update route table 

Gateway of last resort is 192.168.30.1 to network 0.0.0.0

C    192.168.30.0/24 is directly connected, FastEthernet0/0
S    192.168.15.0/24 [1/0] via 192.168.20.2
S    192.168.10.0/24 [1/0] via 192.168.20.2
C    192.168.11.0/24 is directly connected, FastEthernet0/1.1
C    192.168.20.0/24 is directly connected, FastEthernet0/1.10
S*   0.0.0.0/0 [1/0] via 192.168.30.1
               is directly connected, FastEthernet0/0
CiscoCurious# 

CiscoCurious#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
CiscoCurious(config)#no ip default-gateway 203.1.233.220
CiscoCurious(config)#no ip route 0.0.0.0 0.0.0.0 192.168.20.2
CiscoCurious(config)#no ip route 0.0.0.0 255.255.255.0 192.168.20.2
CiscoCurious(config)#

Gateway of last resort is 192.168.30.1 to network 0.0.0.0

C    192.168.30.0/24 is directly connected, FastEthernet0/0
S    192.168.15.0/24 [1/0] via 192.168.20.2
S    192.168.10.0/24 [1/0] via 192.168.20.2
C    192.168.11.0/24 is directly connected, FastEthernet0/1.1
C    192.168.20.0/24 is directly connected, FastEthernet0/1.10
S*   0.0.0.0/0 [1/0] via 192.168.30.1
               is directly connected, FastEthernet0/0
CiscoCurious#