How can I force Vista to get new IP on wireless network change

[Guest]

[Rock Xtreme laptop with Vista HP] My wifi connection is set to use DHCP if
available but has a (manual) alternate fixed address set up (which I assumes
was to be used when DHCP is not available)

When I go to my regular cafe, it connects correctly obtaining an IP address
from their Netgear router... when I come home Vista reconnects to my home
network(also a Netgear router) but since this router does not use DHCP it
SHOULD go back to the alternate address... but it doesn't, and I usually get
an IP address conflict warning (as the cafe seems to give me the IP
192.168.1.x address that is my home router's address)

Is this a general Vista problem - that on network change IP addresses are
not renewed - or is there some setting I have overlooked that will force it
to get a new address? (without using IPCONFIG /renew... why should I have to
do all that!)

Thanks!

PS IPv6 is turned OFF on all network connections

 

[Robert L \(MS-MVP\)]

Post the result of ipconfig /all here when connecting to home network. Also
if you use static at home, ipconfig /renew doesn't work. Check this post to
make sure you setup it correctly.

How to: assign multiple static IPs ...You have two ways to assign multiple
IP addresses on Vista. ... you enable DHCP and select Alternative
Configuration. then add static IP address. ...
www.chicagotech.net/netforums/viewtopic.php?t=496


--
Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on
http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on
http://www.HowToNetworking.com

 

[Guest]

Post the result of ipconfig /all here when connecting to home network.

Have taken a snapshot at home, will take one at the cafe later and again
when I come home again

if you use static at home, ipconfig /renew doesn't work.

Ah! It means "renew" in the sense of GET a new DHCP IP! There's no trusting
technical terminology sometimes, I thought it would do that or reload IP
manual settings as appropriate. Thanks for letting me know.

[Comment becomes - "without 'repairing' or disabling/re-enabling the

Check this post to make sure you setup it correctly.
www.chicagotech.net/netforums/viewtopic.php?t=496

I think I'm set up OK but I checked it anyway, only to find that I don't
understand what it is saying: DHCP is enabled (TCP/IPv4...
Properties...General "Obtain an IP address automatically" checked; Advanced
tab shows DHCP enabled) but no option for adding further IP addresses (all
buttons greyed); Alternate Configuration is "User Configured". No idea how to
set multiple static addresses, but I don't need that at the moment.

BTW - the underlying Q is: when Vista switches networks why doesn't it get a
new IP address - or at the very least check the settings and IF there is a
"conflict" do the sensible thing? [If the adapter has an IP address on a
network without DHCP and that IP address is not the Alternate.... User
Configured setting then it is clearly wrong]

Thanks for the help so far...

 

[Joe Guidera]

The alternate user address is only assigned after the DHCP request fails.
In other words, you can determine the "fail" address that is issued. Vista
does request a new address when the network connection changes (assuming you
have that network interface set to request via DHCP). Bear in mind if you
go to sleep while in a location that provides a DHCP issued address and then
"wake up" in another location, it can take a while (I've seen it take about
30 seconds or more) before Vista gives up on the old profile and tries
searching for a new one (and thus obtains a new address).

Not that it should be problematic, but is there any reason why you aren't
using DHCP at home as well?

Joe

Post the result of ipconfig /all here when connecting to home network.

Have taken a snapshot at home, will take one at the cafe later and again
when I come home again

if you use static at home, ipconfig /renew doesn't work.

Ah! It means "renew" in the sense of GET a new DHCP IP! There's no
trusting
technical terminology sometimes, I thought it would do that or reload IP
manual settings as appropriate. Thanks for letting me know.

[Comment becomes - "without 'repairing' or disabling/re-enabling the

Check this post to make sure you setup it correctly.
www.chicagotech.net/netforums/viewtopic.php?t=496

I think I'm set up OK but I checked it anyway, only to find that I don't
understand what it is saying: DHCP is enabled (TCP/IPv4...
Properties...General "Obtain an IP address automatically" checked;
Advanced
tab shows DHCP enabled) but no option for adding further IP addresses (all
buttons greyed); Alternate Configuration is "User Configured". No idea how
to
set multiple static addresses, but I don't need that at the moment.

