Driver package installed with no problems on a DS412+ (r8152-cedarview-2.17.1-2_6.2.spk). ASUS C2500 links with 2.5 GBit/s with the switch. However, actual speed is in the range of 80 to 90 MB/s. Speed measured with iperf shows appr. 800 MBit/s. Built-in LAN has higher performance.

ASUS C2500:

iperf -c 192.168.2.16 -p 5001 -P8

Client connecting to 192.168.2.16, TCP port 5001
TCP window size: 16.0 KByte (default)

[ 2] local 192.168.2.33 port 59064 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/261)
[ 3] local 192.168.2.33 port 59062 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/240)
[ 5] local 192.168.2.33 port 59080 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/252)
[ 7] local 192.168.2.33 port 59104 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/250)
[ 1] local 192.168.2.33 port 59116 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/233)
[ 8] local 192.168.2.33 port 59090 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/164)
[ 4] local 192.168.2.33 port 59086 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/140)
[ 6] local 192.168.2.33 port 59114 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/245)
[ ID] Interval Transfer Bandwidth
[ 6] 0.0000-10.0006 sec 150 MBytes 126 Mbits/sec
[ 2] 0.0000-10.0034 sec 77.0 MBytes 64.6 Mbits/sec
[ 8] 0.0000-10.0052 sec 105 MBytes 87.8 Mbits/sec
[ 7] 0.0000-10.0077 sec 239 MBytes 200 Mbits/sec
[ 4] 0.0000-10.0970 sec 109 MBytes 90.7 Mbits/sec
[ 5] 0.0000-10.1815 sec 25.8 MBytes 21.2 Mbits/sec
[ 1] 0.0000-10.2165 sec 132 MBytes 108 Mbits/sec
[ 3] 0.0000-10.2202 sec 63.0 MBytes 51.7 Mbits/sec
[SUM] 0.0000-10.2203 sec 900 MBytes 739 Mbits/sec

Built-In LAN:

iperf -c 192.168.2.16 -p 5001 -P8

Client connecting to 192.168.2.16, TCP port 5001
TCP window size: 16.0 KByte (default)

[ 3] local 192.168.2.33 port 47294 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/254)
[ 2] local 192.168.2.33 port 47314 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/259)
[ 6] local 192.168.2.33 port 47298 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/260)
[ 7] local 192.168.2.33 port 47348 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/158)
[ 5] local 192.168.2.33 port 47334 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/246)
[ 4] local 192.168.2.33 port 47350 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/142)
[ 1] local 192.168.2.33 port 47330 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/258)
[ 8] local 192.168.2.33 port 47366 connected with 192.168.2.16 port 5001 (icwnd/mss/irtt=14/1448/99)
[ ID] Interval Transfer Bandwidth
[ 8] 0.0000-10.0068 sec 146 MBytes 122 Mbits/sec
[ 1] 0.0000-10.0076 sec 131 MBytes 110 Mbits/sec
[ 2] 0.0000-10.0111 sec 145 MBytes 122 Mbits/sec
[ 3] 0.0000-10.0066 sec 150 MBytes 126 Mbits/sec
[ 5] 0.0000-10.0104 sec 141 MBytes 118 Mbits/sec
[ 7] 0.0000-10.0070 sec 143 MBytes 120 Mbits/sec
[ 6] 0.0000-10.0092 sec 143 MBytes 120 Mbits/sec
[ 4] 0.0000-10.0209 sec 128 MBytes 107 Mbits/sec
[SUM] 0.0000-10.0213 sec 1.10 GBytes 943 Mbits/sec

Too bad. Maybe the 412+ is too old for these speeds...