IF your having slow network on your Centos box best you check for TCP offloading issues.
tcpdump -i eth1 -v -nn| grep -i incorrect
If you get a lot of
103.4.122.47.22 > 103.4.123.36.53996: Flags [P.], cksum 0xc3d6 (incorrect -> 0xd4eb), seq 7496:7592, ack 9003, win 559, length 96
then try
ethtool -K eth0 rx off tx off sg off tso off ufo off gso off gro off lro off
