Macbook Ethernet Connection Issue

salguod

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I am having a bit of a problem with my mid 2007 Macbook. Specs: Processor Name: Intel Core 2 Duo
Processor Speed: 2.16 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 1 GB

Whenever I log into OS X and plug in the ethernet cable to my macbook to go on the internet (this is the university network in the halls of residence), it connects to the local network fine, i.e. I am able to see shared computers on the network in the halls where I am and I can see shared libraries in itunes, but whenever I try and log onto the internet it doesn't connect. Looking at my iStat widget it shows an ip address but it doesn't show an external ip address, it only says it is updating.

Restarting doesn't solve this problem as it stays on updating the external ip and so I cannot connect. I left it for 5 hours on Saturday afternoon to which it still didn't connect.

The only workaround I have found which isn't very convenient is whenever I want to go onto the internet on OS X, I have to shut down, boot up in XP via BootCamp, go onto the internet briefly, shut down, the reboot in OS X again, where magically the internet is working, and I have an external ip address.

If, I close the clamshell of the laptop, or if I let it go to sleep, I have to go through the whole process of booting into XP and then back into OS X.

I would also like to point out that the wifi is working fine, I can connect to it fine when I am on campus or at home, it is just whenever I am trying to connect via ethernet in my room, which incidentally is the only place where I connect using the ethernet that it doesn't work, and sadly that isn't an option in my room as there is no wifi access. This problem has only occurred in the past 5 days or so, I had been able to connect fine using the ethernet cable since September when I started. Also I haven't changed any network configurations.

Also, no one else seems to have this problem, my flatmates computers are working fine (none of them are using a mac though) and also the people I know who are using a mac are not having problems either.

I have googled this problem and only found a few other instances where people are having the same problem, but as of yet I haven't found a solution.

If anyone has any ideas, I'll be highly grateful. :)
 
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PacketCollision

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Run 'ifconfig' and 'netstat -r' from the terminal and paste their results here. 'netstat -rn' may work better if you are having DNS issues (likely).
 
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Clegko

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You can also try flushing your DNS Cache on the laptop. Open the terminal and paste in:
dscacheutil -flushcache
 
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salguod

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Thanks for both of your replies. Annoyingly, it seems to have corrected itself, but the problem with safari not remembering logins has returned, but that is another issue altogether but luckily I'm not the only person with that problem.

PacketCollision, if you want I could still post the results from what I put into the terminal to see if there was anything obvious from it, or does it have to be under the conditions I went into above?
 

WillDAQ

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Not so much It Just Works? as It Just Breaks Then Fixes Itself?

*legs it*
 

salguod

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Not so much It Just Works? as It Just Breaks Then Fixes Itself?
:lol: Very true.

I didn't do anything different to any other time I switched it on, and haven't done anything different whilst using it, which makes it even more annoying because I don't know what to do if it happens again.
 

PacketCollision

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If you are worried it will happen again, run those commands and save the output (paste it here or just save a log of the terminal window). That way, when it does happen again, we can compare the working output with the broken output.

Basically, "netstat -r" prints out the routing information that your computer is using (what computer it has to talk to to send things out to different networks, including the Internet), and ifconfig just shows some basic information about your network connections.
 

salguod

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It's doing it again, so I ran those commands (netstat -r and ifconfig) in terminal and saved them, so I have a version from where it isn't working and one from where it is, so you can compare them.

Netstat-r when working fine said:
Routing tables

Internet:
Destination Gateway Flags Refs Use Netif Expire
default 134.36.102.1 UGSc 66 29 en0
127 practivate.adobe.c UCS 0 0 lo0
practivate.adobe.c practivate.adobe.c UH 0 0 lo0
134.36.102/23 link#4 UCS 4 0 en0
134.36.102.1 0:0:c:7:ac:66 UHLW 66 6 en0 759
host063.westparkvi practivate.adobe.c UHS 0 0 lo0
host078.westparkvi 0:11:11:e1:bc:ac UHLW 0 352 en0 1124
host087.westparkvi 0:1d:9:d7:4f:19 UHLW 0 75 en0 1124
134.36.103.255 ff:ff:ff:ff:ff:ff UHLWb 0 4 en0
169.254 link#4 UCS 0 0 en0

Internet6:
Destination Gateway Flags Netif Expire
localhost link#1 UHL lo0
localhost link#1 UHL lo0
fe80::%en0 link#4 UC en0
douglas-woods-macb 0:19:e3:3a:8d:3f UHL lo0
ff01:: localhost U lo0
ff02:: localhost UC lo0
ff02:: link#4 UC en0
Netstat-r when not working said:
Routing tables

Internet:
Destination Gateway Flags Refs Use Netif Expire
default home UGSc 2 3 en0
127 practivate.adobe.c UCS 0 0 lo0
practivate.adobe.c practivate.adobe.c UH 0 0 lo0
169.254 link#4 UCS 0 0 en0
192.168.1 link#4 UCS 2 0 en0

192.168.1.71 practivate.adobe.c UHS 0 0 lo0
home 0:1a:c4:11:e0:91 UHLW 16 212 en0 1169
192.168.1.255 ff:ff:ff:ff:ff:ff UHLWb 0 6 en0

Internet6:
Destination Gateway Flags Netif Expire
localhost link#1 UHL lo0
fe80::%lo0 localhost Uc lo0
localhost link#1 UHL lo0
fe80::%en0 link#4 UC en0
douglas-woods-macb 0:19:e3:3a:8d:3f UHL lo0
ff01:: localhost U lo0
ff02:: localhost UC lo0
ff02:: link#4 UC en0
ifconfig when working said:
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
inet 127.0.0.1 netmask 0xff000000
inet6 ::1 prefixlen 128
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet6 fe80::219:e3ff:fe3a:8d3f%en0 prefixlen 64 scopeid 0x4
inet 134.36.102.63 netmask 0xfffffe00 broadcast 134.36.103.255
ether 00:19:e3:3a:8d:3f
media: autoselect (100baseTX <full-duplex>) status: active
supported media: autoselect 10baseT/UTP <half-duplex> 10baseT/UTP <full-duplex> 10baseT/UTP <full-duplex,hw-loopback> 10baseT/UTP <full-duplex,flow-control> 100baseTX <half-duplex> 100baseTX <full-duplex> 100baseTX <full-duplex,hw-loopback> 100baseTX <full-duplex,flow-control> 1000baseT <full-duplex> 1000baseT <full-duplex,hw-loopback> 1000baseT <full-duplex,flow-control> none
fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 2030
lladdr 00:1b:63:ff:fe:71:9c:74
media: autoselect <full-duplex> status: inactive
supported media: autoselect <full-duplex>
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 00:1b:63:c1:1c:2f
media: autoselect (<unknown type>) status: inactive
supported media: autoselect
ifconfig when not working said:
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
inet 127.0.0.1 netmask 0xff000000
inet6 ::1 prefixlen 128
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet6 fe80::219:e3ff:fe3a:8d3f%en0 prefixlen 64 scopeid 0x4
inet 192.168.1.71 netmask 0xffffff00 broadcast 192.168.1.255
ether 00:19:e3:3a:8d:3f
media: autoselect (100baseTX <full-duplex>) status: active
supported media: autoselect 10baseT/UTP <half-duplex> 10baseT/UTP <full-duplex> 10baseT/UTP <full-duplex,hw-loopback> 10baseT/UTP <full-duplex,flow-control> 100baseTX <half-duplex> 100baseTX <full-duplex> 100baseTX <full-duplex,hw-loopback> 100baseTX <full-duplex,flow-control> 1000baseT <full-duplex> 1000baseT <full-duplex,hw-loopback> 1000baseT <full-duplex,flow-control> none
fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 2030
lladdr 00:1b:63:ff:fe:71:9c:74
media: autoselect <full-duplex> status: inactive
supported media: autoselect <full-duplex>
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 00:1b:63:c1:1c:2f
media: autoselect (<unknown type>) status: inactive
supported media: autoselect
Here are a couple of screenshots just to show that it says it is connected in the network preferences also what it says on the iStat widget. The ip address starting with 192. from what I can remember is what it uses to connect when using wifi on the Uni network on campus, the 134. one is the one used when it connects via ethernet in my room.


 

PacketCollision

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Hmm, this is a more unusual (and entertaining, for me at least) problem than I expected. It's actually the work of a rogue DHCP server on the network. Basically, someone in your hall has a wireless access point that is configured to give out addresses plugged in to the wall. Your computer is sometimes getting a valid public address from your uni's server, and sometimes getting an invalid private one from your neighbor's router.

To test my theory, some time when the problem is evident, go to http://192.168.0.254 and look at the router's information. Unfortunately, it's a 2-wire, which I think has a secure password by default, so you can't just go in and fix it (disable "assign DHCP lease" or something), but the network admins at your uni should be quite happy to knock on the person's door and explain that the little device they have plugged in (which is probably against the rules for this very reason) is breaking the network for everyone in the building.

As a stopgap, you may be able to manually assign yourself a valid IP address, or just keep requesting DHCP addresses until the correct server gives you one. Depending on how your uni's network is set up, manually assigning an IP might wreak havoc, but you could try it if you want to.
 
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salguod

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Thank you very much. :)

I'm not wanting to be a whistle blower or anything but the next chance I'll get, I'll mention that someone is doing something and I'll have a look into assigning myself a valid ip address if it continues.

The annoying thing, apart from having to restart each time into xp, is that in our agreement we had to sign before coming here it did clearly mention that we weren't allowed to plug in any wireless routers etc, and only 1 thing was allowed to be used at a time to connect to the internet in each room using the ethernet connection.

Thanks again.
 
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