RTC#show ip route
<output omitted>
C    172.16.0.0/16 is directly connected, Serial0
C    172.17.0.0/16 is directly connected, Serial1
C    172.18.0.0/16 is directly connected, Serial2
C    172.19.0.0/16 is directly connected, Serial3
R    172.20.0.0/16 [120/1] via 172.17.0.2, 00:00:02, Serial1
R    172.21.0.0/16 [120/1] via 172.19.0.2, 00:00:02, Serial3
*S   0.0.0.0 /0 S* is directly connected, Serial0
