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How to choose "rational" IP address for PXI?
Bob_Schor
Knight of NI
07-21-2008 01:04 PM
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I'm "rebuilding" some data acquisition systems and am trying to make "rational" choices wherever possible. Our "host" machines are PCs that are connected to a University network, and thus have assigned (or DHCP-provided) IP addresses. In all cases, we are communicating with a PXI box through a separate NIC in the PC that is wired directly (via crossover or switch) to the PXI, and thus does NOT utilize the existing network wiring. We therefore have more-or-less free rein in choosing the IP address of both the Host (PC) cards and of the Remote (PXI) systems.
Many of the "legacy" systems that I will be replacing have a strange addressing scheme whose explanation has been lost in the Lore of Techs Past. Most Host systems use an IP of 169.254.41.179, with a subnet mask of 255.255.255.0, and no Default Gateway. The PXI typically has an address of 169.254.99.254. I know that 169.254.x.x is used for "automatic IP addressing" (when there is no DHCP server to assign an address), but don't see the utility in this case, unless there's a way for (a) the PC to "automatically" assign itself an address, (b) the PXI (and its RT side) to "automatically" assign itself an IP, and (c) for the two of them to "discover" the other so that when you need to start a remote system, you "know" its IP.
It actually seems to make more sense to me to use non-routable addresses in the 10.x.x.x range, perhaps saying 10.0.0.10 through 10.0.0.99 are PCs, 10.0.0.100 through 10.0.0.199 are PXIs, and the mask is 255.255.255.0. But I have no "rational" reason for this scheme, either, except to say the numbers are simpler and easier to remember.
While I'm asking, I have some questions about the need to use specific IPs, as opposed to "names". For example, to start a VI running on the PXI, I need to Open Application Reference, which requires an IP in x.x.x.x notation or a DNS-type name (as opposed to the target's name that MAX gave it). Is there a way to "discover" the IPs that are on my "private" line and identify which of them is the PXI? [This last question is really important -- in my Development setup, I have three PCs connected to the same switch as the PXI -- each PC plays a different role in development, so one is for Legacy Software (meaning LabVIEW 7), one for New Stuff (meaning LabVIEW 8.5), etc.].
Are there situations when the PXI needs to know its Host's IP? If so, is there a "programmatic" way to find out?
Thanks for the input and feedback.
Bob Schor
Many of the "legacy" systems that I will be replacing have a strange addressing scheme whose explanation has been lost in the Lore of Techs Past. Most Host systems use an IP of 169.254.41.179, with a subnet mask of 255.255.255.0, and no Default Gateway. The PXI typically has an address of 169.254.99.254. I know that 169.254.x.x is used for "automatic IP addressing" (when there is no DHCP server to assign an address), but don't see the utility in this case, unless there's a way for (a) the PC to "automatically" assign itself an address, (b) the PXI (and its RT side) to "automatically" assign itself an IP, and (c) for the two of them to "discover" the other so that when you need to start a remote system, you "know" its IP.
It actually seems to make more sense to me to use non-routable addresses in the 10.x.x.x range, perhaps saying 10.0.0.10 through 10.0.0.99 are PCs, 10.0.0.100 through 10.0.0.199 are PXIs, and the mask is 255.255.255.0. But I have no "rational" reason for this scheme, either, except to say the numbers are simpler and easier to remember.
While I'm asking, I have some questions about the need to use specific IPs, as opposed to "names". For example, to start a VI running on the PXI, I need to Open Application Reference, which requires an IP in x.x.x.x notation or a DNS-type name (as opposed to the target's name that MAX gave it). Is there a way to "discover" the IPs that are on my "private" line and identify which of them is the PXI? [This last question is really important -- in my Development setup, I have three PCs connected to the same switch as the PXI -- each PC plays a different role in development, so one is for Legacy Software (meaning LabVIEW 7), one for New Stuff (meaning LabVIEW 8.5), etc.].
Are there situations when the PXI needs to know its Host's IP? If so, is there a "programmatic" way to find out?
Thanks for the input and feedback.
Bob Schor
MXI Master
Member
07-22-2008 10:15 PM - edited 07-22-2008 10:15 PM
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Bob,
There is not much to selecting an IP address. But here are some good guidelines to follow. If these computers ever might be used on the university network, you may be able to get IPs reserved by the IT department and just use them. I would also suggest placing all of them on the subnet.
As for your second question, the PXI chassis should always know its hosts is as long as it is using a host.
Message Edited by MXI Master on 07-22-2008 10:15 PM
There is not much to selecting an IP address. But here are some good guidelines to follow. If these computers ever might be used on the university network, you may be able to get IPs reserved by the IT department and just use them. I would also suggest placing all of them on the subnet.
As for your second question, the PXI chassis should always know its hosts is as long as it is using a host.
Message Edited by MXI Master on 07-22-2008 10:15 PM
-Marshall R
