Default router and DHCP

Question

Level 1

11 points

Default router and DHCP

I connect to a WiFi router with internal DHCP server. When I set my MacBook Pro to get its address via DHCP, it gets the proper DNS and default gateway addresses, but can't reach the Internet.
If I manually assign an IP address, and enter the same default gateway address as what comes down from DHCP, everything works OK.

How can I get my Internet connection to work properly while using DHCP?

MacBook Pro, Mac OS X (10.4.10), iPod, iMac G5, iBook G4

Posted on Sep 27, 2007 3:13 PM

Reply

Answer 1

jdelima

Level 3

515 points

Sep 27, 2007 5:05 PM in response to AppleNovice

The only logical conclusion here is that you are NOT getting correct details via DHCP. Can you list the addresses that you are assigned via DHCP and what you input? IP Address, Gateway, Netmask, DNS. I would assume that there is some disparity in what is entered versus what is provided.

Also try pinging out of the connection when you have DHCP assigned details and see what happens (use your manually input details as a reference point when testing). Try to ping somethign like www.google.com, the gateway, and the DNS server(s). I think you'll find that more than likely you have issues getting to the gateway and/or DNS server(s) when you're using DHCP.

Reply

Answer 2

AppleNovice Author

Level 1

11 points

Sep 27, 2007 8:13 PM in response to jdelima

Pinging revealed that the connection beyond the gateway is indeed the issue. What could cause the "dynamic" part of DHCP to not function?

Reply

Answer 3

KJK555

Level 4

2,906 points

Sep 27, 2007 10:11 PM in response to AppleNovice

Probably a DNS problem.

Under the Network Preference Pane on your Mac go to the TCP/IP tab
(make sure that under the "Show:" drop down list it reads "Built-in Ethernet".

Configure: Using DHCP
IP Address: (will fill in automatically)
Subnet Mask: (will fill in automatically)
Router: (will be blank)
DHCP Client ID: (leave blank)
DNS Servers: (use DNS info from your Cable/Dsl ISP)
Search Domains: (can leave blank)

Reply

Answer 4

AppleNovice Author

Level 1

11 points

Sep 28, 2007 7:37 AM in response to KJK555

Selecting "Built-in Ethernet" with "Using DHCP" in the Config IPv4 drop down actually empties the IP Address, Subnet Mask, and Router data.

Reply

Answer 5

KJK555

Level 4

2,906 points

Sep 28, 2007 10:38 PM in response to AppleNovice

Sorry, I gave you nic card directions. You will have to select your aircard instead. The point is to manually add the dns (domain name server) settings and leave the other settings blank. You will have to get the dns addresses from your internet provider.

Reply

Answer 6

KJK555

Level 4

2,906 points

Sep 29, 2007 10:33 PM in response to AppleNovice

Oh BTW: Be sure and check the dns settings in your router. Normally the router manufacturer allows the DNS addresses (of your IP) to be entered manually as well. Many times entering those addresses will clear up the connection issues. Also in the LAN settings on your router you should have a check box to enable/disable DNS Relay. Normally should be enabled so as to pass on DNS services to your computers/LAN network.

Reply

Answer 7

jdelima

Level 3

515 points

Sep 30, 2007 10:09 PM in response to AppleNovice

So which ping exactly fails? To the gateway? Can you list your IP details (nothing will be compromised as these are LAN details so it doesn't matter)? List IP address; DNS servers; gateway address; netmask.

It'll more than likely be something simple that you'll slap yourself for! : )

Reply

Answer 8

AppleNovice Author

Level 1

11 points

Oct 3, 2007 7:56 AM in response to jdelima

Here at the office, we are all on a NAT'ed subnet of 192.168.0.0/24.

Internet access fails with the normal configuration for the machine.

If I try to ping sites that respond to pings - like Yahoo or The Whitehouse - those attempted pings fail because the name lookup (www.yahoo.com) fails.

I can ping the LAN side of the gateway, but I can't ping through it to anything on the Internet. All nslookups fail. Attempts to ping a site's IP address (69.147.114.210 for Yahoo today - obtained from a different computer) result in 'host unreachable.' So the symptom is that I can't route "through" the gateway.

All PCs on the network work properly, and my Mac works properly if I forgo DHCP and enter the IP configuration manually. In that dialog box, I can enter the IP address of the gateway. If I use DHCP, the DHCP server provides the same gateway address and same DNS addresses, but I have all these problems. And unlike Windows, it looks like I can't use DHCP but override the gateway address.

Reply

Answer 9

AppleNovice Author

Level 1

11 points

Oct 9, 2007 6:31 AM in response to jdelima

This is so frustrating! This is the connection I use at the office and I'm sure it is going to be one of those "Duh!" moments, especially considering that all other machines are connecting without problems.

