| reply to workablob
Re: [Connectivity] Linksys Router assigns wrong IP address
Wireshark Dump |
I don't know where the post went that had my Wireshark dump, but here is a screenshot of that as well.
As to why I have not replaced the cable modem, I thought I explained that Comcast says its not their problem, its a router problem which I think we all can agree. |
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| reply to jaynick
You beat me to it....Make sure it's a straight through. |
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| reply to jaynick
Yes, I have replaced the ethernet cable in the past to no avail.
And no, it has nothing to do with a bad device. It started with a Linksys Phone adaptor in the beginning. Now I have added two additional devices, the Magicjack phone adaptor, and the Apple TV, all which get wrong IP addresses.
The majority of my network uses fixed IP addresses except for the wireless devices such as my iPhone, iPad, etc. Those all get the right IP addresses assigned by the router.
I suppose I can try going back to Comcast and try to get another cable modem. Maybe that is worth a shot. |
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| reply to Wayne99021
Ethernet Cable |
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 jaynicklit upPremium
join:2001-02-06
Sterling Heights, MI
kudos:2 | reply to flashsolutio
You need to get past the idea of disabling dhcp in the modem. It can't be done by you and comcast won't. gar187er said that twice. |
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jaynicklit upPremium
join:2001-02-06
Sterling Heights, MI
kudos:2 Reviews:
 ·Comcast
2 edits | reply to flashsolutio
What IP's did you assign the 2 devices you are having trouble with? Are they from the router's block or modems ? I saw a previous screenshot where they looked to be from the modem's. I saw you had the router's IP as 192.168.100.1, I would think it should be 192.168.1.1 and devices should be 192.168.1.2 thru 254. And are you sure the router is configured to be the dhcp server? I am not trying to be disparaging or anything but from personal experience, I know sometimes one can get frustrated with computer or networking issues and sometimes miss a simple setting. |
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| reply to flashsolutio
I know you have done this, but lets make sure one more time.
Just to verify, perform the following.
»www6.nohold.net/Cisco2/ukp.aspx?···eid=3686 |
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biomeshPremium
join:2006-07-08
Tomball, TX | Do you have a Pace device connected anywhere on your network? (cable box/gateway/etc) |
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jaynicklit upPremium
join:2001-02-06
Sterling Heights, MI
kudos:2 Reviews:
·Comcast
2 edits | reply to sabretooth
The router's mac should be sufficient. mac cloning should not be necessary.  The Op has either an improperly configured router or a defective one. Since he stated he has that issue with 2 routers, my money is on some configuration issue. |
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 plencnerbPremium
join:2000-09-25
Elgin, IL
kudos:2 | reply to jaynick
said by jaynick:What IP's did you assign the 2 devices you are having trouble with? Are they from the router's block or modems ?
I was actually wondering the same thing. You said in your first post that the router would assign IP's in the range of 192.168.1.100 thru 192.168.1.150. If you 2 static IP's are in that range, that might be causing a problem, in the event your router tries to give that IP out, it may fail or time out. During that time period, your modem could then kick out an IP in response to the IP request from your device.
Knowing that you have the range set high (normally, the range would be 192.168.1.2 to 192.168.1.254), I am thinking you did that so that you could assign your static IP's in the range of 192.168.1.2 to 192.168.1.99, and use the range of .100 to .150 for your DHCP IP's.
Just wanted to verify that as well. Again, you may have said that, but just something else to check.
--Brian
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--Brian Plencner
E-Mail: CoasterBrian72Cancer@gmail.com
Note: Kill Cancer to Reply via e-mail |
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| reply to flashsolutio
So this happens when you lose power and everything reboots at the same time?
The MTA's/Modem will act as a DHCP server when there is no connection to the CMTS (Cable Co)
So when it first comes back on, it may give out 192 addresses before it locks. Sounds like the switch portion of the router is passing them through to the devices before the router portion comes back up.
Cant you just set the device addresses to static? Or did I miss a post?
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"I'm against picketing, but I don't know how to show it" - Mitch Hedberg |
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biomeshPremium
join:2006-07-08
Tomball, TX | The device with MAC address ending with 8E:97:0A is the device with the IP address 192.168.100.1. Can you confirm if this is the MAC address of your cable modem or what device is it? |
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DavesnothereNo-BHELL-ity DOES have its Advantages
join:2009-06-15
START&Cogeco
kudos:6
4 edits | reply to workablob
said by workablob:....It is textbook case of two DHCP servers on the same network fighting it out....
I agree with what you say is happening symptomatically, but not necessarily with the reason (i.e. the wiring is fine).
