Hi, [We captured the traffic with a Mac Book Pro directly connected to the router.  We conducted a ping sweep in two configurations: Our understanding is that the MBP offloads TCP Checksums to the network interface so that is why WireShark is flagging the Checksum errors but we were able to successfully transmit/receive packets up 1472 bytes.  using the DF, Sweep, and Size options. We can connect via both a TP-Link Router and Apple Airport Base Station but have not yet tried a direct connecting from Client Computer to Cable modem as the both the Apple Airport and TP-Link router function without any issues Yes.  We've tried with both PC (Windows XP) and Mac (10.6.5) computers with the same issues Yes.  We also tried yahoo .  We discovered google apparently has limitations on their ICMP responses, I'm guessing because everyone "pings" them.  So the ICMP responses range from minimum of 26 Bytes to a maximum of 72 bytes.  Yahoo does not exhibit this behavior and we get responses from 9 Bytes to 1472 Bytes without any problem. We are experiencing the issue on both HTTP and HTTPS So an overview: Appeciate your insight.  We originally duplicated the Wifi router WAN port MAC address ,  in case the ISP had locked the cable modem to this address.  However,  we subsequently found out that the ISP does not lock the CM to the MAC address so this was unnecessary.  We removed the manually set MAC address and are still experiencing the same issue. We are currently using a Cable Modem, so there isn't a PPPoE configuration to setup. Further testing:  We can Ping from 64 to 1472 bytes via setting the ICMP  packet size on both the MAC and PC.  Pings work both directly across  the cable modem and using an Airport Base Station from both the MAC and PC Clients.  Pings also work correctly across the Cisco 3620 router .  Although sometimes it appears there is some additional latency which is odd. Mac or PC Client <—Directly Connected ---> Cisco 3620 <---Directly Connected ----> Motorola Cable Modem Mac or PC Client  <—Directly Connected ---> Apple Airport Base Station <---Directly Connected ----> Motorola Cable Modem In both setups the cables between the points are the same and in the case of the Airport Base Station we also tested via Wifi.  That said, after additional testing it appears that some web pages do  try to load but is either very slow to load or times out.  I would  expect this kind of pattern if there was a duplex mismatch but after  setting the Speed/Duplex to 10 half on both interfaces and watching the  interface counters....the interfaces are clean.  Meaning no giants or  runts detected on either interface as would be expected with a duplex  mismatch. We also turned on all possible TCP debugging with no errors.  Show IP  NAT Trans also shows the NAT translations tables being updated.   Lastly  we checked Show Proc CPU and looked for areas of high utilization but  the only process that was using slightly elevated CPU was ARP.  Not sure  if this is normal but ARP was running between 10-13% CPU utilization. Did a show debug all and watched all the conversations and status  messages for a while so we could buffer them into hyperterminal but  didn't see/find anything significant. Thanks ... View more

Hi, Sorry about the delay in responding as I still am struggling with this issue. The notification of a response to this thread ended up in my spam folder. In any case, ICMP seems to be moving along ok, but tcip seems squeezed. I did a little housekeeping and am attaching some more files. Thanks a heap, ... View more

Ok, I will try it from  the reformat side/recopy first. This was supposedly a new card but you never know. Is there any chance that the simm image will expand slightly diferently in flash memory then Simm? The size in bytes is the same on both cards. I backed up the image before the first copy to my TFTP server plus I have another IOS that I can throw on the hardrive in the worst case. Would a running config  copy be a better comparison as it would already be uncompressed? The router boots and has been running from the simm source with no known issues ... View more