DHCP Relay Layer 3 - How to communicated with Bolt again without Reset

Anybus Support Anybus Wireless
#1

Hello, we are using the Anybus wireless bolt to connect our PLC to our DHCP network.

When you use a layer 3 dhcp relay the PLC will get and IP and connect to the network perfectly.

But from the network perspective it is the Bolt’s MAC id that is connected and the IP shows the IP that the PLC received.

The bolt no longer has an IP to to communicate with (via telnet, AT commands)

I’m wondering if there is anyway to communicate with the Bolt directly in this operating mode without using a serial port?

Any help would be greatly appreciated

#2

Hi Bradley,

It sounds like you are actually using “Cloned MAC” mode, shown here, where the Bolt acts as the PLC’s wireless network adapter, and no longer has it’s own IP address. You will no longer be able to communicate with the Bolt over the network.

If you would like to attach the PLC to network and still be able to communicate directly with the Bolt, use the “Wireless Bridge” mode shown here.

Kyle

#4

Hi Kyle thanks for the response. That diagram is exactly how its setup. Including the part where its using layer 3. DHCP relay would not work with layer 2.

When doing this I can’t access the Bolts IP. On the network I can see the Bolts MAC with an associated IP but that is the IP of the PLC. The network is dhcp so the bolt gets its dhcp and I suppose it only gets one lease and the IP assigned is used for the plc and the bolt is unattainable. I’m wondering if you can try to replicate this in you end?

Cheers,
Brad

#5

Actually what I’m trying to do is the next page (A5. Single ethernet to wlan).

It mentions that the web page may become unavailable. I’m wondering if there is anyway to ping
/ communicate with the bolt after this.

#6

No, with this mode the bolt is essentially a wireless network interface of the PLC. All traffic is forwarded to the PLC and the Bolt is transparent.

If you must retain access to the Bolt, I would recommend the setup in A4.

#7

Thanks Kyle, so I’ve tried that aswell.

If it were on a static network I would be able to see the bolt. But on DHCP the bolt does not have its own IP. Only the IP of the PLC is present (with the Mac of the bolt). This is layer 3 and a normal DHCP network with no funky security.

I cannot communicate directly to the bolt but we need to.

#8

Hello @Bradley_Lauder,

Kyle asked me to take a look at this issue with him.

A quick resolution here would be to be to block off and ip address on the DHCP server and then statically assign it to the bolt. This would ensure that the Bolt has an address in that subnet and is not relying on receiving one from the DHCP server.

We can run into several issues that are not easily resolved with the bolt and DHCP. Since DHCP works between layer 2/3 we tend to see odd issues. Using MAC clone mode you have 1 MAC address being used then expecting the DHCP server to assign 2 addresses. With layer 3 mode not all the messages for DHCP are sent thought he Bolt. We get around this with our DHCP forwarding, where the Bolt is forwarding DHCP requests down the the LAN. This ensures your LAN devices get addresses. As you have seen this causes some issues with the Bolt getting addresses.

Deryck

#10

Topic closed due to inactivity.