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Re: [Wlug] linux networking question (reformatted for readability)

by Brad

On Sat, Feb 07, 2015 at 04:40:36PM -0500, Frank Sweetser wrote: > This is just a rough guess, but did you ever check on the state tables > in your openbsd firewall? > I did not check the state tables in the OpenBSD firewall. I figured since it had just been forcefully reboot the state tables were coherent. > In your setup you have state distributed > amongst your clients, your firewall, and you NAT gateway, and unless > all three are in sync you can easily get the kind of possessed network > behavior you describe. > To properly exorcize should i pour holy-water over the routers? I always figured some king of black magic was involved in routing. Is a bridged-firewall not a good idea in practice because it adds another layer between the internat and the intranet, and could get out of sync? Thanks for the ideas, - brad > On February 7, 2015 3:20:15 PM EST, Brad <bkn(a)ithryn.net> wrote: > >(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. > > > >_______________________________________________ > >Wlug mailing list > >Wlug(a)mail.wlug.org > >http://mail.wlug.org/mailman/listinfo/wlug > > -- > Sent from my Android device with K-9 Mail. Please excuse my brevity.

Feb. 7, 2015

Re: [Wlug] linux networking question (reformatted for readability)

by Frank Sweetser

This is just a rough guess, but did you ever check on the state tables in your openbsd firewall? In your setup you have state distributed amongst your clients, your firewall, and you NAT gateway, and unless all three are in sync you can easily get the kind of possessed network behavior you describe. On February 7, 2015 3:20:15 PM EST, Brad <bkn(a)ithryn.net> wrote: >(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. > >_______________________________________________ >Wlug mailing list >Wlug(a)mail.wlug.org >http://mail.wlug.org/mailman/listinfo/wlug -- Sent from my Android device with K-9 Mail. Please excuse my brevity.

Feb. 7, 2015

linux networking question (reformatted for readability)

by Brad

(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.

Feb. 7, 2015

linux networking question.

by Brad

Feb. 7, 2015

Re: [Wlug] Reminder: Next WLUG Meeting will be Thursday February 12th 2015 @ 7pm Rm 331 (Mid-Century Room)

by Andy Stewart

On 02/05/2015 10:29 AM, Tim Keller wrote: > 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. HI WLUG, Thanks, Tim, for sending that notice to the WLUG membership. Specifically, I will be discussing Broadband-Hamnet (trademark), which is a mesh network designed by amateur radio operators, but can be used by mere mortals :-) as well. One can reflash many versions of the the Linksys WRT54G with this software and create your own mesh network, as has been done in Austin, TX and I believe Seattle, WA. Also, the Ubiquiti hardware can be used. I will have slides and a few Linksys boxes to demonstrate the concept. Feel free to bring your laptop to connect to the demo network. One can connect via an ethernet cable (bring your own) or wirelessly. For more information: http://www.broadband-hamnet.org I look forward to seeing you at the meeting, and joining you afterwards for pizza. Andy -- Andy Stewart (KB1OIQ) Founder: Worcester Linux Users' Group Founder: Chelmsford Linux Meetup Group President: PART of Westford, MA (WB1GOF)

Feb. 6, 2015

Opening, C++/Linux SW Eng, Permanent; Johnston, RI

by Tim Longua

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.

Feb. 5, 2015

Reminder: Next WLUG Meeting will be Thursday February 12th 2015 @ 7pm Rm 331 (Mid-Century Room)

by Tim Keller

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".

Feb. 5, 2015

??JGAAP.JAR???

by Colin Novick

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

Jan. 27, 2015

Re: [Wlug] The speaker for the February meeting has been lined up!

by Tim Keller

For the holidays I setup my raspberry pi to act as an automatic christmas tree waterier. Thus I've become quite acquainted with the GPIO (General Purpose I/O) pins on the raspberry pi. I could definitely give a talk that would be a primer on controlling TTL devices using a raspberry pi and python. On Mon, Jan 26, 2015 at 2:45 PM, David Glaser <dglaser(a)glaserresearch.net> wrote: > Regarding SDN, the following link is rather interesting. > > > http://www.att.com/Common/about_us/pdf/AT&T%20Domain%202.0%20Vision%20White… > > -David > > On 01/26/2015 12:49 PM, Frank Sweetser wrote: > > I've been watching the whole software defined network mania fairly > closely, > > and while I honestly don't even know what a presentation about it would > look > > like, I'd always be happy to just chat for a while about if it there's > > interest. (One little teaser - a good segment of it involves running > Linux > > directly on enterprise class network gear!) > > > > Frank Sweetser fs at wpi.edu | For every problem, there is a > solution that > > Manager of Network Operations | is simple, elegant, and wrong. > > Worcester Polytechnic Institute | - HL Mencken > > > > On 01/21/2015 10:43 AM, Tim Keller wrote: > >> 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". > >> > >> > >> _______________________________________________ > >> Wlug mailing list > >> Wlug(a)mail.wlug.org > >> http://mail.wlug.org/mailman/listinfo/wlug > >> > > _______________________________________________ > > Wlug mailing list > > Wlug(a)mail.wlug.org > > http://mail.wlug.org/mailman/listinfo/wlug > > > > _______________________________________________ > Wlug mailing list > Wlug(a)mail.wlug.org > http://mail.wlug.org/mailman/listinfo/wlug > -- I am leery of the allegiances of any politician who refers to their constituents as "consumers".

Jan. 26, 2015

Re: [Wlug] The speaker for the February meeting has been lined up!

by David Glaser

Regarding SDN, the following link is rather interesting. http://www.att.com/Common/about_us/pdf/AT&T%20Domain%202.0%20Vision%20White… -David On 01/26/2015 12:49 PM, Frank Sweetser wrote: > I've been watching the whole software defined network mania fairly closely, > and while I honestly don't even know what a presentation about it would look > like, I'd always be happy to just chat for a while about if it there's > interest. (One little teaser - a good segment of it involves running Linux > directly on enterprise class network gear!) > > Frank Sweetser fs at wpi.edu | For every problem, there is a solution that > Manager of Network Operations | is simple, elegant, and wrong. > Worcester Polytechnic Institute | - HL Mencken > > On 01/21/2015 10:43 AM, Tim Keller wrote: >> 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". >> >> >> _______________________________________________ >> Wlug mailing list >> Wlug(a)mail.wlug.org >> http://mail.wlug.org/mailman/listinfo/wlug >> > _______________________________________________ > Wlug mailing list > Wlug(a)mail.wlug.org > http://mail.wlug.org/mailman/listinfo/wlug >

Jan. 26, 2015