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simple question for default gateway, subnet mask

Dear Expert,

I got one computer window 7 and the other window xp computer connected to one ADSL device which has one phone line and 4 external port for connection, of couse, also have AC charger connection.
Recently, I have been studying ssome network tutorial about, switch, ADSL, router, gateway, subnetwork, subnet mask. sometimes, get confused with those technical term.
So try to bring up some questions as follows:
When I type ipconfig on window 7 command line, it will show me as these

PPP adaptor:
DNS SUffix:
IP address:218.102.165.23
Subnet Mask: 255.255.2555.255
Default Gateway:0.0.0.0

Ethernet Adaptor:
IP address: 169.254.109.43
Subnet mask : 255:255:0.0
Default gateway:

Question-1: The gateway is refered to my ADSL device, Right ?
Question-2: Default Gateway address is address to locate to my ADSL device, Right ?
Question-3: Why it is 0.0.0.0 as I know from the tutorial, 0.0.0.0 is not allowed ?
and 0.0.0.0 is meaning not connecting to netwrok, Right ?
Question-4:subnet mask 255.255.255.255.255 is allowed, Right ? but what class of address,
Class A,B,C,D, E ?
Question:5- Finally question all IP address and subnet mask is automatically given by my ISP company when I do internet connection nowsday, right ? As my memory for ten year ago, we needed to type subnet mask by user before connection, Why ?

Please advise
Duncan

I wonder if you are reporting the correct device. The subnet mask on a machine connected to the router portion (4 ports) of your ADSL modem should be 255.255.255.0.

Open cmd.exe again and type ipconfig /all

Look through and make sure you are looking at the section for your Ethernet device. It should come out differently than the above.

Please let us know.

.... Thinkpads_User

ASKER

Whatever I change to port location 1,2,3, or 4, it will report subnet mask 255.255.255.255.
Why ?
there are 4 ports on ADSL deivce, so it will four different subnet mask address, Right ?

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Subnet mask has nothing to do with what port you plug in to. Subnet mask can be described as a way to determine the size of the network. 255.255.255.255 is one host, 255.255.255.0 are 254 hosts, etc.

I see you have a PPP adapter and an Ethernet adapter. So do you need to set up a PPP connection to your router to get to the internet?

there are 4 ports on ADSL deivce, so it will four different subnet mask address, Right ?

No. The subnet mask will be the same for all computers on that one subnet. See my wireless IPCONFIG. I have a router in front of the cable modem and that is where I get my addressing. See below.

Wireless LAN adapter Wi-Fi:

Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::75d8:c8e3:62ac:4ff%13
IPv4 Address. . . . . . . . . . . : 192.168.100.102
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.100.1

In your case, the router is built into the ADSL device and the IP address from the router should be internal (like 192.168.1.x) and not external (218.102.165.23).

Now I should have looked more closely as your Ethernet device has a 169.254.x.x IP which is the NOT Connected auto configuration IP.

Disconnect both computers from the ADSL device. Now unplug the ADSL device, wait 2 minutes and plug it in. Wait 2 more minutes and connect ONE computer only via Ethernet cable to the router port on the ADSL device.

Now what does IPCONFIG tell you?

ASKER

Yes, I need to PPP connection from window with my passoword and login to log into my ISP

Once logged in and connected, you should still get an internal IP address.

Ask your ISP how to set up the PPP connection from a web browser that logs into the ADSL device.

Once connected via a web browser window you should be able to close the window and you should have an internal IP address as I noted above.

.... Thinkpads_User

ASKER

Hi guys, both computer are well connecting to internet so internet connection is no problem
at all, but all subnet mask is 255.255.255.255 for both computer. So no need to contact my ISP

You must be looking at the wrong device with IPCONFIG.

Two computers connect to a router both with Internet on one ADSL modem with one phone line will not give (a) an external IP address and (b) will not have a subnet mask of 255.255.255.255.

You are reporting the external connection and asking why?

Find the internal connection and report on that. It will be different.

... Thinkpads_User

ASKER

Dear thinkpad_users,

just follow instruction, just up one computer after disconnection power of ADL and start it
again, it report same subnet mask of 255.255.255.255. gatway is 0.0.0.0 and
ethernet Ip is still similar to 169.254.109.43. ( not as you say 192......)

