Strange ping/connectivity problem

Question

We have a 5300 + silabs product, and it does not have any DHCP support code. I can ping it with a direct cable connection from PC. I can ping it through my switch A. There can be multiple devices in the same switch A belonging to a network, say 192.168.1.x. My arp table if fine till this point. If I connect this switch to another switch B belonging to an existing large network with lot of devices, all hell breaks loose. 5300 replies for the first ping, and then it times out. Sometimes, it doesn’t even reply for the first ping. If I see THE arp table, I can see that the MAC of 5300 is replaced with something else, and the gateway I entered in 5300 is also present with the same MAC, even though that gateway IP is not a valid IP or valid device! If I change the gateway in 5300 to 0.0.0.0, it doesn’t help. If I replace my 5300 device with another thirdparty device which uses realtek nw chip, with same IP and MAC, that device works fine, and pings well. If I replace 5300 device with a laptop, then the laptop replies for the ping correctly. If I remove the cable connection between this switch and the other network, then the problem disappears. That network has multiple network addresses, 192.168.1.x and 2.xs connected using 2 switches and nothing else, to my knowledge. No IP clash or MAC clash, since I can replace my device with another third party device with same MAC/IP as mentioned before, then it pings fine. If I do not use switch A, and just plug 5300 device into switch B network, the result is same. Some times, if 5300 initiates a connection to a specific PC in switch B, then from that machine, 5300 can be pinged. Broadcasts from 5300 can also be received in all PCs connected in switch B. I have tried clearing arp table before pinging, specially when I see the arp table being filled with wrong MAC value of 5300 ie: MAC that does not belong to 5300. In short, 5300 doesn’t ping correctly in some network, with unknown /many devices !! . But my 5300 device works correctly with 3 or 4 devices in switch A, and can communicate with external word through a gateway also. What could be wrong? Can 5300 negotiate speed with any 10/100/1000 switch / network device? I have tested it with 10/100 and it works fine.

rm69 · Answer

I have also posted this at tomshardware.com/answers/id- … issue.html since the answers from wiznet are generally late, if at all I get them. Got one reply from Tomshardware.com. He suggested that the issue could be arp poisoning. Is there any reason why a similar device (non wiznet serial-ethernet device) with same MAC and IP doesn’t get affected? wiznet ping reply is hardware processed, and does this have something to do with the issues?

hjjeon0608 · Answer

Hi, rm69. I think thirdparty device, PC or laptop can ping because they use DHCP. If switch A and B has static IP as 192.168.1.x or 192.168.2.x, there must not be pinged every device because 192.168.x.x is private IP. So switches could have public IP you don’t know. So, I recommend to use DHCP, and WIZ200WEB has W5300 and DHCP sample code. [url]http://www.wiznet.co.kr/UpLoad_Files/ReferenceFiles/WIZ200WEB_FW_V140.zip[/url] Try to test with this code and reply again please. If partner has 10/100/1000 based speed, W5300 can connect to the partner. But speed is 10/100 not 1000 because W5300 has 10/100 based speed. i.e. if partner has only 1000 based speed, W5300 cannot connect. Best regards.

rm69 · Answer

Thanks, hjjeon0608 for the reply. Please go through the comments and advice. Actually, I have mentioned that the devices from same network cannot ping wiznet. (ie: if wiznet address is 192.168.1.5 then 192.168.1.x devices are not able to ping. That was the quesiton!). I do not require DHCP at all. static ip address onlyis required. But, when wiznet device is connected to a specific network, ping works only once. When I posted this in Tom’s hardware.com. I got the response that, this could be because of arp poisoning. Please check my link. Wiznet mac address is in such a network is somehow being changed. I have tested wiznet using a couple of different makes of switches of speed 10/100/1000, and it works fine. But I have found some laptops with 10/100/1000 not working. I needed to confirm that, wiznet can work in all 10/100/1000 environments. Speed would be 100 mbps, but what is important is to be able to connect and establish 100 mpps speed without errors.

rm69 · Answer

Thank you for the reply. Currently, we are sending data to a specific peer, and from that peer, pinging seem to be working, but with issues. Will create a new subject on that, for clarity 2 I understand that you cannot guarantee connection with all the devices. But I can see that, it would connect with normal 10/100/1000 ports, and that would be quite sufficient for all purposes. I was merely asking if there are any documented incompatibilities with auto-negotiation with 10/100/1000, and if there is anything specific that we should be aware of. Thanking you again. We feel supported and re-assured when questions are answered, or replied to.

hjjeon0608 · Answer

Hi, rm69. I contemplated about No.1 problem. I think arp table of router or switch is changed because there are same IP. So first, W5300’s MAC address is written at ARP table and then another device send ARP packet so MAC address could be changed. And it is looked like ARP poison. The network are very large so it could be happened. But I still wonder why ping still works with other device(e.g. laptop). You may believe W5300 has problem, but the product is launched long time ago and it does not have such problem. And packet sent by W5300 is standard so I recommend to use like dummy hub for capturing ping packet between A network and B network. If you can, it help to solve the problem a lot. Best regards.