Cisco 1720 will not connect to the internet via cable modem

Posted on 2008-11-05
Last Modified: 2012-08-13
I cannot figure out why this router will not connect to the internet. I can ping the default gateway and the ISP static IP however I cannot get any traffic to route.

Here is the IP information.


Below is the current config in the router

Building configuration...

Current configuration : 989 bytes


version 12.2

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption


hostname aplus


logging queue-limit 100

enable secret 5 $1$k4dO$m3yehiDWG0lpIpaki.Cdg.

enable password cisco


memory-size iomem 25

ip subnet-zero

no ip routing








interface Ethernet0

 description COX Business Internet

 ip address

 ip nat outside

 no ip route-cache

 no ip mroute-cache



interface FastEthernet0

 ip address

 ip nat inside

 no ip route-cache

 no ip mroute-cache

 speed auto



ip nat inside source list 1 interface Ethernet0 overload

ip classless

ip route

ip http server

ip http authentication local




access-list 1 permit

access-list 2 permit


snmp-server community public RO

snmp-server enable traps tty


line con 0

line aux 0

line vty 0 4

 password cisco




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Question by:lostvoid
    LVL 43

    Accepted Solution

    You have "no ip routing" in the config.

    conf t
    ip routing

    Expert Comment

    How are your pc's getting ip? Also, I dont see your DNS entries in the config....

    config t
    ip name-server
    ip name-server
    ip dhcp relay information option

    int fastethernet0
    ip helper-address x.x.x.x (dhcp server ip address)

    Author Closing Comment

    Thanks, I'm not too great with Cisco configurations yet. I figured it had to be something simple

    Author Comment

    Thanks, that got me up and running, I knew it had to be something simple.

    The SBS 2003 server will be handling DHCP and DNS assignments will be handled through the server as well

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