I'm quite new to Cisco and I'm currently working on my CCNA. I recently had the opportunity to take a closer look at the following devices:
- Cisco 1841 ISR
- Cisco Catalyst 2950 24 port
- Cisco Aironet 1231AG
As a start, I wanted to replace my soho hardware and upgrade my home network to these devices. My ISP provides Internet connectivity through cable which is basically Fast Ethernet through the cable modem. The FastEthernet 0/1 is connected to the modem and acquires ip address through DHCP. The internal interface of the 1841 has a static ip address of 192.168.0.1/24. On the router I enabled the onboard dns server and enabled port address translation. The configuration file looks like the following:
Current configuration : 3253 bytes
service timestamps debug datetime msec
service timestamps log datetime msec
boot system flash c1841-adventerprisek9-mz.124-24.T1.bin
logging message-counter syslog
enable secret 5 $1$ZgH.$IeANuKYd/rNpxUuqXo6.k/
no aaa new-model
no ip dhcp use vrf connected
Everything works fine (I mean all the internal devices have Internet connectivity and CBAC works as expected, but these are not listed in the config). The problem I'm posting this is that when I add static NAT entries (in soho devices this is called port mapping) I can only reach internal services from an outside IP address. The problematic entry:
ip nat inside source static tcp 192.168.0.50 80 interface FastEthernet0/1 8080
This means that I can reach the web server on my internal network from another network on port 8080 but I cannot reach it from 192.168.0.0/24. Let's say that the outside address is 220.127.116.11, then from 192.168.0.50 or 192.168.0.10 I am unable to browse the homepage at 18.104.22.168:8080.
I read lots of forum threads and manuals but I can't see the reason for this happening. I had no such problem with soho devices like D-link or SMC.
I tried to make a "raw" connection with Putty to the port and outside IP address, but the router closes the connection ("Connection closed by remote host").
I also experienced an interesting effect with the router:
When I change the outside interface's MAC address to one that is on the inside network the communication with these devices fail. Again this is not a problem with most SOHO devices. Is there a way to isolate the inside and outside interfaces?
Any help would be greatly appreciated (the static NAT problem is of much higher importance), thank you in advance!
Please try this:
ip nat enable
ip nat enable
ip nat source list 1 interface FastEthernet0/1 overload
ip nat source static tcp 192.168.0.50 80 interface FastEthernet0/1 8080
This is the "NAT Virtual Interface Support" of the IOS which is used to Inside-to-Inside NAT.
This feature was introduced in version 12.3(14)T. I hope that your IOS supports it.
I hope that this is useful for you.