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Inconsistent Network operation

We have a Cisco Catalyst 500 Ethernet Switch connected to a Cisco 871 Ethernet Access Router.

The network is basically 1 VLAN with approx. 10 Computer Hosts and 10 Commercial Printers.

The Vlan host IP addresses are static local IP numbers. (10.40.6.X).

I have tried to configure the router to dynamically NAT the hosts Static IPs with the Outside

interface IP address (FastEthernet 4) with overload. When I test the interface with SDM, between the

Ethernet 4 Global address, and the default static route IP addr.(the ISP default gateway) The SDM

sets up the ping, not to the gateway address but to the DNS and of course the ping fails.

If I manually set the ping from the FastEthernet to the default Gateway the ping is successful

The Router sometimes works well for a while and then suddenly cannot route to the internet. The configuration has not changed and I can verify the Running Configuration via both SDM and the IOS CLI. This inconsistency is

devastating. This configuration must be the most simple that one can implement. I have attached the running config. Is this a configuration error or is there a router hardware problem?

Hall of Fame Super Silver

Re: Inconsistent Network operation

Hello Duane,

first of all next time mask your public ip address (forgive me if you have already changed them)

I see this :

>>access-list 1 permit

you have denied from NAT the printers and then there is this line

I don't think the wildcard mask is the right one: it should be

decimal 75 is : 01001011

decimal 255 is : 11111111

only the second allows every device in not denied by previuos ACL lines to access the internet

Hope to help


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