Slow internet connection every 10 days

Hello, all. What happens is a bit weird so let me explain.

Every 10 to 12 days, usually after noon, internet speed goes almost to a standstill. When I try to go to, let’s say www.google.com on the bottom left of the browser I get messages “… trying to resolve host” etc.
If i try to ping an outside IP address or domain name most of the time i get time outs or if i dont time out the speed is like 1500ms.
If I connect my laptop directly to my Router/Modem then the speed is normal again.
This happens only to computers connected wired or wirelessly to the domain/network.

The topology of the network is as follows.
One Cisco X3000 Modem/Router Connected to an HP Switch providing internet.
Also X3000 is the DHCP provider to the premises. All other computers, printers have manually entered IPs. Also as Gateway they have router’s IP and as DNS1 the server’s IP
One Windows server as Domain Controller and DNS server. In server’s network card as Default Gateway there is the IP (192.168.0.150) of the router and as a DNS1 its own IP (192.168.0.100).

As for the forwarders I have the IP of the providers DNS and Google’s.
And that’s it. I can’t figure out what is wrong with my network. It’s very weird that this happens only once in a while so it’s hard to pinpoint the problem.
I have checked if someone is downloading something big etc. No luck.
Also I have checked with our provider if our DSL line is ok and every time it checks out.

Thank you for the assistance.
Dionisis.
DionisisTAsked:
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giltjrConnect With a Mentor Commented:
I would do more packet captures, 1000 or so packets is not really a lot.

You have a good weekend too.
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giltjrCommented:
Does your ISP provide you with a fixed IP public address or do you get it via DHCP?

How long is the slow down?  A few minutes, a few hours, the whole day?
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DionisisTAuthor Commented:
Static IP and the slowdown lasts about 2 maybe 2 and a half hours.
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giltjrCommented:
Is there a way you can to a packet capture on the HP switch of the port the modem is on?

Sounds almost like somebody is doing a backup every 10 days of of something.
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DionisisTAuthor Commented:
How can I do that? I thought that too. The packet capturing. During the slowdown it would be great if I could see the traffic. There is a piece of hardware that every now and then communicates with a remote location but both user and the engineer responsible for it assured me that this was not the case.
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giltjrCommented:
What model switches do you have?

Are they managed or unmanaged?
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DionisisTAuthor Commented:
Sorry but I can't answer that right now. But i'm pretty sure its manageable. I'll return tomorrow morning for the model. If it is manageable I can monitor traffic right?
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tmoore1962Commented:
If you go into DNS console on server and restart the DNS server service does that remedy the issue or does internet remain slow?  If resolves issue then you may need to schedule DNS cleanup.
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DionisisTAuthor Commented:
I've tried that and it will not help. If I powercicle the router for 2-3 minutes internet speed might return to normal and then back to oblivion...
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giltjrCommented:
If it is manageable you should be able to do.

What you would do is configure the switch to mirror the traffic for the port that the modem is on.

The connect a PC to that port and run Wireshark to capture the packets.
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DionisisTAuthor Commented:
@giltjr Ok done that and packets are comming. What am I looking for?

P.S. It's happening right now!
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giltjrCommented:
You want to look to see if any host is generating a TON of traffic.  That is enough traffic to eat up all of your Internet bandwidth.

Once you find that out, then you need to find what that host is doing.
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DionisisTAuthor Commented:
Ok i've captured 1012 packets. Of which 236 are UDP connections to external IP's from the server. 114 are from a user and many more are outgoing connections from the server to external IP's.

Do give you an example the following are incoming connections(many of them):
48      7.817920000      85.72.92.200      192.168.0.100      UDP      112      Source port: 60858  Destination port: odeumservlink
1012      94.929498000      79.129.16.89      192.168.0.100      UDP      176      Source port: 50546  Destination port: odeumservlink

And the following are outgoing connections:
931      88.319408000      192.168.0.100      79.129.16.89      UDP      112      Source port: odeumservlink  Destination port: 57985
943      89.163910000      192.168.0.100      85.72.92.200      UDP      112      Source port: odeumservlink  Destination port: 60858

Also one thing that i forgot to mention is that on the server is running Hamachi. Someting that i have to use...
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giltjrCommented:
If the UDP traffic "disappears" from the packet capture then that is most likely your problem.

I believe that  Hamachi I believe it uses UDP to setup VPN connections.  So what do you use VPN for?

Could your server be VPN'ing outbound to distribute "information" or to do a backup every 10 days?

If possible I would check to see if that server has a task that is scheduled to run every 10 days.
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DionisisTAuthor Commented:
Hamachi is used by our 2 abroad offices. We have a CRM Software and Hamachi emulates local network connection for these two offices. But from time to time i see errors in event viewer about printer drivers i dont have in my network.
I thing i have to blame Hamachi for this...
Right now i have dissabled Hamachi but network speed is still slow...
Any way... i have to go now. Thanks for your help. I'll get back to you on Monday.
Have a great weekend!!
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DionisisTAuthor Commented:
Internet speed is still good. Next time I experience slow internet speed I will do a ten minute packet capture. @giltjr thank you for your help and suggestions.
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