how to configured two routers cisco 1841 NAT configuration with steps 2026
Cisco 1841 NAT Configuration Between Two Routers (2026)
This example shows how to configure NAT (Network Address Translation) on two Cisco 1841 routers using static IP addressing.
Network Topology
PC1 ---- Router1 -------- Router2 ---- PC2
Fa0/0 S0/0/0 S0/0/0 Fa0/0
| Device | Interface | IP Address |
|---|---|---|
| PC1 | NIC | 192.168.1.10/24 |
| Router1 | Fa0/0 | 192.168.1.1 |
| Router1 | S0/0/0 | 10.0.0.1 |
| Router2 | S0/0/0 | 10.0.0.2 |
| Router2 | Fa0/0 | 192.168.2.1 |
| PC2 | NIC | 192.168.2.10/24 |
Requirements
2 × Cisco 1841 Integrated Services Router
Serial DCE/DTE cable
Console cable
2 PCs
Cisco IOS installed
Packet Tracer or real hardware
Step 1: Connect the Devices
Use:
Console cable → PC to Router console port
Serial cable → Router1 S0/0/0 to Router2 S0/0/0
Ethernet cable → PCs to Fa0/0 interfaces
Step 2: Configure Router1
Enter privileged mode:
Router> enable
Router# configure terminal
Configure FastEthernet Interface
Router(config)# interface fa0/0
Router(config-if)# ip address 192.168.1.1 255.255.255.0
Router(config-if)# no shutdown
Router(config-if)# ip nat inside
Router(config-if)# exit
Configure Serial Interface
Router(config)# interface s0/0/0
Router(config-if)# ip address 10.0.0.1 255.255.255.252
Router(config-if)# clock rate 64000
Router(config-if)# no shutdown
Router(config-if)# ip nat outside
Router(config-if)# exit
Step 3: Configure NAT on Router1
Create Access List
Router(config)# access-list 1 permit 192.168.1.0 0.0.0.255
Enable PAT (NAT Overload)
Router(config)# ip nat inside source list 1 interface s0/0/0 overload
This command allows all inside local addresses to share the serial interface IP address.
Step 4: Configure Static Route on Router1
Router(config)# ip route 192.168.2.0 255.255.255.0 10.0.0.2
Step 5: Configure Router2
Router> enable
Router# configure terminal
Configure FastEthernet Interface
Router(config)# interface fa0/0
Router(config-if)# ip address 192.168.2.1 255.255.255.0
Router(config-if)# no shutdown
Router(config-if)# exit
Configure Serial Interface
Router(config)# interface s0/0/0
Router(config-if)# ip address 10.0.0.2 255.255.255.252
Router(config-if)# no shutdown
Router(config-if)# exit
Step 6: Configure Static Route on Router2
Router(config)# ip route 192.168.1.0 255.255.255.0 10.0.0.1
Step 7: Configure PCs
PC1
IP Address : 192.168.1.10
Subnet Mask: 255.255.255.0
Gateway : 192.168.1.1
PC2
IP Address : 192.168.2.10
Subnet Mask: 255.255.255.0
Gateway : 192.168.2.1
Step 8: Save Configuration
On both routers:
Router# copy running-config startup-config
Step 9: Verify NAT
Check Interface Status
Router# show ip interface brief
Check NAT Translations
Router# show ip nat translations
Check NAT Statistics
Router# show ip nat statistics
Step 10: Test Connectivity
From PC1:
ping 192.168.2.10
From Router1:
ping 10.0.0.2
Important NAT Commands
| Command | Purpose |
|---|---|
ip nat inside | Marks inside interface |
ip nat outside | Marks outside interface |
access-list 1 permit | Defines inside network |
ip nat inside source list 1 interface s0/0/0 overload | Enables PAT |
show ip nat translations | Displays NAT table |
Expected Result
PC1 can communicate with PC2
Router1 translates private IP addresses using NAT overload
NAT table entries appear during ping traffic
Example NAT Translation Table
Inside global Inside local Outside local Outside global
10.0.0.1 192.168.1.10 192.168.2.10 192.168.2.10
Troubleshooting Commands
show running-config
show ip route
show controllers serial 0/0/0
show ip nat translations
debug ip nat
Notes
Use
clock rate 64000only on the DCE side.Always configure:
ip nat insideip nat outside
Verify serial interfaces are UP using:
show ip interface brief