Teacher
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32 Messages
certain IP addresses blocked on one computer
Hi,
I thought I was having the same problem as GregDO, but it appears mine is different, as my IP address does not start with 172.
I can connect to everything via my ATT router except websites on both my GoDaddy hosting accounts.
Earlier I had remedied this by switching to Google's DNS server at 8.8.8. That worked for several weeks but stopped working yesterday. I also tried changing my router to make my main work machine a DMZ, also to no avail.
This morning I tried a factory reset on my router, after which I had access to websites on these two IP addresses for about 15 minutes before they were blocked again.
I can connect to these addresses with no problem when I am using my mobile hotspot.
I can also connect using a different computer with identical settings.
I interact with these IP addresses heavily, as I am a web developer. I suspect that they are being blocked by some kind of firewall, either on the router or upstream at ATT.
Because the problem reappeared shortly after I reset the router, I am concerned that the problem may lie upstream from it - i.e. ATT is assuming some sort of exploit is occurring and is explicitly blocking traffic between the mac address of the affected computer and the two IP addresses that I most want to connect to.
I have a technician coming out to look at the problem this afternoon, but am worried that he or she will not be able to resolve the situation.
I'm wondering if anyone in the community has insight into this problem.
Saill
sailll
Teacher
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32 Messages
10 years ago
Yeah - saw the table pop up. Sorry about all the extra posting. Let me know if you think of anything else I should have a look at.
Meanwhile my workaround is keeping me connected and happy today.
Saill
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sailll
Teacher
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32 Messages
10 years ago
Quick update.
Had a visit from another very knowledgeable and curious technician. He observed the problem, and was mystified.
We did however do some further testing by connecting his iPad to my RG. His iPad's ability to connect was unaffected by whether either of my Linux machines was "sitting on" an IP address. After he left I turned on my Windows 8 tablet and saw the same result.
I also discovered that whichever of my two Linux machines is the last to boot is the one which loses the abilitly to connect to an IP address whose TCP state on the other machine is Established or Time Wait.
So this seems to be a Linux (OpenSUSE 13.1/KDE) thing, or more specifically some kind of interaction between my two Linux machines connected to the internet via the ATT RG. The two machines have no conflicts when both are connected through my ATT/Android/HTC One mobile hotspot.
Given all that, I will mark this issue resolved. It doesn't really affect me, now that I understand the mechanism, since no one ever actually uses both of the Linux machines on my network at the same time!
Saill
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JefferMC
ACE - Expert
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35.5K Messages
10 years ago
Do the two machines report a name when they do their DHCP request to the RG? Would they provide the same name?
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sailll
Teacher
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32 Messages
10 years ago
@JefferMC - They have different host names, and when their IP addresses were assigned via DHCP the RG listed them by these host names. They both now have static IP addresses, which causes the RG to list them as "unknown.MACaddress", like unknownFCF8AEC782A6.
The issue is the same whether the IP addresses are assigned or static. I'm leaving them static now so they won't get reassigned.
And yes I'm using different IP addresses - that's the first thing the technician checked!
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ATTU-verseCare
Community Support
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6.7K Messages
10 years ago
Hi @sailll ,
Thank you for providing all that information. I am still at a lost on what happens. I thought of several things, but it is always discredited when I remember the fact that you cannot make a connection with a telnet connection to the site on port 80 with one of the machines, so it means that the issue is going in the outbound direction. My only thoughts is that an ack/nack is being intercepted by the other host machine causing a failure to connect. Either way, I am happy you were able to find a workaround. I really wish I could come up with the specific answer to your issue, but without having the ability to do a full packet trace, I could not really say what is causing the problem.
-David T
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sailll
Teacher
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32 Messages
10 years ago
@ATTU-verseCare thanks for checking in. I'm at a loss as to the exact mechanism as well, but very relieved that there is a simple workaround.
Maybe this will help someone who is having a similar problem!
Saill
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