Can't ping form ISP router To Cisco router

[a-2011]

Hi,

For some reason I can't ping back my inernal network>

I've configured my network as follow:

When I ping form PC-1 to:

CSB250 -> Works 

C877 -> Works

ISP Router -> Works

and vice versa, except whe ping form ISP router OR PC-2 to any device the C877 router, the switch or the PC-1 -> Not woking!!

what it is missing?

[umeshpathak]

If i understand correctly You can ping all the device is pinging from PC-1.Also when ping from PC-2 ,you can ping ISP router both interface and c877 F0 but nothing after that?Correct?

Looking at your config you don't have 1 to 1 static nat but using PAT,thats the reason it is not working.If you want access of the devices you have to configure 1:1 NAT translation.

[a-2011]

when pining form PC-2 I can only ping the ISP, but when pining from PC-1 i can reach ISP router and PC-2

[MHM Cisco World]

ISP router have one link 
192.168.2.0/24 and you connect PC have also subnet 192.168.2.0 !!
that I think issue here 

[a-2011]

only one subnet and the pc is connect via wifi

[MHM Cisco World]

change the PC-2 subnet and check again 

[a-2011]

the ISP router is not configurable. The only thing i cand is set the ip. with one subnet only 255.255.255.0

[mlund]

@umeshpathak has the answer. You have configured nat overload. So when packet from inside goes through c877w it is doing a nat tranlation and is inserted this translaton in the table, that will enable return traffic to pass, and that's why ping works from inside. You can verify this with the command

show ip nat translation

this command must be entered within 5 minutes( i think) because of flush timer. When you try to ping from outside there are no matching translation entry in the table, and therefore ping fails from outside.

[a-2011]

what should I do?

[umeshpathak]

What is your requirement?Give me more details what you need hopefully i can help,

[mlund]

That depends on your goal. What are you going to achieve?

Is the goal to just get the ping to work, then remove the nat statements. If you need the nat, then you have to configure static nat statements.

[danielmason794 · Accepted solution]

If you are unable to ping from your ISP router to your Cisco router, there may be several reasons for the issue. Here are some troubleshooting steps you can try to resolve the issue:

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1. Verify connectivity: Make sure that the cables are securely connected between the ISP router and the Cisco router and that both devices are powered on. You can also try swapping cables to rule out a faulty cable as the cause of the issue.

2. Check firewall and security settings: Ensure that the firewall and security settings on both the ISP router and the Cisco router are not blocking the ICMP (ping) packets.

3. Configure the IP address: Verify that the IP addresses for both the ISP router and the Cisco router are properly configured and in the same subnet.

4. Disable any virtual interfaces: If there are virtual interfaces configured on the Cisco router, try disabling them and see if you can ping the router.

5. Disable ACLs: If there are Access Control Lists (ACLs) configured on the Cisco router, try disabling them and see if you can ping the router.

6. Update the IOS: If the issue persists, consider updating the IOS (operating system) on the Cisco router to the latest version.

7. Contact the support team: If you are still unable to ping from the ISP router to the Cisco router after trying these troubleshooting steps, consider reaching out to the support team for further assistance.