Network card - weird problem

Issues related to configuring your network
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centare
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Network card - weird problem

Post by centare » 2021/02/02 12:02:10

I have a Supermicro server with inbuilt 1 Gbps network cards - I have later added a plugin 10 Gbps SPF+ cards with two ports.

I have not had an issue with it for a year on 10 Gbps card, suddenly it was offline for some reason and could not get it online. ifup etc. brings no errors, no firewall on the server itself. I managed to get it up on the inbuilt 1 Gbps card and it worked for a month. Now I can't get the network on the 10 Gbps card up and several times a month, the server just goes offline on the 1 Gbps network card and I can't ping my gateway or anything. It requires reboots, activate and deactivate the network card and then it works again for a while.

Note that I have 4 cables in total, to different switch ports (enterprise switches). I have only tried to configure one card at a time.

When I run route-command during the offline time, it takes maybe 10 seconds. When it is online like now, it takes less than a second.

I have over 100 servers in this network at the data center and I have done this for 10 years. But I'm clueless - what could this issue be? Routing table looks correct even when down. But I can't even ping the gateway, it is like a fw (but not fw activate, I have checked). Many reboots and activate/deactivate network card fixes it for the 1 Gbps inbuilt network interface. I'm using nmtui.

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TrevorH
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Re: Network card - weird problem

Post by TrevorH » 2021/02/02 14:24:28

The easy bit to answer is
When I run route-command during the offline time, it takes maybe 10 seconds. When it is online like now, it takes less than a second.
Either don't use the route command (which has been deprecated for more than a decade) and switch to ip route show or remember to include the -n switch the route command so it doesn't attempt to do DNS reverse lookups on all your ip addresses through a network card that isn't working.

For everything else you'll need to look in your logs, specifically /var/log/messages, and find out why it stops.
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centare
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Re: Network card - weird problem

Post by centare » 2021/02/03 16:45:33

I now had both .34 (1 Gbps card) and a .35 (10 Gbps) IP running. I could ping both IP.

I deactivated .34 card (ifdown eno2 command). Then not only first card stopped working, but both.
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iproute.png
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network.png
network.png (228.69 KiB) Viewed 181 times
Last edited by centare on 2021/02/03 17:01:18, edited 1 time in total.

centare
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Re: Network card - weird problem

Post by centare » 2021/02/03 16:50:54

In my dmesg log, I get one weird entry (even though it says it is up) that possible SYN-flood (see attachment).
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network-manager.png
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dmsg.png
dmsg.png (203.3 KiB) Viewed 177 times

centare
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Re: Network card - weird problem

Post by centare » 2021/02/03 17:08:45

I can't see any errors in route, in ip addr show or in /var/log/messages (at least none that makes sense to me). It shows connected, it shows correct addresss (I have even changed IP to the IP of the 1Gbps card just to make sure). I can't ping my gw or find anything usefull when running on the 10 Gbps card (that I ran on before).

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TrevorH
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Re: Network card - weird problem

Post by TrevorH » 2021/02/03 17:36:52

For network related problems, if you obscure the ip address info, it makes it impossible for anyone to help you. We either need complete information or you will end up having to fix this on your own.

I'd suggest posting the various /etc/sysconfig/network-scripts/ifcfg-* files for the interfaces in question.
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centare
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Re: Network card - weird problem

Post by centare » 2021/02/03 20:26:40

These are public IPs, not local, so you might see why I don't want to post it here. They are all in same IP-range.

I can't see anything unusual in those files and I have used Centos for 10+ years. Just one day, it stopped working without doing any changes at the time.

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jlehtone
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Re: Network card - weird problem

Post by jlehtone » 2021/02/07 15:32:31

centare wrote:
2021/02/03 20:26:40
They are all in same IP-range.
Note: More than one IP on same broadcast domain is usually trouble.

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