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Pallanon

Router Communication Issues

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Good Morning everyone, It has been a long time and I was wondering if someone could lend me some advice. We installed a new piece, rebuilt actually, of machinary that is running a HMI, Local Flexbus with 1794-L34, 1788-ENBT net card all tied in with a router. When I first tried plugging into the router, Windows (XP Profressional) did not see anything their. I do believe it has the service pack II installed. Well anyhow, I could not see anything on the network and need some advice in setting this up. RSLinx driver- ethernet devices- what would be a default address I could use to get into the network? Getting spoiled with cpu's already networked in and can not for the life of me remember if the service pack II is the issue or maybe even this windows live onecare is causing me all the problems thankyou... Pall

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Do you know the IP addresses of the Ethernet devices?

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Use the Ethernet/IP driver, instead of the ethernet devices driver. When you configure the driver, just tell it to browse the local subnet. You will need to know the first 3 octets of the controller's I.P. address and its subnet mask to configure your PC network card. Also, you may have to disable the XP firewall, or modify a rule allowing RSLinx to connect with the Ethernet/IP driver. Is this a new CPU/program? If not, you should be able to get the IP address/subnet mask form the offline program.

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When you deal with Ethernet modules that don't display their addresses (like the 1788-ENBT, 1769 daughtercard and 1756-ENET) the best and easiest thing to do is bridge to them from the controller's serial port and use the RSLinx module configuration tool to figure out (and maybe change) their IP address. Modules that lack backplane access are a harder challenge; usually I have to use the BOOTP utility to force them to start communicating, or use some sort of ARP mechanism to sort out their IP address if I know their MAC IDs. When troubleshooting RSLinx Ethernet comms, start by making sure that you can PING and make HTTP requests to the controller interface modules. Once you have those mechanisms working, you can start worrying about firewalls and RSLinx drivers.

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The BootP I know about and have used with great success. What is this ARP mechanism you refer to. Does it come with the RSLogix Software.

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Address Resolution Protocol (ARP) is a part of the TCP/IP protocol suite that is largely under-the-hood. Your computer has a cache of hardware MAC ID's and the IP addresses that those hardware devices use. You can see it by bringing up a command prompt and typing "ARP -A". One handy way to "fill up" the ARP cache is to execute a "Broadcast PING", in which you ping an address with the last octet set for 255. My computer's ARP cache after pinging 10.84.92.255 shows as : Internet Address Physical Address Type 10.84.92.1 00-0b-fd-cf-13-3b dynamic 10.84.92.29 00-04-00-07-87-75 dynamic 10.84.92.79 00-00-bc-1d-3d-ff dynamic 10.84.92.101 00-00-bc-22-a1-9c dynamic I happen to know that the MAC ID's that begin with 00-00-bc are all Allen-Bradley Company built Ethernet devices. I've used this technique on computers that were already connected to my customer's networks but they had lost their RSLinx configurations and had somehow forgotten the IP addresses. There are some other things you can do with ARP and reverse-ARP, especially if you're running a UNIX OS. I'd like to learn more about these to help me with the occasional instance where I have a device whose MAC ID I know but has never been hooked up and won't respond to the BOOTP Force command.

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Thanks for the great tip. I was unaware you could do that

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Just goes to prove there will always be more to computers than point and click. Thanks Ken - Rep Points to you for a great hint.

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When you say you broadcast ping, what actually do you mean. Is it just pinging an ip address with the last 3 digits being 255. Sorry about this everyone, just trying to get into the ethernet communication side of it better... Hopefully I can give it a try tonight Thanks again for your help Pall

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If you send a PING command with the last octet as "255", all the devices on the IP subnet should respond to the PING, which fills up your ARP cache with the addresses of everything on the subnet. "ping 192.168.1.255" will be responded to by every device with the subnet number "192.168.1" and the subnet mask "255.255.255.0". This is a neat trick, but is not the best way to solve your FlexLogix and router and Windows configuration issues. Connect up to the FlexLogix with a serial cable, browse through to the 1788-ENBT, right-click and select Module Configuration to see the -ENBT's IP address. If it's not correct, change it ! Then return to your PC and try to access the 1788-ENBT with a mechanism other than RSLinx. Use PING from a command prompt, or enter the IP address into a Web browser. If both of those techniques work, you can move on to troubleshooting the interaction between RSLinx and the Windows firewall and the router. If they don't you can concentrate on the non-RSLinx parts of your communication system.

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