Can an IP address change whilst on-line?

[ChrisRChamberlain]

Hi all

Have now got a couple of clients requiring support via pcAnywhere whose ASDL service providers generate different IP addresses every time they reboot and logon.

Naive question but am I correct in assuming the IP address will remain constant until such time as the user logs off the connection or reboots?

TIA

FAQ184-2483 - answering getting answered.​

Chris
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[jgideon]

I'm sure someone will give you a more detailed answer, but while it is unlikely, it is possible. DHCP leases are configurable by the machine assigning them... could be one minute, could be one year. On a WindowsXP machine, if you go to a command prompt and enter "ipconfig /all" (without the quotes) one of the entries under the adapter being used will be 'lease obtained' and 'lease expired'--that would give you the 'correct' answer for that particular machine at that particular time. Keep in mind that if the workstation in question is behind a router/firewall, then it may have an 'internal' dhcp lease which isn't directly tied to the one assigned by the ISP.

 

[ChrisRChamberlain]

jgideon

Thanks for your reply.

one of the entries under the adapter being used will be 'lease obtained' and 'lease expired'

Not getting that on my XP Pro SP2 machine.

FAQ184-2483 - answering getting answered.​

Chris
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[DTSMAN]

I use pcanywhere on a daily basis for customer support and that does not happen, then again, I see to it that any machine I am accessing has a static IP for port forwarding reasons. Their routers are setup to obtain from the dsl modem but that has never bumped me out in the middle of a session. I would give static IPs to the host machines.

Bo

Kentucky phone support-
"Mash the Kentrol key and hit scape."

 

[ChrisRChamberlain]

I would give static IPs to the host machines

There is no choice in the matter - if a client elects to use an ISP who does not provide a static IP address then, whilst I can suggest this is not in their best interest, I cannot insist they choose an ISP who does.

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Chris
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[jgideon]

Chris:
Not sure why you're not getting it. He's what mine looks like:

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

G:\Documents and Settings\CLIENT8>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : client8
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : VIA Rhine II Fast Ethernet Adapter
Physical Address. . . . . . . . . : 00-11-5B-01-48-B7
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.1.49
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.41
DNS Servers . . . . . . . . . . . : 192.168.1.1
Lease Obtained. . . . . . . . . . : Sunday, May 14, 2006 2:18:37 AM
Lease Expires . . . . . . . . . . : Wednesday, May 17, 2006 2:18:37 AM

My DHCP server is a box on my network. That server has a table of MAC addresses and IP that goes with said MAC. I'm not sure what it's officially called, but I think of it as 'static dhcp' since theoretcially every machine should get the same IP for every lease renewal.

 

[jgideon]

I had another thought--I have another adatpter that is a PPP connection for our corporate VPN which I wasn't including:

PPP adapter {edited}:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : WAN (PPP/SLIP) Interface
Physical Address. . . . . . . . . : 00-53-45-00-00-00
Dhcp Enabled. . . . . . . . . . . : No
IP Address. . . . . . . . . . . . : 10.20.31.143
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . :


Maybe if it is PPP or PPPoE, then the address is 'permanant' until disconnect?

 

[ChrisRChamberlain]

jgideon

The PCs in question are all 'gateway' machines using ISC to enable the networked PCs access to the internet.

Going to assume the IP address will not change whilst online - I have a utility in place on the user PCs that runs on startup, waits while Windows sorts itself out, and then silently emails the registered organisation, user name and IP address back to myself.

Once again, thanks for your input.

FAQ184-2483 - answering getting answered.​

Chris
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