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Ethernet networking problem

CmdrLaForge

CmdrLaForge

macrumors 601
Original poster
Feb 26, 2003
4,677
3,246
around the world
Hello guys,

I need some help - can't fix it by myself.

Today I got a new cable modem. Technican came and installed it and DHCP and the Internet worked fine on his PC laptop. I tried it afterwards on my iBook G4 running Mac OS 10.5.2 and as soon as I plug the Ethernet cable in I get over DHCP an IP adress together with subnet mask and everything. Works just fine on my iBook G4.

Now comes the problem. I can't get it working on my Macbook Pro running Mac OS 10.5.2. It just doesn't receive an IP adress over DHCP. I tried EVERYTHING that I could think of and I do know that the its unlikely that you guys would know an answer but I thought I give it a try.

I attached a screenshot of the working iBook network configuration. On the Macbook Pro the IPv4 adress just stays empty.
Thanks a lot
LaForge
 

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I don' have a MBP so I'm not sure if it has a link indicator light on its ethernet port. But there should be a green light next to the ethernet plug on your cable modem. Does it light (in the same color) when you plug into either laptop?
 
jpsalvesen said:
I don' have a MBP so I'm not sure if it has a link indicator light on its ethernet port. But there should be a green light next to the ethernet plug on your cable modem. Does it light (in the same color) when you plug into either laptop?
Click to expand...

The laptops have no green light indicator but the Ethernet status on both machines show conncted as you can see in the attached screenshot. In other words. The Macbook Pro recognizes that I plug in a Ethernet cable.
 

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Allright!

Next: Can you please switch to english language, and then dump the ethernet tab of the network configuration on both systems? (Or at least verify that they are identically condfigured since you're probably having a hard time getting something out of the MBP)

Also, have you checked if there are differences in the firewall configuration?
 
The only reason I can think of that your MBP cannot obtain an ip, is that it is either on a different subnet or in the wrong range. DHCP will only go so far, ensure that you have not put any other static settings into your config.
 
I just tried to connect to the Internet on my MBP using the Internet-Sharing function on the iBook. The MBP does see the iBook but its again the same problem - it doesn't receive an IP adress.

I am using the network utiliy on the MBP and there I can see that it did receive and sent some packages.

I didn't receive or sent any packages on tcp but on udp 690 datagrams received whatever that means. On ip I did receive 548 packets.
 
Try restarting the modem...

The reason why it may not be working on the MBP is that the cable modem has given it's only DHCP address from the ISP to the iBook. When the iBook was plugged into the cable modem via ethernet, the cable modem links the DHCP address with the MAC address of the iBook. So, that is why you cannot just unplug the iBook and plug in the MBP. Try restarting the cable modem after unplugging the iBook and then plug in the MBP. A cable modem does not work like a router where it just drops hosts off the DHCP address table when they lose their connection. The cable modem talks back to the ISP with the DHCP address it gives out and the MAC address of the device that it gave it to for tracking IP addresses from the ISP's DHCP server.
 
jpsalvesen said:
Allright!

Next: Can you please switch to english language, and then dump the ethernet tab of the network configuration on both systems? (Or at least verify that they are identically condfigured since you're probably having a hard time getting something out of the MBP)

Also, have you checked if there are differences in the firewall configuration?
Click to expand...

I am not sure how to switch the whole system to english. I did compare the configurations and I even tried to manually enter the IP adress from the iBook (the one it received via DHCP)

I opened up the firewall on the MBP - no change.

The network utility (found under apps/utilitys) clearly shows once I plug the ethernet into the MBP that it is then connected with 100MBit/s

andy.barron said:
The only reason I can think of that your MBP cannot obtain an ip, is that it is either on a different subnet or in the wrong range. DHCP will only go so far, ensure that you have not put any other static settings into your config.
Click to expand...

How can I reset that ?
 
Network Problem

Change to Use DHCP with manual Address. Give you MAC the IP 91.65.212.3 -----
The OS should then do the rest. This will also refresh the ARP table in the router. Also check the Router IP range allows more 1.
 
Avenger23 said:
The reason why it may not be working on the MBP is that the cable modem has given it's only DHCP address from the ISP to the iBook. When the iBook was plugged into the cable modem via ethernet, the cable modem links the DHCP address with the MAC address of the iBook. So, that is why you cannot just unplug the iBook and plug in the MBP. Try restarting the cable modem after unplugging the iBook and then plug in the MBP. A cable modem does not work like a router where it just drops hosts off the DHCP address table when they lose their connection. The cable modem talks back to the ISP with the DHCP address it gives out and the MAC address of the device that it gave it to for tracking IP addresses from the ISP's DHCP server.
Click to expand...


You (and all the others who tried to helped me!) are great !!! That solved it !

Now - only my MBP works and I am typing this from my MBP.

Ok - that means I need a router. Or at least I assume I need a router. Because I would like to use all my computers with this internet connection. Could I use TimeCapsule for that ?

Thanks a lot to everybody. You are all really great.

Kind regards
LaForge
 
Not a problem on the solution to your ethernet networking problem with your two laptops. I currently use a Linksys WRT54G (802.11g) router here at home. I have my MBP, wife's MB, kids Sony laptop, another PC tower and our gaming devices all connect to the router without any problems. Getting a router will solve your problems on trying to use multiple devices at one time. I spent around $50 for the router. The configuration of the router is very simple right after you get it out of the box. Glad I could help you out there! :D
 
Avenger23 said:
Not a problem on the solution to your ethernet networking problem with your two laptops. I currently use a Linksys WRT54G (802.11g) router here at home. I have my MBP, wife's MB, kids Sony laptop, another PC tower and our gaming devices all connect to the router without any problems. Getting a router will solve your problems on trying to use multiple devices at one time. I spent around $50 for the router. The configuration of the router is very simple right after you get it out of the box. Glad I could help you out there! :D
Click to expand...

Thanks again . Do you think the TimeCapsule would work as well ? I could use it as a backup and Wifi device and it looks therefore interesting to me.
 
CmdrLaForge said:
Thanks again . Do you think the TimeCapsule would work as well ? I could use it as a backup and Wifi device and it looks therefore interesting to me.
Click to expand...
You could go with the TimeMachine from Apple... it probably would work good for your setup there. I just thought I would share my experience with the equipment that I've used and have recommended to other people.
 
Avenger23 said:
You could go with the TimeMachine from Apple... it probably would work good for your setup there. I just thought I would share my experience with the equipment that I've used and have recommended to other people.
Click to expand...

Sure - and I really appreciate it. Its just that I thought about it anyway. The iBook G4 is my wifes computer and I back it up every now and then. With the TimeCapsule I wouldn't have this problem.

Would that mean that once I connect the TimeCapsule I would have to turn off and then on my modem ? I guess so.
 
No, you won't have to restart the modem every time to connect the computers to the TimeMachine. It works just like a router does by distributing addresses and that it has an internal drive to backup data from the computers. You will only have to restart the modem once, the first time you connect it to the modem. The modem will give it's one DHCP address to the TimeMachine and then the TimeMachine will distribute its own addresses to individual machines, just like a router does.
 
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