Evening.
I'm stumped.
Set up is like this:
ADSL point > 2Wire HomePortal 1000HG ethernets to an Airport Extreme = Computer 1 (via ethernet to the A.E.) & Computer 2 (via Wifi from the A.E.).

The computer 2 is having no troubles at all with the internet. I can collect mail from my server, I can go where I please on the internetz.
Computer 1, on the other hand, can't connect to it's mail server but it can collect mail from it's mail server.
It can connect to some sites, but others - autotrader.co.uk for instance - it can't.

The 2Wire portal deals with the DNS stuff - I had been running OpenDNS in order to get my iOS update to work (lots of people reported what appeared to be DNS related issues preventing the download completing).
However, I've since switched back to the service provider settings.
The Airport's connection is set to share a public IP address.

I've run various scripts via Onyx to flush caches etc. and I'm now stuck.
I can't see why my computer's enjoying unfettered access to the internetz where the other one isn't.

EDIT: I should also add my iPhone's connecting fine, but Dad's Android phone's not.
I've restarted everything in the system too.

Have you tried changing the DNS settings to use openDNS on the second machine? See if that helps.

Could it have malware, which is trying to redirect to bad sites?

No to point out the obvious but have you checked the Firewall settings on the HomePortal?

Are the relevant ports open?

The DNS servers are all dealt from the 2Wire router to the Airport. What I change there should be affecting all the devices on the network.



The firewall - the Airport is DMZ'd by the router, and the Airport is running with all the usual ports open.

Are both devices doing NAT? What are all the IPs - for both PCs and all interfaces on both routers?

I've got some screen grabs - if you can spot anything...

G4 on ethernet:
G4's DNS settings
G4's ethernet settings
G4's TCP settings

iMac over wifi:
iMac's TCP settings
iMac's DNS settings

Airport Extreme:
AE's DHCP settings
AE's NAT settings
AE's TCP settings
AE's Internet settings

2Wire:
2Wire network info
2Wire broadband info


Any use?

Erm...

The G4, iMac and Airport Extreme are addressing in the 10.0.0.0/FF.FF.00.00 range.

However, the 2Wire's DHCP range is set to 172.10.0.0/FF.FF.00.00

Also, are you supposed to be connected to ‘Shazam's Base Station’?

That's incredibly confusing on the Airport; it doesn't show you enough information like what the actual LAN IP address is! We can guess that it must be 10.0.1.1 but it doesn't actually say that anywhere...

The WAN settings on the Airport are inconsistent. It is configured to use the private LAN IP of the 2wire for DNS but the public IP as the gateway.

There are a few options with your setup, and the Airport seems to be trying to use half of one and half of another... It's no surprise that you can only access some parts of the internet. What is a surprise is that it's working as well as you say it is!

Option 1: Clever 2wire, Stupid Airport
This is what I would do.
Turn off DHCP on the Airport and assign it a static IP of 172.16.0.254 / 255.255.0.0 with a gateway and DNS of 172.16.0.1
The 2wire is already set up with a private IP of 172.16.0.1 and NAT turned on, but you need to tick the "Enable DHCP"
Make sure the cable from the 2wire is going into a LAN port on the Airport; and not into the WAN port
The 2wire now does everything; the Airport is acting as a Wireless Access Point and a switch. It is not acting as a router.
Your computers should now pick up IP addresses of 172.16.0.33 upwards.
If you require Airport services to be accessible from the Internet, you will need to forward the relevant ports on the 2wire.

Option 2: Clever Airport, Stupid 2wire
Turn off NAT on the 2wire; Tick "Bridge Network". It is now not really acting much like a router; the Airport will use a public IP.
Make sure the cable from the 2wire is going into the WAN port on the Airport; and not into a LAN port (opposite of Option 1)
On the Airport, I'm going to guess the displayed WAN IPs must be correct for it to be working at all:

Configure IPv4 - MANUAL or STATIC
IP Address: 212.139.91.190
Subnet Mask: 255.255.255.252
Router Address: 212.139.91.189
DNS: 8.8.8.8 and 8.8.4.4

Leave everything else as it is; DHCP and NAT enabled.
The computers should pick up I{ addresses of 10.0.1.2 upwards.
The Airport should be accessible on your public IP address.

Option 3: Clever everything (double-NAT)
This is what most non-technical people do, because it's the way it comes "out of the box" and it should "just work".
Enable DHCP and NAT on both boxes
Plug the Airport's WAN into the 2wire.
The reason I would not do this is because it's translating the network address twice, which doubles the chances of a problem occurring as well as introducing unnecessary overheads.

The gateway for the G4 and IMac is the Airport, which is acting as a router and a DHCP server on the 10.0.1.0 subnet.

The Airport has automatically detected which port the 2wire is connected to, and is using that as the WAN port. The Airport is doing NAT and forwarding the computer's requests to the public IP address.

The internal IP of the 2wire is 172.10.0.1 which is being used by the Airport for DNS

The 2wire is clever enough to understand this Bollux up setup by detecting the Airport (which is called Shazam's base station) on the LAN side despite it's public IP assignment. This is the little miracle which makes it half-work.

But that's not ...

... no no...

... why ...

...

... no no no no no no no no no no no no no no no...

That was my reaction when I saw the Airport screenshots. I needed a little lay down before I replied

Same here.

I am ... stunned.

Note to Prof - you may want to print this out or copy - paste to a document because you'll be off-line while you're half way through!

Prof?

Oh dear, too late..?

Tried option 1. Airport errored saying there was a double NAT and an unplugged Ethernet port.
Then option 2 meant that while I was connected to the airport, I couldn't see the 2Wire at all, and can't manage it's settings until I've got the airport talking to it again.
I'm sending this from my phone.

The Airport really isn't very... "normal", is it! You can buy a "normal" AP for about £15 which would make life simpler..?

With option 1, did you turn off NAT on the Airport? Just untick the "Enable NAT" option. If so, then I don't understand why it would complain about double-NAT. I guess it just has a mind of it's own and ignores what you tell it..?

Also, I'm unclear of the weird terminology on the Internet Connection tab, maybe you can clarify:

I don't know what the options are on the Ethernet WAN port drop-down list but we're looking for something like "None" or a numbered port which you leave unplugged. This may not be necessary depending exactly what the thing decides to do when you turn NAT off - this is unknown to me because you just don't have that option on a normal router; the WAN port is usually separate and clearly labelled.

What are the options on "Connection Sharing"? We don't want "Share a public IP address" - we don't want the box to do any routing at all.

Basically, because we want the Airport to just STFU and stop breaking things by getting in our way, provided the IP address settings are correct and DHCP and NAT are disabled, none of the other options should really matter. We just want it to work like a cheap switch would and join everything together.