My router is also a Linksys (WRT54GL, factory firmware), and I'm on Cogeco Cable in Canada, on a Cisco something-3000 modem.
Here are the issues, as I see them :
When on Cable service, a subscriber's router usually needs to be set to get its own external IP address from SOME device upstream, so IT needs to be set to SEEK a DHCP.
Whether the device providing the router with that IP is the subscriber's modem, or something else further upstream - that will depend upon how THE ISP (Comcast) runs their network, and I do not know the specifics on that.
If the router's external IP comes from a DHCP server within the Modem, then even if you COULD disable that server, you may not be wise to, as you would then be forced to specify a STATIC external IP for your router in order for the router and modem to 'SEE' each other, and I'm not sure that making such a setting is even possible (can only set the Internal IP of the router, for the LAN side of things ?).
Some routers DO allow more communication with upstream devices than others (another example is logging into the upstream device's config screens from a PC below the lower device), so the behaviour of the router may well be by design, though that would be inconvenient for sure.
I personally find DHCP to be an PITA for a variety of reasons, and as such, I use STATIC IPs within my LAN for any permanent devices, and only let guest devices use DHCP, so I have not encountered your sort of issue so far.
Your partial workaround might be best, except for the MagicJack, which I will not use anyway, as they do not offer small town phone numbers in Canada, and neither any existing phone number porting, last time I checked.
Unfortunately, MY scenario may not satisfy YOUR needs.
Borrowing other routers might be worth a try, and then recreating the situation in which the malfunction happens.
Fancier router firmware (such as Tomato, DD-WRT, Open-WRT) sometimes lets one set exactly what types of data are passed/blocked between devices up and downstream of it.
Many Linksys routers support alt f/w, but I do not know the particulars.
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We have only 2 things about which to worry :
(1) That things may never get back to normal
(2) That they already HAVE !
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| reply to biomesh
said by biomesh:The device with MAC address ending with 8E:97:0A is the device with the IP address 192.168.100.1. Can you confirm if this is the MAC address of your cable modem or what device is it?
That looks like a cable tv box.
Do you have an ethernet cord plugged into any cable boxes? Double check.
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"I'm against picketing, but I don't know how to show it" - Mitch Hedberg |
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Reviews:
·Comcast
| reply to Davesnothere
The Cable Modem can be in NAT mode or Bridged, Usually they are in NAT mode and need to be put into Bridged mode. This is not the case for my comcast modem but ATT (SBC) and others do it a lot.
I have spent a good chunk of my time on the phone with sbcglobal support getting them to understand what I needed the modem to do.
If some clients get the IP from the Linksys and others from the modem both DHCP servers are answering requests on the same network which is BAD.
Dave |
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jaynicklit upPremium
join:2001-02-06
Sterling Heights, MI
kudos:2 | You can't do that with cable modems! Unless you have an SMC business modem, otherwise they are a dumb bridge. |
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| I should have said DSL modem which is what I was thinking of.
Either way, it still sounds like two DHCP server on the same network.
Dave |
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jaynicklit upPremium
join:2001-02-06
Sterling Heights, MI
kudos:2 Reviews:
·Comcast
| said by workablob:I should have said DSL modem which is what I was thinking of.
Either way, it still sounds like two DHCP server on the same network.
Dave
No worries bud!  |
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DavesnothereNo-BHELL-ity DOES have its Advantages
join:2009-06-15
START&Cogeco
kudos:6
2 edits | reply to workablob
said by workablob:The Cable Modem can be in NAT mode or Bridged, Usually they are in NAT mode and need to be put into Bridged mode. This is not the case for my comcast modem but ATT (SBC) and others do it a lot.
I have spent a good chunk of my time on the phone with sbcglobal support getting them to understand what I needed the modem to do.
If some clients get the IP from the Linksys and others from the modem both DHCP servers are answering requests on the same network, which is BAD.
I completely agree with your bottom line.
My experience is more with DSL than with Cable, where it seems that folks have very frequently had issues due to F-N combo DSL modems with only a single Ethernet output, and these folks are unaware of a 2nd router lurking within the modem when they try to add a standalone router.
At that point, all BHell (Canadian ISP put-down humour) breaks loose ! 
I was not aware until today that Cable subscribers also can have weird interactions between modems and routers, but.... 
It could be that running my LAN devices with local STATIC IPs whenever possible/practical has helped me avoid much of the BS, a plan which I began for other reasons back when I was on DSL.
--
We have only 2 things about which to worry :
(1) That things may never get back to normal
(2) That they already HAVE !
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jaynicklit upPremium
join:2001-02-06
Sterling Heights, MI
kudos:2 | reply to flashsolutio
BTW, what happened to the OP? |
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