how do you connect a cisco router to the internet through a cable modem/ router gateway

[breynold76]

I have searched on here but can't find the exact answer i am looking for. I have a cisco 1760 router and a 2950 switch. The router has an ethernet wic card added so i have two ethernet connections available. I would like to connect the cable modem gatway to the router through one of the ethernet connections on the router and then to the switch. I cannot seem to get this setup to work. There are several different ways i have seen posted to accomlish this. dhcp, no dhcp, creating a seperate network, and giving the e0/0 an ip address within the range of the cable gateways network addresses. None of this has worked. Can anybody post the commands that need to be entered on the router to make this possible?

[breynold76]

I made the changes to the router.

The computer is receiving an ip address from the router now.

The computer can now ping the modem and the router.

The router can now ping the pc and the modem.

But there is no internet access.  just to make sure i got this right here is the show run and the show ip int brief.

R1#show ip int brief

Interface                  IP-Address      OK? Method Status                Protocol

Ethernet0/0                unassigned      YES TFTP   administratively down down

FastEthernet0/0            unassigned      YES manual up                    up

FastEthernet0/0.1          192.168.1.1     YES TFTP   up                    up

FastEthernet0/0.100        192.168.0.101   YES TFTP   up                    up

Serial1/0                  unassigned      YES TFTP   administratively down down

Serial1/1

R1#show run

Building configuration...

Current configuration : 1536 bytes

!

! Last configuration change at 01:36:37 UTC Thu Jul 31 2008

!

version 12.3

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname R1

!

boot-start-marker

boot-end-marker

!

no logging console

!

mmi polling-interval 60

no mmi auto-configure

no mmi pvc

mmi snmp-timeout 180

no aaa new-model

ip subnet-zero

ip cef

!

!

ip dhcp excluded-address 192.168.1.0 192.168.1.99

!

ip dhcp pool MY_LAN

   network 192.168.1.0 255.255.255.0

   default-router 192.168.1.1

   dns-server 192.168.0.1

!

ip name-server 24.217.0.5

ip name-server 8.8.8.8

ip name-server 192.168.0.1

no ftp-server write-enable

!

!

!

!

interface Ethernet0/0

no ip address

shutdown

half-duplex

!

interface FastEthernet0/0

no ip address

speed auto

!

interface FastEthernet0/0.1

description ##my lan##

encapsulation dot1Q 1 native

ip address 192.168.1.1 255.255.255.0

ip nat inside

!

interface FastEthernet0/0.100

description ##internet##

encapsulation dot1Q 100

ip address 192.168.0.101 255.255.255.0

ip access-group MY_WAN in

ip nat outside

!

interface Serial1/0

no ip address

shutdown

!

interface Serial1/1

no ip address

shutdown

!

ip nat inside source list MY_LAN interface FastEthernet0/0.100 overload

ip classless

no ip http server

!

ip access-list standard MY_LAN

permit 192.168.1.0 0.0.0.255

!

ip access-list extended MY_WAN

permit tcp any any established

deny   tcp any any

permit ip any any

!

!

line con 0

password cisco

login

line aux 0

line vty 0 4

password cisco

login

!

!

end

[Bilal Nawaz]

Hello Bernard, are you able to do the tftp now?
What happens when you ping 8.8.8.8 from the router?

As long as we can get a copy of that image for now :-)

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[Richard Burts]

I am glad that the router and the PC are now communicating. I agree that this is an important step in being able to get a copy of the image file and to use that to repair the first router which now has no image.

It is important to check to see if the router has access toward the Internet further than the cable modem. The ping to 8.8.8.8 is a good first step. Perhaps you could also post the output of show ip route from the router?

HTH

Rick

[Richard Burts]

Do not be concerned that the subinterfaces still show up in the output of showIP interface brief. This is normal behavior. But the subinterfaces are not doing anything.

If this set up does not succeed in getting an address from the cable modem it might be helpful to run the debuts for dhcp and post the output.

