Travel Forum / Travel Types / RV Travel / August 2008

Being wireless when you are normally on cable is most likely the
conflict. Try setting up 2 accounts, 1 on the cable and 1 wireless. I
use to be a computer guru so get a 2nd opinion - make that 3rd!!

Tom J

GB,

You might want to check your firewall setting in your router.  Sounds like
one of your IP addresses might be blocked in your router.  The problem is
probably caused by a setting in the router.  There should be a way to access
the router and reset it to the factory defaults if the problem seems to be
the router.  Many routers use http://192.168.0.1/ to access the setup menu.
If you aren't sure on how to do it, try doing a hard reset.  Refer to the
manual for hard reset.

It means that 2 computers on the LAN are trying to use the same IP address.
specifically, your machine is seeing 'other' traffic with the address that
it thinks of as 'its own' in the 'source' address field.

It's 'hide and seek' time  <wry grin>

First, you have to _find_ the other machine, and then change the IP address
associated with _one_ of the conflicting machines.

There are _several_ ways of dealing with this matter.

*IF* you always use your computers on your internal 'network'  (just you
folks and the router), the 'most permanent' thing to do is assign 'fixed'
addresses to the machines.  that way you "know" they won't conflict with
each other.

If you -don't- have fixed addresses for the machines, then when you get a
problem, you can go to the 'network connections' panel, click once on the
interface you're using to connect with (to select it), then right-click
and select 'disable' from the pop-up menu.  wait 10-15 seconds, and right-
click again, this time select 'enable' from the menu.

This will get you a new address, and you _should_ be back in business.

Rebooting the router _only_ should have similar effect.

There _IS_ another possibility -- that *YOUR* machine is _both_ of the
computers involved.  <grin>

This can 'theoretically' happen if it connects _both_ by the wireless, AND
via the wi-fi, at the same time, to the same router.

There is a setting "somewhere" -- I forget where, and it's not showing
up in a casual search -- that disables one of the interfaces (the Ethernet
or the wi-fi one) when the other one is in use.  In a situation where you
might be using a cable  _and_ within range of the wi fi from the same router,
it is a -really- good idea to get this 'either/or' setting turned on.

*OR*, you can 'manually' disable the Wi-Fi connection on the "network
connections" panel, when using the Ethernet cable.   You *do* have to
remember to re-enable it before the wireless will work elsewhere, though.

Open a command prompt and type (without the quotes) "ipconfig /release" and
hit "Enter" and then type "ipconfig /renew" and hit "Enter". This should get
you a new ip address from whatever device on your network hands them out
thereby resolving any potential conflicts

As for your infrequent reboots, I'd recommend you reconsider that position.
Windows (which I assume your using) is good at creating temp files as needed
but not so good at removing them when no longer needed except when
restarting. Always your choice, though.

saw the other notes and concur except:

If you are running XP and have the local area connection Icon in the
System Tray (lower right corner for me) you can right click that and
select "repair".  That will do the lease release  and renew cycle
automatically as well as flush a few other bufffers for you.

I read some of the replies...not all...so this may have already been
covered.

Robert is the closest.  Pay attention to his responses.

Let's start at the beginning.  Your problem may be caused by one of several
issues.  It's best to understand how it should work so you can properly
troubleshoot and then post data we can use to help more efficiently.

When you boot the computer you are booting as a workstation on a network.
Some other computer has to be the server.  Your workstation can also be a
server.  Servers are not necessarily what you consider to be a computer.
Your router is a server.  The ISP has servers...mail, DHCP, HTTP and so
forth.  Printers can be servers to serve up print services.  And each
service available on a network can have it's own server for that service.
And each can be a workstation too.

A DHCP (Dynamic Host Configuration Protocol) server is used on networks to
issue a lease on an IP address that is within it's range of addresses.  When
set up properly you will tell the DHCP server what IP addresses are
available as a range of available IPs (the pool).  In a large network I
would do this by creating a subnet mask.  We won't get into subnet masking
for your purposes though.  You have a small network.  You need maybe 5
IPs...one for you, one for the wife, one for the printer and a couple for
other gadgets I have not thought of.  Remember that the router that acts as
the DHCP server also needs its own IP...that's four now.

