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Dynamic IP Address change from ISP

I have a client that setup content filtering for a static IP not realizing that he was being assigned a public IP dynamically.  Apparentely, when the IP was assigned to another user, they started getting blocked to sites they were used to visiting.

My question is; how often does a dynamic IP address change for a user?  I'm sure this can change per ISP settings, but what is a normal scenario?
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lobo797
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lobo797
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3 Solutions
 
MrN1c3Commented:
When a client is leased an IP address, it will be given a lease expiry date/time.  That time is dependent on how the DHCP scope was setup on the DHCP Server.  You could always reserve the IP address for that client, or request a static one.
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lobo797Author Commented:
So, I quess my question is, could the IP address change 8-10 in a 24 hour period?  Can the address change if the lease expires during an online session?
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bcbigbCommented:
It certainly could change that often (though it's highly unlikely), but it's almost always in 24 hour increments. Some ISPs I have seen go as low as 1 day leases (especially if they're oversubscribing their pool of public IP addresses) but most stay at 5 or 7 day leases in my experience.
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bcbigbCommented:
The address is automatically set to renew when the lease is up, but yes, the DHCP server can give it out or restrict access to it or whatever else it is set to do at the expiration time. An administrator can also remove the lease and make the IP address go back into the available pool again so someone else will get it (potentially conflicting with you!). This is highly unlikely in an ISP's scenario, as managing individual IPs would be massively time-consuming... but you never know. The rule of thumb is: he who owns the server makes the rules.
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MrN1c3Commented:
on one of the clients (assuming its running windows)

type "ipconfig /all" at the command prompt

This will show you what time the client was issues a lease and when it expires, which is the lease time.

Halfway through the lease, the client will request the same IP address
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Rick_O_ShayCommented:
If it is a public address assigned by an ISP it can change especially if the device goes away and then comes back. The ISPs are reusing those addresses where ever there is an active device and if you give it up it will be handed out somewhere else.
If the device is always up then the address will be controlled by the ISP's DHCP settings for lease time.
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lobo797Author Commented:
MrN1cs,
The IP in question is on the public side of the wireless radio/router serving my client internet access.  ipconfig will only tell me what the lan dhcp is giving, correct?

I figured as much about the lease changing, but this client received about 8 emails in a 24 hour period that were forwarded from users that were getting blocked per the settings on the IP address in question.  I thought that seemed a little much.
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lobo797Author Commented:
Rick,
What you are saying is that with a wireless radio, that can fall offline for any number of reasons, the public IP could indeed change several times a day!  Interesting...
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Rick_O_ShayCommented:
You are correct about seeing the lease time with ipconfig only on the PCs on the LAN. There may be a status field in the router for the WAN side address expiration info.

I am a bit puzzled about how a content filter on his router or proxy could impact anyone else though. Isn't that just filtering what his inside devices can see on the Internet?
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Rick_O_ShayCommented:
Relating to the comment about dropping off, it will happen to wired or wireless connections on the public side if they are DHCP assigned. Is the public side of this router wireless? I suspect the carriers are even quicker to change things on a wireless network due to its mobile nature.
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lobo797Author Commented:
Rick,
The public side of the router is wireless, which is an issue all of it's own :(

The content filtering that was setup was through OpenDNS which I would take to reside on their servers.  If the settings were put on a single IP address, guess what happens when someone else gets that address!  They get angry as we seen from the emails!
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Rick_O_ShayCommented:
OK I see now. Thanks for the update.
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lobo797Author Commented:
Thanks for the help!
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