Connecting dual NIC server directly to two switches

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MikeOrlando02

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Jan 25, 2014
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I have a gigabit network where my server is connected to switch A and then switch A is connected to switch B. Users on switch B experience slow network connections (long network logins). These are low-end, unmanaged switches so I cannot take advantage of port bonding.

Can I use the second NIC in my server to connect the server directly to switch B (leaving the first NIC connected directly to switch A).

I believe that DNS would show the same computer name with two IP addresses and would determine which IP address to use by round-robin. My question is would a client on switch B see the new connection between server and switch B as having a lower metric and hence always use this IP/connection or would it continue to do round-robin regardless?

Clearly the best solution would be to replace both switches with those that could take advantage of port bonding and then use port bonding on the dual NICs to increase both the connections between the switches AND the connection between switch A and server, but it's not in the budget!
 
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You cannot put both nics on the same subnet and if you were to bridge the nics and use a virtual nic you would create a loop which the unmanged switches may or may not block depending on if they support basic spanning tree.

The only way to do this is to put the second nic in a completely different subnet and then assign the PC either a IP in that subnet or a secondary IP in the subnet and the rig the DNS to give the pc on switch 2 the ip of the nic2 for the server.

Still this is likely not your problem.

If you had a capacity issue with the gig port going to the server all users on both switches would have a problem not just the users on switch b. Because the users on switch a can access the server it means you likely have no...
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bill001g

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Aug 9, 2012
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You cannot put both nics on the same subnet and if you were to bridge the nics and use a virtual nic you would create a loop which the unmanged switches may or may not block depending on if they support basic spanning tree.

The only way to do this is to put the second nic in a completely different subnet and then assign the PC either a IP in that subnet or a secondary IP in the subnet and the rig the DNS to give the pc on switch 2 the ip of the nic2 for the server.

Still this is likely not your problem.

If you had a capacity issue with the gig port going to the server all users on both switches would have a problem not just the users on switch b. Because the users on switch a can access the server it means you likely have no issues with the port going to the server.

The only common link that users on switch b share that users on switch a do not is the connection between the switches. Since it is suppose to be a gig port it should cause no bottleneck since in theory the connection to the server would hit the 1g capacity before the connection between the switches.

Unfortunately there is no way to tell the utilization of the connection between the switches on a unmanged switch. The only way it could actually be using 1g would be if there was traffic between end users devices on switch a and switch b that in addition to the traffic to the server it exceeds the port capacity. I would load a tool like iperf and use the UDP option and see how much traffic you can push between clients on the 2 switches.

My best guess is that the switches somehow negotiated something strange like 100m or worse 100m half duplex.
 
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MikeOrlando02

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Jan 25, 2014
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Thank you for your reply. I believe that I am understanding you correctly.

I also see what you are saying about it being more likely that I would exceed the capacity of the NIC on the server before I exceed the gig connection between the switches.

Even with after hours use, it seems that users on switch B suffer significantly longer login times that those on switch A, I have always attributed that to the connection between the switches.

I believe this switches are connected using a straight connection and we were relying on the switch to auto everything. I would not be surprised if they were running at 100. I will take another look when I am on site. Maybe try a cross over, but this should be accounted for automatically.

Thanks
 
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