CentOS 8 Network Connectivity Issue (Hosted on Hyper-V)

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jamesmcbride
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Joined: 2021/02/03 10:06:46

CentOS 8 Network Connectivity Issue (Hosted on Hyper-V)

Post by jamesmcbride » 2021/02/03 10:09:42

I have an issue with CentOS 8 running HAProxy, running on Hyper-V. I'm pulling my hair out with this one, any advice / ideas would be great.

I have a hyper-v 2012 R2 cluster running multiple VM's with good redundant networking throughout. There are other HAProxy VM's on this cluster which have no issues, these are our first pair of CentOS 8 HAProxies.

The deployment is fairly typical with two identical VM's running HAProxy and keepalived. The issue occurs on either VM in the pair.

Topology is:

Internet --> Firewall (checkpoint) -Network1-> These CentOS 8 VM's -LB Network-> Backend Servers

The backend servers are running Exchange 2016 on Windows Server 2016

Symptom - after a period of time (around 2-3 weeks) the VM will start getting intermittent network connectivity to the hosts it is load balancing

I have one of these CentOS 8 vm's exhibiting the issue at the moment. It seems if I fail this over (live migrate) to another node then the issue goes away.

I have left a constant ping running from the CentOS 8 VM to one of the backend servers and see no dropped pings.

If I manually try to curl one of the exchange servers around one in eight requests just times out.

I've tried running a tcpdump while the issue is happening, with a filter that I believe should show syn requests:

Code: Select all

tcpdump -i eth1 -nnSX "tcp[tcpflags] & (tcp-syn) != 0 && port 80"
When the issue occurs I don't see anything captured by tcpdump, which to me suggests that the request isn't even reaching the network adapter, suggesting it's either a driver or os issue? Or maybe a connection table that's full?

I'm seeing nothing untoward in /var/log/messages

Any pointers would be greatly appreciated before I resort to rebuilding with CentOS 7

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jlehtone
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Location: Finland

Re: CentOS 8 Network Connectivity Issue (Hosted on Hyper-V)

Post by jlehtone » 2021/02/03 12:19:25

jamesmcbride wrote:
2021/02/03 10:09:42
Any pointers would be greatly appreciated before I resort to rebuilding with CentOS 7
I can't help with Hyper-V or HAProxy but have to point out that due to "shift of focus"
CentOS Linux 8 will end at the end of this year: viewtopic.php?f=9&t=76599
CentOS Linux 7 should still last to 2024.
There are/will hopefully be some alternatives for CentOS Linux 8.

Does that change the "fix vs rebuild" cost analysis?

jamesmcbride
Posts: 2
Joined: 2021/02/03 10:06:46

Re: CentOS 8 Network Connectivity Issue (Hosted on Hyper-V)

Post by jamesmcbride » 2021/02/03 14:53:45

jlehtone wrote:
2021/02/03 12:19:25
jamesmcbride wrote:
2021/02/03 10:09:42
Any pointers would be greatly appreciated before I resort to rebuilding with CentOS 7
I can't help with Hyper-V or HAProxy but have to point out that due to "shift of focus"
CentOS Linux 8 will end at the end of this year: viewtopic.php?f=9&t=76599
CentOS Linux 7 should still last to 2024.
There are/will hopefully be some alternatives for CentOS Linux 8.

Does that change the "fix vs rebuild" cost analysis?
Certainly does, thank you! Did not realise CentOS 8 is out! Many thanks

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