But I found one thing DPCH is enabled for ethernet adaptor
and DPCH is NOT enabled for PPP adaptor after using ipconfig/all

169.254.109.43 is the auto configuration IP and that device will not get internet - no way.

So you are reporting on the wrong device.

Please do an IPCONFIG /ALL and post it here.

Also, you may have changed TCP/IP on your computer and messed it up.

Follow the link below from Microsoft to reset TCP/IP.

http://support.microsoft.com/kb/299357

I think you may have set one or both your computers up with STATIC IP addressing and that is usually not a good idea.

.... Thinkpads_User

ASKER

Dear Thinkpad_users,

You might be wrong, there are two portion
one is PPP adaptor connection and Ethernet Adaptor connection
PPP is connecting to internet
Ethernet is connecting to internal LAN network
so when you do ipconfig/all you will report PPP and Ehternet connection information for you
Right ?
AND Sorry last typing DPCH is not correct that should be DHCP instead

Whatever, my internet connection and ethernet connection is well connected
and I can browser any location in internet for both computer and then I also able to
ftp file from one computer to the other computer on my network, so all TCP/IP
connection is good. so you don't need to focus on connection issue

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ASKER

169.254.109.43 is Ethernet IP address for private IP addressing that is internal address
for ethernet LAN network that is generated by auto configuration. SO when you need transfer file by ftp from one computer to other one at your home PC network, you need that

So don't confuse, 169.254.109.43 is NOT IP address for internet

ASKER

it seems erniebeek sounds correct since nowsday we are using PPP (point to point protocol)
so it would set 255.255.255.255 whatever using window 7 or Xp

I got two computers connecting to one ADS using window & and window XP for one and other computer respectivelyL

ASKER

Thinkpad_user, you understand more about what we are asking question ?

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@Thinkpads_User: Crosspost :)

And it seems we disagree on some points.

@erniebeek - we are not too far apart :)

I think we just posted differently on 0.0.0.0 . Placeholder is probably better language. I just said it is under the control of the ISP.

.... Thinkpads_User

ASKER

Dear Thinkpad_user,
since I am using Chinese version of window, so I could not send ipconfig output to you.
I just have these translation to english:

First computer with window 7 for ipconfig output:
=======================================
PPP adaptor:
DNS SUffix:
IP address:218.102.165.23
Subnet Mask: 255.255.2555.255
Default Gateway:0.0.0.0
DHCP Enable: NO

Ethernet Adaptor:
IP address: 169.254.109.43
Subnet mask : 255:255:0.0
Default gateway:
DHCP Enable: YES

Second computer with Window XP for IPconfig output
==============================================
PPP adaptor:
DNS SUffix:
IP address:218.102.198.88
Subnet Mask: 255.255.2555.255
Default Gateway:218.102.198.88
DHCP Enable: NO

Ethernet Adaptor:
IP address: 169.254.39.175
Subnet mask : 255:255:0.0
Default gateway:
DHCP Enable: YES

ASKER

it is good for me from your reply at least know more network stuff and trigger more
questions

ASKER

On second computer the Default gateway is same as IP address of PPP

ASKER

Both IP address for ethernet adaptor are generated by auto configuration(be reminded)

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Agree with thinkpads_user. And again, like said, the Default gateway is irrelevant with a PPP adapter.

ASKER

after go throught ipconfig/all result on two computer, there are no such address
about 192.168.1.X, so there is no such address of 192.

I had seen before, sometimes, it will go to 169.254.x.x and sometimes go to 192.168.x.x
for ethernet IP addresss from auto configuration.
Anyway 192.168.x.x or 169.254.x.x is just for auto IP for ethernet, so don't just put too much focus on that

ASKER

As you mean, default gateway is related to ethernet Adaptor instead of PPP adaptor?
SO what is default gateway for my case?

Eniebeek or Thinkpad_user

But this question is about understanding PPP and the working of your ADSL router.
I suppose your internet connection is operational on both machines via the PPP adapter?

ASKER

So could I conclude the default gateway on my two computer is no use or no meaning since
both computer are using PPP connection , RIght ?

