Bad Pings from Windows, Good from Linux
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Weird networking issue. We have some Windows machines (mostly server VMs, but desktops too) and some Linux servers on a network with some print servers (old IOGear stuff.) The Linux machines can ping the print servers no problem, 100% success. Linux can ping Windows and vice versa. No network problems at all, until the Windows machines try to ping the print servers. Then there is 15-40% packet loss. We have no idea what could be wrong.
There are only two switches and we can't find any correlation there. Nothing is on wifi. Nothing crosses a router boundary.
Same physical adapter with Linux vs. Windows VMs the Linux can ping reliably and the Windows cannot!
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The windows desktops have the same issue as the VM's do?
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is there there a speed difference at which Linux pings vs Windows?
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Wireshark.
On the Windows side first and then on the print server using a mirror port.
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- Subnet masks set properly across the board?
- Multiple IP addresses set on the adapters on the windows hosts?
- Ping by hostname vs ping by ip?
- AV or security software that's only on the Windows machines?
A strange one for sure, but it's got that weird "of course that was the problem" vibe.... let us know what it ends up being, I'm curious now
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The speed of the vnics wouldn't be a factor in packets being dropped.
@scottalanmiller do the windows vms have updated drivers installed?
I believe you said that the linux and windows systems are using the same vnic device type, correct?
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@Dashrender said in Bad Pings from Windows, Good from Linux:
The windows desktops have the same issue as the VM's do?
Yeah
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@DustinB3403 said in Bad Pings from Windows, Good from Linux:
The speed of the vnics wouldn't be a factor in packets being dropped.
@scottalanmiller do the windows vms have updated drivers installed?
I believe you said that the linux and windows systems are using the same vnic device type, correct?
Totally up to date across the board, yeah. Same NIC and VNIC, yes.
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@notverypunny said in Bad Pings from Windows, Good from Linux:
Subnet masks set properly across the board?
Definitely (it's just /24 so easy to get right.)
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@notverypunny said in Bad Pings from Windows, Good from Linux:
Multiple IP addresses set on the adapters on the windows hosts?
Nope, looked for that on both sides.
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@notverypunny said in Bad Pings from Windows, Good from Linux:
Ping by hostname vs ping by ip?
Only testing IP. Don't believe any DNS entry even exists for the machines in question.
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@scottalanmiller Corrupt Arp Table (cache)?
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@Dashrender said in Bad Pings from Windows, Good from Linux:
is there there a speed difference at which Linux pings vs Windows?
https://feelingsec.wordpress.com/2018/01/04/fingerprinting-with-ping/
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@Dashrender said in Bad Pings from Windows, Good from Linux:
is there there a speed difference at which Linux pings vs Windows?
Not sure why @DustinB3403 downvoted this, but you are correct.
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@scottalanmiller said in Bad Pings from Windows, Good from Linux:
Weird networking issue. We have some Windows machines (mostly server VMs, but desktops too) and some Linux servers on a network with some print servers (old IOGear stuff.) The Linux machines can ping the print servers no problem, 100% success. Linux can ping Windows and vice versa. No network problems at all, until the Windows machines try to ping the print servers. Then there is 15-40% packet loss. We have no idea what could be wrong.
There are only two switches and we can't find any correlation there. Nothing is on wifi. Nothing crosses a router boundary.
Same physical adapter with Linux vs. Windows VMs the Linux can ping reliably and the Windows cannot!
Not many companies even use ping anymore. I'm sure you are testing this because of network performance issues not just solely based on ping.
What's the performance issue specifically?
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@JasGot said in Bad Pings from Windows, Good from Linux:
@scottalanmiller Corrupt Arp Table (cache)?
In the same vein as this: could there be duplicate MAC addresses in play? Cloned VMs? P2V? Restored / Replicated VMs.... Or someone just trying to get around MAC security somewhere?
I assume that physical cables and connections have been checked / swapped / ruled out?
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@IRJ said in Bad Pings from Windows, Good from Linux:
@scottalanmiller said in Bad Pings from Windows, Good from Linux:
Weird networking issue. We have some Windows machines (mostly server VMs, but desktops too) and some Linux servers on a network with some print servers (old IOGear stuff.) The Linux machines can ping the print servers no problem, 100% success. Linux can ping Windows and vice versa. No network problems at all, until the Windows machines try to ping the print servers. Then there is 15-40% packet loss. We have no idea what could be wrong.
There are only two switches and we can't find any correlation there. Nothing is on wifi. Nothing crosses a router boundary.
Same physical adapter with Linux vs. Windows VMs the Linux can ping reliably and the Windows cannot!
Not many companies even use ping anymore. I'm sure you are testing this because of network performance issues not just solely based on ping.
What's the performance issue specifically?
Who doesn't use ping? That's weird. Hard to get more basic than that for layer 2 testing.
Yes, the print servers routinely fail from Windows.
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@notverypunny said in Bad Pings from Windows, Good from Linux:
I assume that physical cables and connections have been checked / swapped / ruled out?
Same ones as the pings that work. So physically connections are ruled out.
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@notverypunny said in Bad Pings from Windows, Good from Linux:
Cloned VMs? P2V? Restored / Replicated VMs
I believe that this is the case, but the old ones are definitely powered down.
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@scottalanmiller said in Bad Pings from Windows, Good from Linux:
@notverypunny said in Bad Pings from Windows, Good from Linux:
I assume that physical cables and connections have been checked / swapped / ruled out?
Same ones as the pings that work. So physically connections are ruled out.
I’m curious. Is there a physical Cisco switch in play?