BTW - the underlying Q is: when Vista switches networks why doesn't it get
a
new IP address - or at the very least check the settings and IF there is a
"conflict" do the sensible thing? [If the adapter has an IP address on a
network without DHCP and that IP address is not the Alternate.... User
Configured setting then it is clearly wrong]

Thanks for the help so far...

 

[Guest]

OK - a bit later than planned but here are some IPCONFIG results (at the
bottom after the comments) - the key thing to note is that the IP address
appears as "(preferred)" when that is NOT the alternate setting established...

Thanks for the input folks...

The alternate user address is only assigned after the DHCP request fails.
In other words, you can determine the "fail" address that is issued. Vista
does request a new address when the network connection changes (assuming you
have that network interface set to request via DHCP). Bear in mind if you
go to sleep while in a location that provides a DHCP issued address and then
"wake up" in another location, it can take a while (I've seen it take about
30 seconds or more) before Vista gives up on the old profile and tries
searching for a new one (and thus obtains a new address).

Which is basically my point: it *should* detect a network change and
invalidate the previous IP address immediately, but it doesn't - hence IP
conflicts. Yes, I knew that the alternate was the "fail" result, which is a
bit annoying in the first place - but there you go.

Not that it should be problematic, but is there any reason why you aren't
using DHCP at home as well?

Only that I wanted fixed IP addresses so that port forwarding on the LINUX
based router would be guaranteed to work... and there were several potential
DHCP servers and I could never find out how to configure a system so with
more than one DHCP server (one couldn't guarantee which devices would be on,
so it was never clear that there would be a DHCP server or how to work with
more than one, so it was easier just to give them all fixed IP addresses)

Here's the IP config data... (dummy MAC addresses... last thing I'm going to
do with a locked down system is publish the permitted MAC addresses!)

IP Config 11 Oct AM - Home Network

Windows IP Configuration

Host Name . . . . . . . . . . . . : MyHost
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Wireless LAN adapter Wireless Network Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) PRO/Wireless 3945ABG Network
Connection
Physical Address. . . . . . . . . : AA-BB-CC-DD-EE-FF
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 192.168.1.80(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 192.168.1.1
NetBIOS over Tcpip. . . . . . . . : Enabled

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek RTL8169/8110 Family PCI
Gigabit Ethernet NIC (NDIS 6.0)
Physical Address. . . . . . . . . : AA-BB-CC-DD-EE-FF
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 192.168.2.1(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : 10 October 2007 03:14:28
Lease Expires . . . . . . . . . . : 20 October 2007 09:37:11
Default Gateway . . . . . . . . . : 192.168.2.254
DHCP Server . . . . . . . . . . . : 192.168.2.254
DNS Servers . . . . . . . . . . . : 192.168.1.1
NetBIOS over Tcpip. . . . . . . . : Enabled

Cafe Network

Windows IP Configuration

Host Name . . . . . . . . . . . . : Berossus
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Wireless LAN adapter Wireless Network Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) PRO/Wireless 3945ABG Network
Connection
Physical Address. . . . . . . . . : AA-BB-CC-DD-EE-FF
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 192.168.1.12(Preferred) [NO IT ISN'T!]
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : 11 October 2007 11:29:37
Lease Expires . . . . . . . . . . : 12 October 2007 11:29:37
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 192.168.1.1
NetBIOS over Tcpip. . . . . . . . : Enabled

Ethernet adapter Local Area Connection:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek RTL8169/8110 Family PCI
Gigabit Ethernet NIC (NDIS 6.0)
Physical Address. . . . . . . . . : AA-BB-CC-DD-EE-FF
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes