# How can I tell what IP address my router is assigning various devices?



## St!nkf!nger (Aug 24, 2003)

I have a Linksys RT31P2 router which seems to be acting funny. What happens is it randomly seems to assign my pc different IP addresses. I have it set to hand out a max of 50 addresses (100 - 149) and my pc has always been .100, but for some reason yesterday it assigned it .134. It's really annoying because several of my programs need ports forwarded to work and having to change them in my router is tedious and unnecessary. Anyone know why this is happening?


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## Couriant (Mar 26, 2002)

It's releasing and renewing the IP address. It's normal. If you need the machine to have a 'static' IP address, then set a Static IP address for the MAC address of your machine in the Static DHCP part of your router configuration.


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## St!nkf!nger (Aug 24, 2003)

Tidus4Yuna said:


> It's releasing and renewing the IP address. It's normal. If you need the machine to have a 'static' IP address, then set a Static IP address for the MAC address of your machine in the Static DHCP part of your router configuration.


Sounds good, now if only my router supported that. I guess I can set the lease to more than 0 days, that should work too, correct?


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## NiteHawk (Mar 9, 2003)

First off, why 50 addresses? Chances are this is a 4 port router. The extra 46 ports are just holes in your network that someone could slip into. I would suggest 4 or 5 max.

The way that DHCP works is that it assigns the _lowest_ available address to the first machine that it senses (read first machine that is booted up). The next machine gets the next lowest available address.

IF you are getting 192.168.1.134 I would click Start > Run and type in *cmd*, once you are at the command prompt (aka DOS screen) type in *netstat -a* to see who all is connected to your network.

Next, I would set each PC to it's own Static IP address. IF you don't know how to setup a "hard coded" IP address let us know and someone will walk you thru it.

You didn't mention if this is a wired or wireless network.

BTW, MAC ID was mentioned, MAC filtering works, but not as well as most people think.


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## Couriant (Mar 26, 2002)

St!nkf!nger said:


> Sounds good, now if only my router supported that. I guess I can set the lease to more than 0 days, that should work too, correct?


I would be shocked if your router didn't support it. It's pretty much a timesaver instead of hardcoding the IP address.


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## Courtneyc (Dec 7, 2003)

Actually, it doesn't matter if your router supports it or not. if you have your range set between 100 and 149, but you set up your workstation with an IP address of .10, your system will still work fine. 

The range you assign is for the DHCP server in the router, it has nothing to do with the router itself. For example, if you set your router to not assign any ports whatsoever, and you manually assign addresses to your devices, they will still work. 

Just make sure you assign the right set of octets, the right subnet, and the right gateway (the router itself). The router will still handle the DNS services.

courtney


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## StumpedTechy (Jul 7, 2004)

Here is what I do and it works wonderfully - From a working PC with DHCP type in IPCONFIG /all and put all that information into the TCP/IP properties of your network adapter. Then change the LAST octet of the IP address to something that 1) isn't the ip of the router and 2) is outside of any DHCP range you have setup. This will ensure you have no conflicts with someone who comes and plugs in at a later time. This also ensures it never changes and that any ports will still be open.

I still wonder why you can't forward ports based on MAC addresses I mean you can block wireless with that why not use the same technology to map ports to a physical adapter rather than an IP that may or may not change.


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