HTH

Rick
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[Bilal Nawaz]

Please configure your default route

Conf t
!
Ip route 0.0.0.0 0.0.0.0 192.168.0.1

Then try ping again

Hope this helps

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[breynold76]

I can ping 8.8.8.8 successfully from both the cisco router and the computer. The computer says that it has Internet access but cannot connect to any web pages but, The magic jack phone is connected to the cisco switch and is working.

[Bilal Nawaz]

Hello Bernard, thats great

This is Because of the dns I think

ip dhcp pool MY_LAN
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
dns-server 192.168.0.1

Instead of this : dns-server 192.168.0.1
Try this: dns-server 8.8.8.8

Hope this helps

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[Bilal Nawaz]

You will need to renew your dhcp lease by disconnecting and reconnecting

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[breynold76]

That worked I now have internet access on the computer through the cisco router and switch.

[Bilal Nawaz]

Awesome! so at the same time we've managed to fix it all :-) (sort of)

We're recovering the router now right?

Please rate useful posts and remember to mark any solved questions as answered. Thank you.

[breynold76]

yes

[Bilal Nawaz]

Okay, so we need to start off by plugging the rommon router in to VLAN 1 on the switch.

and just see if these commands are available - the lines in bold need to be changed to our scenario...

No spaces - case sensitive

:

rommon 1 > IP_ADDRESS=192.168.1.100
rommon 2 > IP_SUBNET_MASK=255.255.255.0
rommon 3 > DEFAULT_GATEWAY=192.168.1.1
rommon 4 > TFTP_SERVER=[YOUR TFTP SERVER IP]
rommon 5 > TFTP_FILE=c1700-EXAMPLE.bin
rommon 6 > TFTP_CHECKSUM=0
rommon 7 > tftpdnld

IP_ADDRESS: 192.168.1.100           
           IP_SUBNET_MASK: 255.255.255.0
           DEFAULT_GATEWAY: 192.168.1.1
           TFTP_SERVER: X.X.X.X
           TFTP_FILE: c1700-EXAMPLE.bin

     Invoke this command for disaster recovery only.
     WARNING: all existing data in all partitions on flash will be lost!
     Do you wish to continue? y/n:  [n]:  y

     Receiving c1700-EXAMPLE.bin from x.x.x.x !!!!!!!!!!!!!!!!!!!!!!!!!!
     File reception completed.
     Copying file c1700-EXAMPLE.bin to flash.
     Erasing flash at 0x607c0000
     program flash location 0x60440000
     rommon 9 >reset

Hope this helps

Please rate useful posts and remember to mark any solved questions as answered. Thank you.

[breynold76]

I got it to take all the commands but this is what i come up with when done.

          IP_ADDRESS: 192.168.1.100

      IP_SUBNET_MASK: 255.255.255.0

     DEFAULT_GATEWAY: 192.168.1.1

Poorly formed ip address for variable TFTP_SERVER

Illegal tftp server IP address.

usage: tftpdnld [-r]

  Use this command for disaster recovery only to recover an image via TFTP.

  Monitor variables are used to set up parameters for the transfer.

  (Syntax: "VARIABLE_NAME=value" and use "set" to show current variables.)

  "ctrl-c" or "break" stops the transfer before flash erase begins.

  The following variables are REQUIRED to be set for tftpdnld:

            IP_ADDRESS: The IP address for this unit

        IP_SUBNET_MASK: The subnet mask for this unit

       DEFAULT_GATEWAY: The default gateway for this unit

           TFTP_SERVER: The IP address of the server to fetch from

             TFTP_FILE: The filename to fetch

  The following variables are OPTIONAL:

          TFTP_VERBOSE: Print setting. 0=quiet, 1=progress(default), 2=verbose

      TFTP_RETRY_COUNT: Retry count for ARP and TFTP (default=7)

          TFTP_TIMEOUT: Overall timeout of operation in seconds (default=7200)

         TFTP_CHECKSUM: Perform checksum test on image, 0=no, 1=yes (default=1)

  Command line options:

   -r: do not write flash, load to DRAM only and launch image

rommon 33 >

[breynold76]

Disregard the last post. that was my fault i put some spaces in where i should not have. It is receiving the file now.

[Bilal Nawaz]

That's good! Once that is done we should be able to boot from it hopefully.

Thanks for updating us with progress

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