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I have a Linux server running CentOS 5.6 (64-bit) that was running fine using the onboard NIC. For testing an HP PCI-e NIC was installed too but the server wouldn't respond on the network through eth0 or eth1 and the server then threw a debug message that it was disabling INT 50 so I presumed there was some conflict between the two NICs.

Unfortunately, the server will now not communicate through either the onboard NIC (HP card removed) or the HP card with the onboard NIC disabled - in both cases the server confirms it has an eth0 card and ifconfig returns sensible values, but the server's not PINGable and you can't PING anything on the network. If the NIC is set to use DHCP it won't get an address. The patch lead has been tested and also replaced.

I get the feeling that this is still an interrupt-related issue (lspci shows the NIC on INT 50), so when Linux/CentOS disables an interrupt is this written down in a config file somewhere that now needs to be manually edited?

Any thoughts appreciated before I try resetting the BIOS config back to factory defaults and/or begin to suspect that something's been damaged.

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A quick and dirty test against "suspected damage" is to utilize a bootable distro like Ubuntu to verify functionality (assuming the hardware utilized is fairly standard and covered by the drivers included within the distro). – user48838 Jul 2 '11 at 8:01
@user48838: Yep, that's on the list for tomorrow (Monday) if there's nothing obvious to check with the running installation - thanks. – Linker3000 Jul 3 '11 at 16:04

Have you installed the official HP driver module for this NIC? Some HP cards (notably some from NetXen) are not correctly supported by the RHEL5 kernel and will act in various broken ways unless the correct driver is used.

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Thanks but the card isn't in the server any more. – Linker3000 Jul 3 '11 at 16:03
up vote 0 down vote accepted

Well, a BIOS reset to factory defaults and then a quick tweak of things like disk boot order, disabling onboard sound and it's working again.

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