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NAT Translation IP usage

Last updated on December 23, 2018

        I'm new to cisco and currently studying for a certification, this is just my way of practicing what I learned.. Currently I'm in a standstill because I can't seem to understand what is happening, or maybe my NAT fundamentals is off. Anyways please refer to the topology I created via Packet Tracer
enter image description here CR running-config
!
!
!
interface GigabitEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 ip nat inside
 duplex auto
 speed auto
!
interface GigabitEthernet0/1
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface GigabitEthernet0/2
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface Serial0/3/0
 ip address 205.112.2.1 255.255.255.252
 ip nat outside
!
interface Serial0/3/1
 no ip address
 clock rate 2000000
 shutdown
!
interface Vlan1
 no ip address
 shutdown
!
ip nat pool mypool 172.16.2.1 172.16.2.31 netmask 255.255.255.224
ip nat inside source list 50 pool mypool overload
ip classless
!
ip flow-export version 9
!
!
access-list 50 permit 192.168.1.0 0.0.0.255
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end
ISP running-config
interface GigabitEthernet0/0
 ip address 210.125.35.1 255.255.255.0
 duplex auto
 speed auto
!
interface GigabitEthernet0/1
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface GigabitEthernet0/2
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface Serial0/3/0
 ip address 205.112.2.2 255.255.255.252
 clock rate 64000
!
interface Serial0/3/1
 no ip address
 clock rate 2000000
 shutdown
!
interface Vlan1
 no ip address
 shutdown
!
ip classless
ip route 0.0.0.0 0.0.0.0 205.112.2.1 
!
ip flow-export version 9
!
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end
Now, CR is my company router, connected via serial interface, also this is where i put my NAT configuration. ISP's is just a static route back to CR for ping purposes. What i did to verify this setup is via ping on PC0/PC1/PC2 to Server0 however it is unreacheable (yep understandable because CR has not route to 210.125.35.0 network) but considering NAT was configured on that router i expected it to be translated via the public IP and route it, at this point im really confused. Now another test i did was to ping the 205.112.2.2 interface on ISP router it boom it translated (confirmed via show ip nat translation). At this point im sure im missing something because im really confused at this point.. Can somebody help me clear things up? EDIT As @Ron Maquin said, it is a routing problem, i added a default route, but the nat translation is incrementing when i do continuous ping from PC0. As what i know, it will just reuse the assigned port to the translated IP (in this case PC0). Please correct me if im wrong, refer also to the show ip nat translation output
CR#show ip nat translations 
Pro  Inside global     Inside local       Outside local      Outside global
icmp 172.16.2.1:27     192.168.1.2:27     210.125.35.110:27  210.125.35.110:27
icmp 172.16.2.1:28     192.168.1.2:28     210.125.35.110:28  210.125.35.110:28
icmp 172.16.2.1:29     192.168.1.2:29     210.125.35.110:29  210.125.35.110:29
icmp 172.16.2.1:30     192.168.1.2:30     210.125.35.110:30  210.125.35.110:30
icmp 172.16.2.1:31     192.168.1.2:31     210.125.35.110:31  210.125.35.110:31
icmp 172.16.2.1:32     192.168.1.2:32     210.125.35.110:32  210.125.35.110:32
icmp 172.16.2.1:33     192.168.1.2:33     210.125.35.110:33  210.125.35.110:33
icmp 172.16.2.1:34     192.168.1.2:34     210.125.35.110:34  210.125.35.110:34
icmp 172.16.2.1:35     192.168.1.2:35     210.125.35.110:35  210.125.35.110:35
icmp 172.16.2.1:36     192.168.1.2:36     210.125.35.110:36  210.125.35.110:36
icmp 172.16.2.1:37     192.168.1.2:37     210.125.35.110:37  210.125.35.110:37
icmp 172.16.2.1:38     192.168.1.2:38     210.125.35.110:38  210.125.35.110:38
icmp 172.16.2.1:39     192.168.1.2:39     210.125.35.110:39  210.125.35.110:39
icmp 172.16.2.1:40     192.168.1.2:40     210.125.35.110:40  210.125.35.110:40
icmp 172.16.2.1:41     192.168.1.2:41     210.125.35.110:41  210.125.35.110:41
icmp 172.16.2.1:42     192.168.1.2:42     210.125.35.110:42  210.125.35.110:42
icmp 172.16.2.1:43     192.168.1.2:43     210.125.35.110:43  210.125.35.110:43
icmp 172.16.2.1:44     192.168.1.2:44     210.125.35.110:44  210.125.35.110:44
icmp 172.16.2.1:45     192.168.1.2:45     210.125.35.110:45  210.125.35.110:45
icmp 172.16.2.1:46     192.168.1.2:46     210.125.35.110:46  210.125.35.110:46
icmp 172.16.2.1:47     192.168.1.2:47     210.125.35.110:47  210.125.35.110:47

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