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VMware server and multiple NICs in VLANs

Posted on 2008-02-04
Medium Priority
Last Modified: 2012-06-27
Hi experts,

This question is about VMware server, but also configuration of the physical network adapters of the Host.

What we have is a dedicated server hosting VMware server. The server has two NICs.

Recently we put each NIC in a sepperated VLAN: NIC1 in 192.168.171.x and NIC2 in 192.168.172.x
Both NICs get a static IP since it's a server.

Now, if i want to configure a gateway on both interfaces, windows (2003) complains:
"Warning - Multiple default gateways are intended to provide redudancy to a single network (such as  intranet or inet). They will not function properly when the gateways are on two separate, disjoint networks."

Question is, can i do this or not? All VMs should be mapped to NIC2 and the host machine should be on NIC1 for easy internal management. If i configure two gateways (one on each NIC) will the VMs and host do the correct routing?

Border Router -> VLAN1 -> 192.168.171.x -> NIC1 (host machine)
              -> VLAN2 -> 192.168.172.x -> NIC2 (VMs)

Question by:techneitsolutions
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LVL 12

Expert Comment

by:Amit Bhatnagar
ID: 20813176
If you provide DGs on both the NICs, you will definitely have Routing issues. This is by design and that is why providing multiple DGs on a single machine is not recommended. Since, Host machine will only be using NIC 1 for Connectivity and VMs will use NIC2, I see no reasons why you should provide a DG on NIC 2. Even if VMs will bind to NIC 2, they will only use the instance of NIC 2 and not the actual NIC2. By that, I mean that even if 4 machines will use NIC 2, you will be providing TCP\IP properties within the OS runnung under VMs and not the actual Host NIC 2 so If you ask me, providing only the basic TCP\IP properties on NIC should be enough.


Please read this for more information. Do let me know incase you need more clarification. :)
LVL 12

Expert Comment

by:Amit Bhatnagar
ID: 20813195
Also, why not use single NIC for both VM and Host Machine? Unless ofcourse, you are planning to put VMs on a separate NIC intentionally. Both these NICs are on the same machine so you will not be able to isolate VMs or keep them separate from Host anyways.

Author Comment

ID: 20813362
Bamit99 what you say is true in your 2nd post. But each NIC is connected to a different VLAN, not only the ranges of the networks differ.

It's so that servers and client pc's are in different vlans. but the VMs should also be on the IP range of the clients.

So what i need to know is, do i have to set GW's on both nics or is one just fine and if so will the VMs be able to do routing? So, what i understand from the first reply is to only set GW and DNS lets say on NIC1 on the 171.x range.

Current settings are:

NIC1 (used for host):

NIC2 (VMs should be bridged to this NIC):
GW: -
DNS: -

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LVL 12

Accepted Solution

Amit Bhatnagar earned 2000 total points
ID: 20813381
Exactly, if the second NIC is not helping the Host machine connect to any resource, then why to put any information on it like DNS, DG etc besides IP. And all the settings are going to be within VMs anyways. No need to put the settings on the second NIC. Only the IP should do..

Author Closing Comment

ID: 31427740
Right, thx for the fast support :)

I'll accept the answer since i'm sure this will work.
LVL 12

Expert Comment

by:Amit Bhatnagar
ID: 20813405
You are welcome...And do let me know incase this does not, we can always discuss more...:) Cheers !!

Expert Comment

ID: 24914882
Mapping Virtual Machines to single NIC on a host can cause NETBIOS Problems and Window CIFS Issues when copying files between the host and the VM's.  Broadcasting and MAC Addresses get a little funky

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