ASKER

both computer are using PPP connection, Yes

ASKER

why both subnet mask are same(255.255.0.0) if they connect to different port on ADSL
Is it okay for the same ?

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both computer are using PPP connection, Yes

I did miss above that you have TWO external IP addresses. I had assumed ONE because you have one phone line.

So you get internet by External IP (which is fine) but the subnet mask, gateway and DNS are all under the control of the ISP.

So sorry, you are not using an internal network - only external IP addresses.

.... Thinkpads_User

ASKER

I tried not to use ADSL(so PPP is not connected) and directly connected two PC through one cable and both report 169.254.x.x. auto IPv4 address and I successfully using FTP filezilla to transfer from each others by typing 169.254.x.x., username, password, port21
that experiemt proving ethernet is using 169.254.x.x. IPv4 address

Again, the subnet mask has nothing to do with which port you use on your router. Read about APIPA, the network address is 169.254.0.0 so the corresponding subnet is 255.255.0.0.

I tried not to use ADSL(so PPP is not connected) and directly connected two PC through one cable and both report 169.254.x.x. auto IPv4 address and I successfully using FTP filezilla to transfer from each others by typing 169.254.x.x., username, password, port21
that experiemt proving ethernet is using 169.254.x.x. IPv4 address

That is correct. If the two machines are physically connected then, thanks to the APIPA addresses, they are in the same network and should be able to communicate with each other.

To repeat: 169.254.x.x will NOT give you internet. It won't. If it does FTP fine, but that is not internet.

But you ARE using TWO external IP addresses (218.x.x.x) for internet.

... Thinkpads_User

ASKER

So the conclusion:

A-PPP connection is no need default gateway, Right ?
B-subnet mask 255.255.0.0 or 255.255.255.0 or 255.0.0.0 is not related to which port of
ADSL is connected, Right ?

Both are correct (A and B :)

ASKER

Yes as I said 169.254 is only for internal not for internet.

Erniebeek wrote "If the two machines are physically connected then, thanks to the APIPA addresses, they are in the same network and should be able to communicate with each other. "

Yes, indeed, but two machines connected will not get internet via 169.254.x.x. In this case, internet is coming from external IP addresses.

@duncanb7 - Erniebeek and I are saying very similar things. We just say it in different ways.

... Thinkpads_User

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A-PPP connection is no need default gateway, Right ?

No. It needs it. You just do not have it and you can't get it.

B-subnet mask 255.255.0.0 or 255.255.255.0 or 255.0.0.0 is not related to which port of
ADSL is connected, Right ?

Yes, but that doesn't relate much because the subnet mask you have is related to 169.254.x.x and does not relate to your internet.

..... Thinkpads_User

ASKER

A-PPP connection is no need default gateway, Right ?

No. It needs it. You just do not have it and you can't get it.

===========================

Thinkpad_user, but why I still connect to internet with default gateway 0.0.0.0
if PPP connection needs default gateway ?

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ASKER

How you do that to log on ADSL, could tell me how ?

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ASKER

@duncanb7 - As we have said: On your computer, the gateway of the External IP is just a placeholder. The ISP is in control of it.

thinkpad_user, you mean for my window 7 computercase default gateway 0.0.0.0 is just buffer or file or memory in my PC and controlled by ISP, Right.

BE reminded, I also use xampp server for both PC, is it affected default gateway setting ?

ASKER CERTIFIED SOLUTION

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ASKER

thanks for all of your reply please don't mind the point allocation in this thread
since I also get a liitle bit confused from the reply

I will write new thread to continue this topic

@duncanb7 - Thanks and please do ask a new question. Keep it very simple so as to help yourself.
.... Thinkpads_User

ASKER

http://en.wikipedia.org/wiki/Default_gateway for memo only

ASKER

when you mention192,168.X.X ip address that might be
the old stuff for using dial-up connection(single modem) and nowsday
using broadband connection(using DSL) for auto configuration.

So that is why my IP address is 203.x.x.x or 218.x.x.x

@duncanb7 - 192.168.x.x is not old, it is a current internally routed address that does not appear in the external world. The other addresses you pointed to are external addresses (from your ISP). You are using external addresses for your two computers because you have two external IP addresses.
... Thinkpads_User