X server, then clearing the NAT state tables, then I rebooted the OS X server, none solved the problem. I finally renewed the dhcp lease on my linux desktop machine and that allowed the ping to complete. What would case this behavior? Could it be stale arp-cache on the linux machine? ( I *should* have tried to clear the arp-cache on the linux machine before i renewed the dhcp lease, but i didn’t think of that until after the fact.) The linux machine was sending out arp who-has requests so would a stale cache even matter? Why would no one answer the arp requests? I am not an expert network admin (its just a side job since the company is only 15 people). I don’t expect to get a resolution but i’m interested to hear any theories. Thanks and cheers, — brad PS. As a worcester transplant to boston, i am really jealous i don’t live closer to attend meetings. The topics of late sound outstanding.

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linux networking question.
by Brad Feb. 7, 2015

Feb. 7, 2015

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Reminder: Next WLUG Meeting will be Thursday February 12th 2015 @ 7pm Rm 331 (Mid-Century Room)
by Tim Keller Feb. 6, 2015

Feb. 6, 2015

Hey Everybody, I'm glad to announce that our founder Andy Stewart will be doing a talk on wireless mesh networking! I expect this talk will be both entertaining and interesting. Afterwards we'll be retiring to Tech for pizza! Date: Thursday February 12th, 2015 7pm-9pm Location: WPI Campus Center, Mid-Century Room 331 Later, Tim. -- I am leery of the allegiances of any politician who refers to their constituents as "consumers".

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Opening, C++/Linux SW Eng, Permanent; Johnston, RI
by Tim Longua Feb. 5, 2015

Feb. 5, 2015

Our Client in Johnston, RI is looking for a Software Engineer to help in the design and development of an exciting next generation platform. This candidate will be working with cutting edge tools and technologies. Requirements Include: * 7 + years C/C++ experience developing commercial products * Experience developing distributed systems and applications on RedHat Linux or Embedded Linux is required * Multithreaded and object oriented design experience * Oracle, MySQL, or other database experience * TCP/IP, Socket Programming, Qt and Hadoop are all plusses If interested please send your resume to timL (at) connectedsp.com. Regards, Tim Longua Connected Systems Partners Connecting Top Talent with Top Companies Office: 978-455-5550 x206 Cell: 603-303-8978 timL(a)connectedsp.com<mailto:jspencer@connectedsp.com> www.connectedsp.com<www.connectedsp.com%20> GET CONNECTED! Unless otherwise explicitly instructed by sender, all information in this email is considered confidential and intended for the view and use of the recipient(s) only.

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??JGAAP.JAR???
by Colin Novick Jan. 27, 2015

Jan. 27, 2015

Anyone here ever use JGAAP, the authorship Java JAR program? http://evllabs.com/jgaap/w/index.php/Main_Page It is returning errors, and sadly, I do not know enough to interpret the terminal lines to figure out why it keeps returning errors when you run the analysis, even if you try it in various ways. The program is clearly running but there is a catch. Anyone out there familiar with this? Thanks guys! Colin

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The speaker for the February meeting has been lined up!
by Tim Keller Jan. 26, 2015

Jan. 26, 2015

Hey Everybody, Great news! Andy will be speaking at the Feb. meeting! He's going to be doing a talk on Mesh networking. I figure this will "mesh" nicely with Frank's talk about 802.11*[nn]* networking. Once I get the official title for the talk I'll send out a more official reminder. On a different note... Is there anything that people are interested in that we could work on lining up speakers for? Here's a couple of ideas... * Software defined networking * Robotics * Home automation -- I am leery of the allegiances of any politician who refers to their constituents as "consumers".

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Reminder: WLUG meeting tomorrow (Jan 8th 2015)
by Tim Keller Jan. 7, 2015

Jan. 7, 2015

Hey Everybody, Just a reminder we've got a meeting tomorrow! Frank Sweetser is going to be giving an impromptu talk about the new 11ac wireless standard. What issues it addresses and likely creates, along with other wireless standards coming over the horizon. Date: Thursday January 8th, 2015 Time: 7pm Location: WPI Mid Century Room (rm 331) We'll be doing the usual refreshments and pizza afterwards. Thanks, Tim. -- I am leery of the allegiances of any politician who refers to their constituents as "consumers".

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