excessive nat to real networks

[gatonegro]

Our router a cisco 2621XM, is getting a lot of queries to real networks, and is has about 22,000 plus entries on the table. when it get to around 30,000 internet access slows down.

tcp 202.82.231.2:8059 10.36.41.20:2834 207.188.7.40:80 207.188.7.40:80
tcp 202.82.231.2:22355 10.36.41.20:2779 207.188.7.80:80 207.188.7.80:80
tcp 202.82.231.2:22350 10.36.41.20:2773 207.188.7.85:80 207.188.7.85:80
tcp 202.82.231.2:7212 10.36.41.16:4032 65.54.168.253:80 65.54.168.253:80
tcp 202.82.231.2:8496 10.36.41.16:2779 65.54.139.249:80 65.54.139.249:80
tcp 202.82.231.2:16206 10.36.41.52:4156 207.188.7.85:80 207.188.7.85:80
tcp 202.82.231.2:14163 10.36.40.98:2380 207.188.7.80:80 207.188.7.80:80
tcp 202.82.231.2:15774 10.36.41.95:1332 207.68.177.125:80 207.68.177.125:80
tcp 202.82.231.2:14203 10.36.41.52:3148 207.188.7.40:80 207.188.7.40:80
tcp 202.82.231.2:12115 10.36.40.98:4807 207.188.7.80:80 207.188.7.80:80
tcp 202.82.231.2:10067 10.36.41.9:3980 207.188.7.80:80 207.188.7.80:80

Need your advice, thanks in advance.