Cisco 1720 Router

Posted on 2005-03-04
Medium Priority
Last Modified: 2013-11-29
I am never set up a Cisco router from scratch before.  I have both ethernet ports setup one with a local lan ip & the other with a public ip. When I telnet into the router, I can ping www.google.com with success.  If I set my pc to use the router as a gateway & ping google from a command prompt, it returns my routers lan ip as responding. Any clues as to what might be wrong??

Thanks in advance!
Question by:8lackd0g
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LVL 10

Expert Comment

ID: 13463977
Can you post your router config?  Also, please advise if when ping a public IP address like from your PC you get a reply.
LVL 15

Accepted Solution

getzjd earned 1000 total points
ID: 13463995
You need a default Route  and NAT/PAT
For default route

Ip Route S0  

 Assuming S0 is your internet connection.

You will also need to configure PAT
Router#conf t

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#interface ethernet0

Router(config-if)#ip nat inside

Router(config-if)#interface serial0

Router(config-if)#ip nat outside

Router(config)#ip nat inside source list 1 interface serial0 overload

Router(config)#access-list 1 permit   *** change this to suit your IP scheme to permit your network to access the interface

That should get you going.

If you have any other questions about configuring, you may want to post your config.. just makes sure to XXXX out your passwords .

Author Comment

ID: 13464174
Thanks!! I added your two last suggestions & it works perfectly!

Router(config)#ip nat inside source list 1 interface ethernet0 overload

Router(config)#access-list 1 permit

I also have a few entries that I have not seen before:

ip virtual-reassembly
no cdp enable (if I try to enable, I get an error "service not running")
no service password-encryption (does this hide my router password?)

Should this be changed? -- snmp-server community public RO

Nice router for $300 bucks.  Came with 12.3, WIC Fast Ethernet & more memory than the 1721!
LVL 15

Expert Comment

ID: 13464212
If i were you I would issue the command
Service password-encryption  to encrypt your passwords.  

This link here will explain what the CDP means


The SNMP community can be changed to your liking, however you will probably never use it.  You can use SNMP to do things like monitor utilization of your interfaces from your desktop etc.

Here is an app that can do such a thing http://www.paessler.com/prtg

Virtual-Reassembly or VFR  can be used to  help against some types of attacks.  Rather than reinvent the wheel and type out a long description, I will let cisco do the explaining :)  


Author Comment

ID: 13465732
Dam! Wish I could have increase the points awarded. Thank you very much!

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