I am having a strange problem connecting Wireless ADSL2+ modem to an 8-port D-Link DES1008D switch. If I connect the Wireless ADSL2+ modem to my 8-port switch with a short 1-meter long CAT5 cable, then it works well without any problem. No losses shown on ping (no losses even with 65500 packets, using ping –l 65500 command). But if I use a long CAT5 cable of around 12 meters, then it does not connect at all. Light on the 8-port switch is not stable and it keeps on blinking and ping just totally fails. I tried changing cable too using CAT6 (assuming that first CAT5 cable may be defective) and then I even used another 8-port switch (one of same D-Link model and one other of Intex make) but no difference, same error. I also tried 4 different ADSL2+ modems (2 wired and 2 wireless) but same error on all of them.
Now strangely, if I connect the same Wireless ADSL2+ modem directly to my computer without any switch in-between using same cable, then it works. I even joined both the cables to make it a total of around 25-meter length, then also it worked without any losses. Means without switch, no length issues while connecting Wireless ADSL2+ modems to PC.
I tried using straight and crossover cables but same results. Switch is unmanaged so it is supposed to handle both types of cables but still I tried just to be sure.
Now one more thing, I replaced 8-port D-Link DES1008D switch with a 16-port D-Link DGS1016D switch, then it worked. So it means, that 8-port switches cannot be used to connect Wireless ADSL2+ modems for long lengths? Also 16-port switch is a Gigabit switch as compared to 8-port 10/100M switch so that will make any difference on this scheme? If so, then very strange because 8-port D-Link DES1008D switches connect 2 PCs over up to 90-100 meters then why not take the Wireless ADSL2+ modems to just 12 meters?
All my IP addresses are static; I am not using any DHCP in any hardware.
Please suggest if I am doing something wrong or how can I connect the Wireless ADSL2+ modems with a 12-meter long cable. I need a switch because I need my other 2 PCs on wireless network too which are connected to same switch. I do not want to invest into a new 16-port switch (which connects it) because just for 3 PCs having a 16-port switch at home is not a wise option.