control logix 32e

[drusso 0]

we are using ethernet for the hmi to plc comms. the plc is a controllogix L32E. we are running version 19.1 firmware at the plc. the plc is set for 100 mbs. full duplex mode. when we ping the plc the ping shows TTL at 64. when we ping our Eaton HMI on the same network the ping shows TTL at 128. seems the plc is not running at full duplex. can somebody help or explain why the ping results are not the same? also how we can achieve the same ping results at the plc? thanks, dave

[Joe E. 259]

You may find THIS LINK useful.

[Shiner 2]

Right, Time To Live is not the ping return speed measured in milliseconds. C:\>ping 192.168.1.103 Pinging 192.168.1.103 with 32 bytes of data: Reply from 192.168.1.103: bytes=32 time<1ms TTL=255 Reply from 192.168.1.103: bytes=32 time<1ms TTL=255 Reply from 192.168.1.103: bytes=32 time<1ms TTL=255 Reply from 192.168.1.103: bytes=32 time<1ms TTL=255 Ping statistics for 192.168.1.103: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms This shows that 4 packets were sent, each with a Time To Live of 255ms. since my device is on the desk it took no measurable amount of ms to travel, which is shown in the Min Max and AVG. it is a good idea to have all devices on a network send information in a similar manner. If you leave the TTL on one device high, later as teh network becomes crowded, the extended packet life can cause random problems on the network which will be harder form someone else to troubleshoot.

[drusso 0]

we have the Eaton touch screen showing 128 for TTL The Control Logix is at 64 for TTL Is this going to cause network problems and how would I correct them. the control logix is showing the ethernet port is 100 full duplex thanks for the quick response dave

[ScottC 8]

For practical purposes, TTL is a count, not milliseconds. When you ping a device, it sets the TTL of the reply packet to some integer value, like 64, 128, or 255. As the reply packet makes its way back to the requester, the TTL value is decremented by one each time it passes through a router. If the TTL reaches 0, the packet dies. This countdown prevents packets from floating around the Internet indefinitely. The host device that is being pinged determines what the starting TTL will be. Apparently, the Eaton touchscreen starts at 128 and the ControlLogix starts at 64, and neither has to pass through a router to reach the requesting PC. The different TTLs between the two devices has nothing to do with their speeds and will not affect the network performance. Edited 10 Mar 2012 by ScottC