The DHCP needs to know the gateway used by computers on the network also.
The gateway is how it reaches the internet.  And this is where a firewall
can create problems.  Your modem needs an IP address...but that address is
usually provided by the ISP's own DHCP server.  That becomes like a static
IP address for your internal network (although it is usually not
static...the ISP provides it as a dynamic lease, but I just think of it like
a static for internal purposes). Remember that leases expire.  The
expiration time is defined on the DHCP server.  If you log in again before
it expires then you get the same IP number as you had before.  If it's been
a while you may get a new address.  For security purposes you want the lease
to expire rapidly.  For ease of use you want a very long lease.  Someone has
to make a compromise decision.  Out of the box, routers made for consumers
are usually set to have a long lease period.  On my work servers I set the
lease to expire every 1 minute.  It has a cost, but for my security reason I
pay that cost.  At home I leave the expiration as set by the manufacturer
and I think it is something like a week.  I don't care if my neighbors hack
my system and get a hold of my porn.

Robert suggested using static IPs on your internal network.  This can work
to your advantage.  But it requires more management.  If a friend stops by
to visit and asks permission to log onto your wifi then you have to help him
set up his network dialogs.  Then he goes home and it doesn't work on his
network.  Or...you have your computer working nicely on your network then
you run down to Starbucks to get a cup of nasty coffee and decide to check
your mail...you can't get connected.  You have to reset your network
dialogs.  And then remember to set them back to static when you go home.  I
know this from experience.  We use statics at work.  I travel a lot on
business and try to connect to other people's networks.  It's a hassle.  But
it's not unmanageable.

And the real kicker is if you set the DHCP properly it will fix your problem
and at a lower cost.

DHCP keeps a log of the IP addresses it has assigned on the network.  It
keeps this in a table that stores the MAC address of the machine and the IP
assigned to it.  I think this is called a Network Address Translation table
(NAT).  I may be wrong about that.  The table is updated according to new
leases issued and old leases expiring.  When you log in and your lease has
not expired your machine wants the same lease it had before.  But the server
has already assigned that lease somewhere else.  But how?  It's supposed to
keep track of these things.  The problem may come up because there are two
servers on the network issuing leases.  A true network server would see this
problem and log an error so we can trouble shoot.  The error may tell you it
noticed two computers trying to act as the server and has released authority
to the other server.  But most routers that cost less than 2 grand are not
capable of managing that level of authority so you have to do it.

I know that my own system at home has two routers on the network.  I asked
the phone company to send me a DSL modem that does not act as a DHCP server.
It cost 20 bucks less.  They sent me the more expensive one because they
were sure I did not know what I was doing.  Why would I want something less
capable?  LOL  I explained to them that I already have a wireless router and
did not need their wireless router.  Not because I did not want the higher
level of service, but because I knew two routers on the same network would
cause a problem.

I was able to shut down DHCP on the phone company's modem and just use my
own router (which is way more secure).  But now I have to assign gateways
for both routers which are different.  On the wireless the gateway is the
wireless router.  But that router has a different gateway...the phone
company's router.

If your workstation uses a firewall it becomes another level of routing to
keep track of.  The DHCP server has to know where the internet is and where
each workstation is.  It translates the traffic through the NAT table to
find each node on the network.  A firewall is designed to keep all that
information secret.  If it hides the address from the DHCP server and the
DHCP latter assigns the same address to another node on the network it won't
be able to keep the NAT table straight.  Traffic becomes jumbled.  But it
would not generate an error that the address is already in use...not if it
can't find the address in the first place because the firewall hides it.
But...the firewall has to keep it's own NAT table so it can pass legitimate
packets, right?  So the firewall may have a lease from one DHCP server and
create its own lease for the other side of the network adapter.  In this way
your computer actually ends up with two IPs for one network adapter.
Firewalls can be a software app on your computer or it can be an appliance
on your network.  I use both.  On my appliance it is set up as I described
above.  One IP address collects all the packets and routes it to the other
IP address which sends the packets along to the nodes on the network.  I
just can't see how a conflict could happen unless I use the same network
subnet masks on both sides...which would defeat the purpose of the firewall.

OK...I am getting way too technical now.  If any of this rings a bell and
leads to more data we can use to troubleshoot...post it up and we will get
more specific and less technical from there.

Nate

I assume your router is DHCP and assigning addresses.  If you use
cable (wired) and then disconnect and go wireless, your PC may be
confused that there is another IP address on the network.  Either
reboot the PC or open a cmd prompt and type "ipconfig /renew"

Joe