One Server -2 NICs, Different IPs
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Hi Guys,
I just picked up a new SMB customer. He has a 2012R2 server and apparently it's been configured to use both NICs with different IPs. I found this article here:
And it discusses a use case for this but I was troubled by this:
"It's important to note that applications other the file server and file client might not behave properly with this configuration (they might not listen on all interfaces, for instance). You might also run into issues updating routing tables, especially in the case of a failure of a NIC or removal of a cable. These issues are documented in KB article 175767. For these reasons, many will not recommend this specific setup with a single subnet."
My first thought is to go and disable the secondary NIC, but can you guys think of any use cases I'm unaware of that might discourage me from disabling? From what I can gather his server is handling DNS, but not DHCP (I'm planning to change that). It's also a file server/SQL server. I just don't see the necessity of having that secondary NIC other than possibly creating issues.
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That's called "dual homed."
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Well, there is probably a reason that this was done. We can't say why you should disabled the second NIC if we don't know why it is there.
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If you don't need 2 IP addresses, team those bad boys and increase throughput.
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Is it doing any routing? Like @scottalanmiller said, I wouldn't shut it off until you know exactly what it's doing.
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When I did the initial onsite visit I thought the secondary connection was some sort of iLO or iDrac connection (not sure if Lenovo has a version & what it's called), but I can now see it seems like it's performing redundancy which isn't a huge concern as there are only maybe 6 users of this server. Like SAM said I should probably do some more digging before I disable it.
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This 2012 Server is not also a DC is it?
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From my brief look at the server AD role is installed but I don't believe any of the computers are members of the domain
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@frodooftheshire said in One Server -2 NICs, Different IPs:
When I did the initial onsite visit I thought the secondary connection was some sort of iLO or iDrac connection, but I can now see it seems like it's performing redundancy which isn't a huge concern as there are only maybe 6 users of this server. Like SAM said I should probably do some more digging before I disable it.
That is a possibility. I've seen people create a different IP for each NIC and then as "redundancy" call one A and one B in DNS. No idea what they are thinking, but I've seen it done.
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@frodooftheshire said in One Server -2 NICs, Different IPs:
When I did the initial onsite visit I thought the secondary connection was some sort of iLO or iDrac connection (not sure if Lenovo has a version & what it's called), but I can now see it seems like it's performing redundancy which isn't a huge concern as there are only maybe 6 users of this server. Like SAM said I should probably do some more digging before I disable it.
Redundancy doesn't happen with a different IP address.
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@scottalanmiller said in One Server -2 NICs, Different IPs:
@frodooftheshire said in One Server -2 NICs, Different IPs:
When I did the initial onsite visit I thought the secondary connection was some sort of iLO or iDrac connection (not sure if Lenovo has a version & what it's called), but I can now see it seems like it's performing redundancy which isn't a huge concern as there are only maybe 6 users of this server. Like SAM said I should probably do some more digging before I disable it.
Redundancy doesn't happen with a different IP address.
Correct. That's why it's in quotes. They called it redundancy and used computerB instead of computerA to connect...
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@scottalanmiller Maybe I worded that wrong. I was just implying that because they had separate IPs they weren't utilizing the both nics in an effort to team them. In other words I had ruled out bandwidth aggregation, and figured they were trying to accomplish some sort of network redundancy.
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@frodooftheshire said in One Server -2 NICs, Different IPs:
@scottalanmiller Maybe I worded that wrong. I was just implying that because they had separate IPs they weren't utilizing the both nics in an effort to team them. In other words I had ruled out bandwidth aggregation, and figured they were trying to accomplish some sort of network redundancy.
Reverse that logic. Since we can rule out redundancy, does that imply that they were trying to get better throughput?
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lol, sounds like there was just a failure of understanding by the previous IT person.
I'm also wondering if it's virutalized, and if not, why not?
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You could check for an IIS instance and see if it is listening on all IPs, or just a specific one. Then check DNS and see if there are entries for the second IP.
If it's a small network I would disconnect the extra NIC and listen for the screams. If you're remote when the call comes in, just add the second IP to the first NIC and that should get things going again.
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Here's a thought - are the IPs on two different subnets?
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Sometimes, the only way to find out what something does is to unplug it, then wait by the phone.
Haha, just kidding... but not really. Be careful!
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@Dashrender The two IPs are on the same subnet. Yesterday when I was just gathering information remotely about different devices on the network via Advanced IP scanner that's when I saw same hostname/different IPs
When I tried to access 55.6 in a browser it loaded an IIS welcome page. That's the extent of what I know for now.
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@Tim_G I could always disable the port on the switch and if the screams come in switch it back on. Like most clients I take on the customer has zero documentation on how things are setup/configured. Maybe I'll be able to have a conversation with the old IT guy and see if he's willing to share on why things the way they are.
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Open up resmon.exe, network tab.
TCP Connections section, then look at Local Address for the IPs, and see what's connecting to them.
