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MaynardKrebs
We did it. We heaved Steve. Yipee.
Premium Member
join:2009-06-17

MaynardKrebs to Domane

Premium Member

to Domane

Re: Identity by IP.

Power your modem off for 60 minutes.
This should be more than enough time to get a new IP from even on the least busy TWC upstream routers. Cable routers tend to hold the IP/physical line association a bit longer than do the telco's dynamic xDSL addresses assignments.

DocDrew
How can I help?
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join:2009-01-28
SoCal
Ubee E31U2V1
Technicolor TC4400
Linksys EA6900

4 edits

DocDrew

Premium Member

said by MaynardKrebs:

Power your modem off for 60 minutes.
This should be more than enough time to get a new IP from even on the least busy TWC upstream routers. Cable routers tend to hold the IP/physical line association a bit longer than do the telco's dynamic xDSL addresses assignments.

Yeah... that usually doesn't work since the lease time is usually many hours. The device MAC address is linked to the IP lease in the DHCP server records, so the same MAC address will be issued the same IP address as long as it's available. The currently assigned IP won't be reissued to another user until the lease expires AND all other IPs in that DHCP scope are issued. CSRs can't change an IP either, they have no access to the DHCP servers.

Many cable users hang on to the same IP for weeks and months even if they power off the modem every night. Major equipment changes or large outages are frequently the only reason it changes without end user intervention.

The only sure way to get a new public IP on demand is to change MAC addresses of the device requesting the public IP, power cycle the modem, and have the device request a new lease.... but that won't work if it's a combo router modem.

This is the way the majority of major north American cable ISPs operate.

Domane
Premium Member
join:2013-04-18

Domane to MaynardKrebs

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to MaynardKrebs
The way TWC system is set up that services me I cannot change the dynamic IP. All ready have tried all the methods and TWC has confirmed that no action from my end can change it. It will change when TWC reassigns IPs per whatever criteria for IP changes happens at their end.

StuartMW
Premium Member
join:2000-08-06

StuartMW

Premium Member

Hmm, I guess they must use static allocation (assign IP by MAC) which must be a real pain to maintain.

DocDrew
How can I help?
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join:2009-01-28
SoCal
Ubee E31U2V1
Technicolor TC4400
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DocDrew

Premium Member

said by StuartMW:

Hmm, I guess they must use static allocation (assign IP by MAC) which must be a real pain to maintain.

It's all automatically maintained by the DHCP servers. No real pain at all. Using your link, it's closer to what they call "automatic allocation".

StuartMW
Premium Member
join:2000-08-06

StuartMW

Premium Member

Doesn't someone have to manually enter the MAC to IP mapping at some point?

I use static allocation on my home network so I don't have to run local DNS.
TheWiseGuy
Dog And Butterfly
MVM
join:2002-07-04
East Stroudsburg, PA

TheWiseGuy to StuartMW

MVM

to StuartMW
I believe most Cable operators use automatic allocation. The IP address is linked to the MAC address of the Consumer Premise Device. In the case of a combo router/modem you would need either access to the router config and be able to clone a new MAC address to change the IP. I do not know if the combos allow that type of access.
said by your wiki link :

automatic allocation: The DHCP server permanently assigns a free IP address to a requesting client from the range defined by the administrator. This is like dynamic allocation, but the DHCP server keeps a table of past IP address assignments, so that it can preferentially assign to a client the same IP address that the client previously had.


DocDrew
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join:2009-01-28
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DocDrew to StuartMW

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to StuartMW
said by StuartMW:

Doesn't someone have to manually enter the MAC to IP mapping at some point?

I use static allocation on my home network so I don't have to run local DNS.

Nope. The DHCP server issues the IP from an assigned scope based on CMTS configuration. The DHCP server will place the requesting device MAC in a database with the IP issued. It'll only reuse the IP if the lease is expired AND there are no other IPs left in the scope.

A major outage taking down modems past their lease times, odd DHCP database problem, CMTS config change, or forced database change by an Engineer with access are some of the few ways the IPs will change from the provider side.

Otherwise the end user can change MAC addresses, reset the modem, and request a new lease. A release/renew cycle or leaving the modem off for a few minutes, hours, or days (depending on IP lease churn) won't clear the DHCP server records so the same IP will be reissued.

Domane
Premium Member
join:2013-04-18

Domane

Premium Member

said by DocDrew:

The DHCP server issues the IP from an assigned scope based on CMTS configuration. The DHCP server will place the requesting device MAC in a database with the IP issued. It'll only reuse the IP if the lease is expired AND there are no other IPs left in the scope.

A major outage taking down modems past their lease times, odd DHCP database problem, CMTS config change, or forced database change by an Engineer with access are some of the few ways the IPs will change from the provider side.

Otherwise the end user can change MAC addresses, reset the modem, and request a new lease. A release/renew cycle or leaving the modem off for a few minutes, hours, or days (depending on IP lease churn) won't clear the DHCP server records so the same IP will be reissued.

That's it. The last paragraph is especially applicable or relevant to the average user. Believe me, I know.

kontos
xyzzy
join:2001-10-04
West Henrietta, NY

kontos to Domane

Member

to Domane
said by Domane:

The way TWC system is set up that services me I cannot change the dynamic IP. All ready have tried all the methods and TWC has confirmed that no action from my end can change it.

It is doubtful that that is correct. Change the reported MAC address of the device that is directly connected to your modem, and then power-cycle the modem, and you should have a new IP address. If your PC is what is connected to the modem, you can probably change the hardware address in the driver config for you network card. A router will have at least a 'clone' option in the WAN setup area.

Domane
Premium Member
join:2013-04-18

Domane

Premium Member

Redacted.

Snowy
Lock him up!!!
Premium Member
join:2003-04-05
Kailua, HI

Snowy

Premium Member

said by Domane:

You don't know my hardware setup.

Is this a game of guess?
I had previously asked what service you were running that was communicating with the 2nd party.
It's not secret stuff -