ifconfig down/up は、どちらの機材で行っても一時的に改善するようです。

パケットロスが無いときは、上り下りとも 10 Mbps 以上は出ます。

【パケットロス時】
64 bytes from 192.168.10.8: seq=0 ttl=64 time=12.700 ms
64 bytes from 192.168.10.8: seq=1 ttl=64 time=73.981 ms
64 bytes from 192.168.10.8: seq=2 ttl=64 time=194.353 ms
64 bytes from 192.168.10.8: seq=3 ttl=64 time=55.669 ms
64 bytes from 192.168.10.8: seq=5 ttl=64 time=22.883 ms
64 bytes from 192.168.10.8: seq=6 ttl=64 time=75.214 ms
64 bytes from 192.168.10.8: seq=9 ttl=64 time=50.540 ms

【down/up 3分後】
64 bytes from 192.168.10.8: seq=0 ttl=64 time=2.761 ms
64 bytes from 192.168.10.8: seq=1 ttl=64 time=4.214 ms
64 bytes from 192.168.10.8: seq=2 ttl=64 time=3.028 ms
64 bytes from 192.168.10.8: seq=3 ttl=64 time=2.934 ms
64 bytes from 192.168.10.8: seq=4 ttl=64 time=3.490 ms
64 bytes from 192.168.10.8: seq=5 ttl=64 time=2.916 ms
64 bytes from 192.168.10.8: seq=6 ttl=64 time=3.717 ms
64 bytes from 192.168.10.8: seq=7 ttl=64 time=8.169 ms
64 bytes from 192.168.10.8: seq=8 ttl=64 time=163.032 ms
64 bytes from 192.168.10.8: seq=9 ttl=64 time=4.076 ms