Finding the IP address of my Opto B3000

I have an Opto 22 that was connected to a PC running Wonderware that crashed. I created a virtual machine and loaded all the software for Wonderware and the Opt 22 IO Manager. I am getting a communication error with the Opto 22 on the ethernet. I am by no means an expert on this hardware. I was trying to figure out what the IP address was for the ethernet connection and really do not know where to begin. I downloaded the manuals and tried to figure it out.

Since this was probably originally loaded with all defaults and nothing that would point to the exisiting network, can I assume that the connection is using loopback? If it is set to something else, how do I find out what the IP address would be? If I need additional equipment, please let me know (like the RS232 connector that I know for sure I don’t have).


Hi David,

Welcome to the forums! Sorry to hear your PC crashed. Don’t forget, our Product Support is FREE! and they’d be happy to help.

However, if you have PAC Manager – free to download, click here (older versions might’ve been called “IO Manager”), then you can use the “Find” tool to have it find Opto 22 Ethernet (MMP Devices) are on your network.

In PAC Manager, click Tools > Find Opto 22 MMP Devices, then click the “Find” button. The devices that respond will show their IP Address and other info. For example, in this list you see a SNAP-B3000-ENET there second from the bottom. I’m guessing that’s the type of hardware you have?

Hope that helps!

I would like to make a suggestion re-garding the FIND tool you mention here that has been bugging me for some time. The developers need to rethink the tool because although it works fine, your PC that you are running the tool on has to have the same subnet or it will not find the Opto devices. Since it should be using ARP to find the Opto22 devices, it should be able to find any mac address starting with 00-AD regardless of what subnet your PC is set to as long as the Opto22 device is not located across a routed connection. So for instance, if the Opto device is connected to a switch even if that switch is connected to another swtich etc, or in other words, if the network is a “FLAT” network meaning there are no routed connections between the opto device and the PC you are running the tool from, it should be able to find it. If you are on a different subnet, you will not be able to connect to the Opto device, however, all least you can set your PC subnet to the same subnet once you know what it is, then use the “IP Change” tool to change the Opto device and then return your PC back to the original subnet. This is a far better option than resetting the controller to factory defaults since you may have an untold number of persistent values that would get cleared.

Hi Barrett,

I’ll ask the PAC Manager developer(s) about how the find works, exactly. But in the meantime, could you clarify situation you’re addressing here? I know I’ve seen some strange things if my subnet wasn’t set correctly. Are you saying you’d like PAC Manager to find ANY Opto device, regardless of IP/Subnet? (Not sure if that’s possible, but there may be other ways to address the particular situation you’re pondering.)


Hi Barrett,

PAC Manager’s Find tool actually does a UDP broadcast of an MMP packet (the one to read the status read area which includes the firmware version and unit type, also displayed in the “Find” list). However, and this is getting a little more “advanced” than most people care to go, there is a trick you can do to leverage the ARP packets you mentioned.

When our Ethernet devices first establish a connection (like when you power one up), they send out a Gratuitous ARP you can sniff using a tool like Wireshark (the favorite of PSG). Since you know the MAC of the device whose IP address you seek, you can filter all the other network traffic with something like this:

Then turn on your mystery IP device and ta-da its packet shows up including that IP address. Here’s a little screen shot:

Hope that helps!

Ok, that’s a good tip, I’ll give it a try.
Ok, now I see why it works the way it does, obviously an UDP broadcast is of course IP so therefore, unless you are on the same subnet, it will not get a reply.
I am not an expert on ARP but since ARP is the means by which any device can talk to any other device (level 1) on a flat network (meaning that there are no routes between them). Regardless of the subnet your are on when you plug into a switch (or the switch on a router) the switch knows you exists and what your MAC address is, that’s how level 1 works. Even if that swtich is “bridged” or connected via a swtich to switch connection, the physical network is “flat” meaning that level 1 comms (ARP) can talk to any other device so connected to that physical network regardless of subnet.
Now I don’t know exactly how they do it, but Mikrotik routers all have a feature that is soooo usefull. Using a utility called Winbox, you can click on a button (…) that sends a command out (I assume an ARP command) that returns every device info including IP address and MAC address that is on a flat network regardless of how many bridged or switched connections that exist. If you pick on the MAC address of any device in that list, then you connect to that device via MAC address and therefore you can make any configuration changes you need to make on that device such as changing the subnet and IP to the subnet you are on. Have the developers chew on that one awhile…

Ok, I have a couple of things misrepresented in the post above. Of course ARP refers to address resolution protocol and that really refers to the relationship of IP addresses to MAC addresses. Therefore my use of ARP above is not correct. Also, I need to correct myself on the use of level 1. IP is level 3 and MAC (media access control) is level 2 and of course the physical medium is level 1.
I am refering to level 2 and the MAC protocols. Now just like in IP in MAC you have a broadcast address as well such as FF:FF:FF:FF:FF:FF. If this address is sent out, all devices will recieve the transmission.
Here is a quote from wikipedia:
"Ethernet frames with a value of 1 in the least-significant bit of the first octet[note 2] of the [URL=“”]destination address are treated as multicast frames and are flooded to all points on the network. While frames with ones in all bits of the destination address (FF:FF:FF:FF:FF:FF) are sometimes referred to as [URL=“”]broadcasts, Ethernet network equipment generally does not distinguish between multicast and broadcast frames."
So I don’t know how Mikrotik is implementing it, however, I suspect they are including some code in the stack of each device that will respond to a multicast address.

Yes, that’s what I am suggesting. Of course it isn’t possible if there is a route between you and the devices you are trying to seek, however, as long as there is not a route between these devices, regardless of what subnet they are assigned to you can find, communicate and even configure the device via mac address addressing. As I previously mentioned, MikroTik equipment is set up like this, as long as I am on a flat network (no routes) if the device I am trying to find addressed to a different network, I can click a little button instead of using an IP address that does a MAC broadcast for MACs that start with MikroTik’s prefix and it will pull up a list of IP and Mac of every MikroTik device regardless of subnet and IP address. I can then click on the MAC address of any of these nodes and open up Winbox and do full configuration tasks. The reason I am pushing this feature is that when you have a whole bunch of customers, vendors, partners that really are not network engineers, this is a big deal. If you don’t know what the address is of a device, then it’s a no brainer. Otherwise, you will likely have to reset the device to defaults to use it, and if there is a strategy archived on that device that is the only copy, then you have a real problem. Also, instead of having to change your PC’s IP subnet to the same subnet of a brain or controller, open it up, change the IP back to the subnet you came from, then reset your PC’s IP, you can do it all in one session by being able to set the IP address of this node from a different subnet and reboot it.