The following are listed when reading the TCP/IP data fro "Using DHCP" for IPv4 config:
IP address 192.168.0.20, Subnet Mask 255.255.255.0, DNS Servers 66.174.3.7 and 69.78.92.14.

Reply

Answer 10

AppleNovice Author

Level 1

11 points

Oct 9, 2007 8:41 AM in response to AppleNovice

What's really frustrating is that the connection is there! Internet connection shows status "Connected to 'Network'" with full signal strength... it seems that the dynamic addressing is not working-- maybe? I can't understand why the computer is picking up the signal but not making the connection to the internet... but it is working fine on my Windows machine. UGH.

Reply

Answer 11

jdelima

Level 3

515 points

Oct 9, 2007 8:37 PM in response to AppleNovice

Don't suppose you've got any proxy servers there? All "connected to network" means is that you have a live connection from your Mac to the next hop (could be a an ethernet cable that is connected from your mac to a switch, with the switch connected to nothing else for all your Mac cares!).

Have you actually tested pinging addresses from your PC? That's your positive control. Your firewalls may be set to drop ICMP (ping) traffic. If that's the case, then trying to ping something is not a useful test. Given that you can ping to obtain an IP address from another machine in the office, i'd say you have a DNS issue somewhere too. Confirm that the other machines are not actually using an internal DNS server (it's unlikely they'll use an external DNS server as a primary). What is used at the office? Is it an Microsoft Active Directory site?

There is definitely something different between the DHCP details and the static ones. That is the only way that you can have differing results like that (unless it is not an IP problem but something external to it such as a proxy).

Reply

Answer 12

AppleNovice Author

Level 1

11 points

Oct 10, 2007 6:13 AM in response to jdelima

Yes, I'm one of the few, the proud, the Mac owners. The PCs are having no problem connecting to the internet -- that's what I'm using to communicate here. It's got to be some setting on my Mac that's not set correctly, but I've looked and tested each one that I know of... and no luck. I seem to always have this problem when I connect my computer to a new network, like I did this weekend on vacation. Yet, the settings for connecting at work should not be affected-- no proxy change. I've checked the password and like I said, the Mac sees the network, reads the strength of the signal, but won't connect. What else could cause this problem of seeing the network, but not connecting through?

Reply

Answer 13

KJK555

Level 4

2,906 points

Oct 10, 2007 12:44 PM in response to AppleNovice

Obvious your Mac is not communicating properly with the router's DHCP client for whatever reason. It could be some communication or address errors or protocall problem. Maybe one or the other just isn't giving a response the other one understands when requested. Usually its the window machines that balk at network connections, but occasionally a Mac or Unix machine will have trouble connecting to a certian brand/model of router. Perhaps the router you are trying to connect to is optimized for connecting to windows machines. At any rate, the problem is probably in the router, not your Mac .

Here are a couple of things more than you can try:
1. Enter the router's MAC address in the "DHCP Client ID" box in your air card network settings page.
2. Turn off IPv6 (in your air card network settings page).
3. Enter your router's gateway address in the DNS settings box (in your air card network settings page).
4. Try "using DHCP with manual address" mode.

Reply

Answer 14

AppleNovice Author

Level 1

11 points

Oct 11, 2007 11:11 AM in response to KJK555

Some jerk hi-jacked my assigned IP address (By my thinking they should be assigned dynamically-- who knew?).

By manually entering all the address data-- IP, router, Subnet, etc., I was able to establish the connection WITH throughput. BTW, the proper addressing, which I got from a peer who also uses a Mac, somehow eluded our Windows brethren.

It is frustrating for my computer to tell me that it is connected to the network but it can't quite diagnose the inability to actually connect with throughput. Perhaps I would suggest the Apple engineers look into, maybe adding a more robust diagnostic tool? 'Cause you know, you make it idiot proof and the world just makes better idiots!

Now, I had the network set for "Automatic," is that what caused the hiccup? I wonder.

Thank You so much for your help!!!

Reply

Answer 15

KJK555

Level 4

2,906 points

Oct 11, 2007 3:14 PM in response to AppleNovice

That guy probably had his IP address entered manually. Whenever you use a manual ip address on a network that you are not the administrator of, it is best to use one assigned by your administrator and/or use one well above or below the ip range assigned to everyone else by the DHCP client.

eg: if the DHCP client assigns IP's in the range of 192.168.0.100 - 192.168.0.200 then use you should one like 192.168.0.311 to reduce possibilities of having conflicts.

No, os x won't alarm you ( other than refusing to connect ) about a IP conflict situation, but neither will anyone elses OS that I know of.

I prefer manual IP configuration whenever practical and/or possible.

Reply