Network Related Issue - Sites Initially Slow to Load

There are several workstations, not all, on the same subnet that are experiencing the same issue. We also have some servers on another subnet also experiencing this issue. Again, not all servers on this subnet. For the sake of security, I’ve changed the subnets here.

•      10.0.1.0 – Offsite
•      10.0.2.0 – Onsite Workstations
•      10.0.3.0 – Onsite Servers

Workstations on subnet 10.0.2.0, are initially slow to load certain websites. I’ve run PING tests from several workstations and found that it takes approximately 30-45 seconds before I finally see successful PINGs. I used the “-t” and “-4” parameters during these tests. One site I noticed the issue on is Google.com. Once I get a successful connection, the site is fine. After about 5 minutes, the issue surfaces once again. I see this same issue with servers on subnet 10.0.3.0 to the offsite subnet 10.0.1.0. If I take the same workstation experiencing this issue and place it on the 10.0.3.0 subnet, the issue disappears.

This is especially critical, because backup jobs run onsite to offsite. Some jobs fail because of this issue. I have to login to the backup server on 10.0.3.0 and run a PING test with the parameters “-t -4” to the repository on 10.0.1.0. Once running continuously with successful PINGs, I can then run the backup job and it will run successfully.
mario00Asked:
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mbkitmgrCommented:
Download a copy of Axence Net Tools and get some data
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Fred MarshallPrincipalCommented:
It rather sounds like a DNS issue.  Once it's resolved and cached then it works.  Before it's resolved and cached, it's very slow.

I would run DNS Workbench: https://www.grc.com/dns/benchmark.htm
It's easy and you get some insight into DNS performance.

Are there DNS address differences between the slow computers and the normal computers?
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David FavorLinux/LXD/WordPress/Hosting SavantCommented:
What OS are you running, so people know what type of debug tools you can use.
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TjnoNetwork AdministratorCommented:
Did you check the devices, such as Switch cor Router? Are they okay?
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mario00Author Commented:
We are running Windows 7, 10, 2008, 2012. I will check out those tools and report my findings.
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mario00Author Commented:
Specifically, I have two workstations that I am working on (10.0.2.14 and 10.0.2.18). 10.0.2.14 is a Windows 10 64-bit. 10.0.2.18 is a Windows 7 64-bit. 10.0.2.18 does not experience this issue, while 10.0.2.14 does. I swapped the cables on the switch for the two workstations, and the issue does not follow. 10.0.2.14 still has the same issue. Now, while on the 10.0.3.0 subnet, the issue disappears. This tells me it cannot be a DNS issue, nor a switch issue. Furthermore, we do have other Windows 7 64-bit workstations that do have this issue. So, it is not related to the OS.
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Fred MarshallPrincipalCommented:
You tell us that there is a computer with IP address 10.0.2.14 that has the problem.
Then you say:
while on the 10.0.3.0 subnet, the issue disappears
But exactly HOW did this computer "get on the 10.0.3.0 subnet".  I am focused on DNS here and interested in knowing the DNS addresses that are in use.  So knowing the NIC settings in both subnet cases could be revealing.
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mario00Author Commented:
To answer your question, the jack feeding the workstation was moved from the 10.0.2.0 subnet to the 10.0.3.0 subnet on the switches. The 10.0.3.0 is a different switch than the 10.0.2.0 subnet.

A new development - I statically assigned a new IP address for four workstations experiencing this issue to different addresses on the 10.0.2.0 subnet (e.g., 10.0.2.14 became 10.0.2.114). The issue disappeared. Then, I statically assigned 10.0.2.14 to a workstation on the same subnet NOT experiencing the issue, and the issue followed.
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mario00Author Commented:
All workstations are using the same DNS servers, and there are no duplicate entries for different workstations.
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Fred MarshallPrincipalCommented:
I remain confused about this because I can't tell which addresses are being used overall.
I don't see how moving a cable to a different subnet than that which matches the NIC settings can work at all.  
There may be some routing ... ?
It appears that 10.0.2.14 has a problem but I don't know how it's connected and still don't know its DNS address - only that they are "all the same" which isn't much help for *me*.
It would really help if the information for the errant computers were more complete:
- which physical subnet is it connected to and what is the subnet network address?
- what are the ipv4 settings for IP, subnet mask, gateway, DNS servers?
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mario00Author Commented:
This image shows the actual IPs and subnets, DNS servers, and DHCP server. Also, to the right of the IPCONFIG output is the associated PING test.
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mario00Author Commented:
We created a new scope in our DHCP server that excludes the problematic IPs. Forced each workstation to grab a new one.
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mario00Author Commented:
Hearing of possible DNS issue led us to look into the DHCP server as well, which is where we found and fixed the problem.
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Fred MarshallPrincipalCommented:
Good to hear it's fixed!
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