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Is it valid to have two network adapters on the same PC have the same network portion in their IPv4 address? If not why is my DHCP server doing so and how should I setup my DHCP server to have it give each different adapter a different IPv4 network assignment?

I have a Windows 7 PC with a Wired Ethernet and a Wireless LAN connection. The two network adapters are getting their IP address from the same DHCP server. The server is handing out addresses that are on the same network: specifically the 192.168.100.0 given the subnet mask of 255.255.252.0.

C:>ipconfig ...

Wireless LAN adapter Wireless Network Connection:
...
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::41b:a667:523b:b4d7%12(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.102.237(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.252.0
...
Default Gateway . . . . . . . . . : 192.168.100.1
DHCP Server . . . . . . . . . . . : 192.168.100.203
DHCPv6 IAID . . . . . . . . . . . : 305965556
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-18-D5-1B-EA-B8-CA-3A-D7-2C-47

Ethernet adapter Local Area Connection:
...
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::3d34:d5ae:d3eb:197d%11(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.102.224(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.252.0
...
Default Gateway . . . . . . . . . : 192.168.100.1
DHCP Server . . . . . . . . . . . : 192.168.100.203
DHCPv6 IAID . . . . . . . . . . . : 246991418
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-18-D5-1B-EA-B8-CA-3A-D7-2C-47
  • 2
    What's problem here? Or, probably more accurately... what do you think the problem is here? – HopelessN00b Aug 22 '14 at 14:44
  • 1
    All this means is both adapters are connected to the same network. Your question is not clear. The current behavior is what I would expect if both adaptors are connected to the exact same network. – Ramhound Aug 22 '14 at 14:47
  • Are they connecting to the same router? – heavyd Aug 22 '14 at 14:47
  • @heavyd - The information provided by the author clearly indicates that is the case. – Ramhound Aug 22 '14 at 14:49
  • @Op, what is your goal? do you plan to run different services on each nic, or are you trying to get something else out of this? – Frank Thomas Aug 22 '14 at 15:03
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Yes it is valid to have two nics on the same network. In the case of Windows, it has an algorithm to determine which interface is "best" when deciding how to send packets out to the network. Most likely, your wired connection will get precedence.

DHCP servers work on a broadcast basis. At startup, the PC will issue a DHCP broadcast request asking for an IP. The DHCP server will give an IP address in its configured address range that matches the interface the IP address came in on. A DHCP relay can cause it to choose a different range, by passing its own address as part of the request, and sending it unicast. Then the DHCP server will choose an address from the range matching the relay address.

In order to give your two nics different address ranges with DHCP, they will need to be on different networks separated at layer two - so separate VLANs or physically separate. Your DHCP server will either need to have a presence in both networks, or another device in between can act as a DHCP relay.

-1

More than one IP address in the same subnet on the same host (whether bound to the same adapter or to different adapters) are not only valid, but are routine in many applications (e.g. web servers).

It is, though, quite unusual to configure more than one with DHCP - unusual being the key word, not invalid.

  • What do you mean unusual to configure more than one with DHCP? DHCP is typically used to configure multiple network interfaces, or 1. You often specify a range with DHCP – barlop Aug 22 '14 at 14:48
  • It is unusual to configure more than one interface on the same host with DHCP, which is exactly what my answer says ... – Eugen Rieck Aug 22 '14 at 15:30
  • Why would that be unusual. Suppose you have a network of a few computers and are using DHCP anyway you put two adaptors in a computer and they're set to DHCP. Why is that unusual? Or you have just one computer and add an adaptor.. Why would DHCP be unusual there? – barlop Aug 22 '14 at 15:33
  • The definition of "usual" is how often such an approach is taken in relation to the number of such situations. This is, why it is unusual. – Eugen Rieck Aug 22 '14 at 15:37
  • well -usually- when something is usual, there is a reason why e.g. it's a default setting thus it's common, or some other reason. And even when things are just convention causing a norm, there's a reason. So there are reasons why particular things are usual, and that's what i'm trying to ask you. – barlop Aug 22 '14 at 15:46

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