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can't connect to internet or even ping nameserver [solved]
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kaibutsu
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PostPosted: Mon Dec 03, 2007 12:49 pm    Post subject: can't connect to internet or even ping nameserver [solved] Reply with quote

The problem is that I can't connect to the internet. It's very sudden; last thursday things just suddenly stopped working. I don't really know why, and I don't remember changing anything in the last couple days before the problem started.

The computer with the problem is named Biscuit, to avoid confusion below (since there's a second gentoo machine still working).

Details:
+ I am on a university network. Biscuit is connected to a router which picks up the Uni's wireless signal and splits it into four wired ethernet ports. Two other machines (a windows laptop and my other gentoo machine, on which I'm currently typing) also connect to the internet through this router. I've tried changing ports and resetting the router to no avail. Since the other machines are still running fine, I don't think it's a router problem.

+ So normally, to do anything on the internet more complicated than a ping, I need to bring up a web browser and log in through the uni's login page. This page isn't coming up, and the web browser just says "looking for $website...". I can usually still ping things without signing in, but no more: "ping: unknown host: google.com". Biscuit also can't ping either of the nameservers in resolv.conf. (the other gentoo machine can, though.) It CAN ping the Gateway listed by "route -n" and other computers in the university network, such as the two other computers in my dome, and another friend's computer that connects through the university wireless system.

+ After restarting my eth0 with "/etc/init.d/eth0 restart" I get at seemingly random intervals on my terminal messages to the effect of "ERROR: Name or Service not found." I've also seen a couple "Temporary failure in name resolution" messages.

+ I've tried a lot of things described in the forums. I've already tried rebuilding the kernel, and re-installing dhcpcd with 'vram' use flag enabled.

Any ideas? Thanks!


Last edited by kaibutsu on Tue Dec 04, 2007 1:17 am; edited 1 time in total
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kaibutsu
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Location: davis, ca

PostPosted: Mon Dec 03, 2007 12:59 pm    Post subject: additional info... Reply with quote

Here's some hard data:

Code:

route -n

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
128.120.57.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo
0.0.0.0         128.120.57.254  0.0.0.0         UG    0      0        0 eth0


Code:

ifconfig

eth0      Link encap:Ethernet  HWaddr 00:40:63:E7:2B:2C 
          inet addr:XXX.XXX.XX.XX  Bcast:128.120.57.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:509854 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3813 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:49140129 (46.8 Mb)  TX bytes:638576 (623.6 Kb)
          Interrupt:10 Base address:0xa000


(the XXX.XXX.XX.XX is my usual ip address)

Code:

resolv.conf

# Generated by dhcpcd for interface eth0
search ucdavis.edu
nameserver 169.237.250.250
nameserver 169.237.1.250


All of this pretty much duplicates the data from the working machine, except the resolv.conf. The working machine has "domain ucdavis.edu" instead of "search ucdavis.edu", but it's also running a much older version of dhcpcd, so I'm not sure that's a problem.

Thanks again.
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kands
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Joined: 01 Apr 2003
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PostPosted: Mon Dec 03, 2007 4:03 pm    Post subject: Reply with quote

That is strange. If you're doing any bit torrentish type traffic the university may have blocked your mac address???

if you boot with a live cd are you able to access the internet using links or lynx?
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kaibutsu
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PostPosted: Mon Dec 03, 2007 5:27 pm    Post subject: Reply with quote

I'm not running any bittorrent or peer-to-peer stuff; just use the computer for internet things. I've emailed the university network people and asked if I've been blocked or anything like that, but haven't heard back. I'll try the livecd when I get home.

Is there a way to get a list of the networking software used by the machine? I might try going through things systematically and rebuilding, in case there's any bitrot occurring...
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kands
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PostPosted: Mon Dec 03, 2007 5:45 pm    Post subject: Reply with quote

Gentoolkit has some useful utils.

http://www.gentoo.org/doc/en/gentoolkit.xml

Look at equery list -i to see what is installed on your system. add a parameter after the -i to narrow your search.
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Hu
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PostPosted: Mon Dec 03, 2007 10:32 pm    Post subject: Re: can't connect to internet or even ping nameserver Reply with quote

kaibutsu wrote:
Biscuit also can't ping either of the nameservers in resolv.conf.


This sounds like the root of your problem. Without nameserver access, Firefox will not be able to find the login page for you to authenticate. If you have the working Gentoo machine resolve the address of the authentication page, can you reach that page by IP address from Firefox on Biscuit? What is the output of traceroute 169.237.250.250?
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kaibutsu
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PostPosted: Mon Dec 03, 2007 10:37 pm    Post subject: Reply with quote

I agree; no nameservers is bad. But it seems like I also can't ping things by number, when I try to.

The traceroute from the working machine follows; Biscuit doesn't seem to have it installed.

Code:
traceroute to 169.237.250.250 (169.237.250.250), 30 hops max, 40 byte packets
 1  128.120.57.254 (128.120.57.254)  6.181 ms  7.094 ms  7.714 ms
 2  169.237.249.241 (169.237.249.241)  8.520 ms  35.480 ms  57.315 ms
 3  area42--area0.ucdavis.edu (128.120.0.229)  25.366 ms  31.056 ms  43.324 ms
 4  area0--area13.ucdavis.edu (128.120.0.122)  53.299 ms  67.929 ms  69.720 ms
 5  * * *
 6  * * *
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kaibutsu
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PostPosted: Tue Dec 04, 2007 1:17 am    Post subject: solved! Reply with quote

Ok, seem to have fixed it by changing my (reported) MAC address with

Code:

mac_eth0="random-samekind"


Probably the uni saw fit to persecute me for some reason... we'll just have to keep them guessing at my mac address until they see fit to actually talk to me.

Thanks everyone!
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