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 used putty this time instead of hyperterminal so hopefully it is easier to read.

Building configuration...

Current configuration : 1196 bytes

!

! Last configuration change at 03:58:20 UTC Sun Mar 3 2002

! NVRAM config last updated at 05:35:04 UTC Sun Mar 3 2002

!

version 12.3

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname Router

!

no logging console

!

no aaa new-model

ip subnet-zero

!

!

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 8.8.4.4 8.8.8.8

!

no ftp-server write-enable

!

!

!

!

interface Ethernet0/0

description ##internet##

ip address dhcp

ip access-group MY_WAN in

ip nat outside

half-duplex

!

interface FastEthernet0/0

description ## MY LAN##

ip address 192.168.1.1 255.255.255.0

ip nat inside

speed auto

!

interface Serial1/0

no ip address

shutdown

!

interface Serial1/1

no ip address

shutdown

!

ip nat inside source list MY_LAN interface Ethernet0/0 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

line aux 0

line vty 0 4

!

no scheduler allocate

!

end

[Richard Burts]

I do not see any obvious issues in the config and believe that this config should allow the router to connect to the cable modem. Would you post the output of show interface ethernet0/0

Can you also tell us about the connection between the router and the cable modem? What kind of cable is used? What is it connecting to on the cable modem.

I have seen some issues where it might be helpful to power cycle the devices. So you might do copy running startup on the router to save the config and then power cycle both the router and the cable modem.

It also occurs to me to wonder about the error messages that were interferring with the console output before and whether they might help us understand the issues on the router. So I would suggest that on the router you enter the configuration command logging buffer 32768. Then wait for a couple of minutes and then do show log. This will display the log messages without interferring with the console. Perhaps they might help us understand what is going on.

HTH

Rick

[breynold76]

I am using a cat6 cable between the router and the cable modem. it is connected to one of the four ethernet ports on the modem/gateway.

here is the log:

R1#show log

Syslog logging: enabled (0 messages dropped, 1 messages rate-limited,

                0 flushes, 0 overruns, xml disabled, filtering disabled)

    Console logging: disabled

    Monitor logging: level debugging, 0 messages logged, xml disabled,

                     filtering disabled

    Buffer logging: level debugging, 25 messages logged, xml disabled,

                    filtering disabled

    Logging Exception size (4096 bytes)

    Count and timestamp logging messages: disabled

    Trap logging: level informational, 226 message lines logged

Log Buffer (32768 bytes):

Mar  3 06:13:41.452: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:14:41.474: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:15:41.497: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:16:41.519: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:17:41.542: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:18:41.564: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:19:41.586: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:20:41.609: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:21:41.631: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:22:41.654: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:22:43.052: %SYS-5-CONFIG_I: Configured from console by console

Mar  3 06:23:41.676: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:24:41.698: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:25:41.721: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:26:41.743: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:27:41.766: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:28:41.788: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:29:41.810: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:30:41.833: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:31:41.855: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:32:41.878: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:33:41.900: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:34:41.930: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:35:41.953: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:36:41.975: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

Mar  3 06:37:41.998: %PQUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?

here is the show run:

R1#show int e0/0

Ethernet0/0 is up, line protocol is up

  Hardware is PQUICC Ethernet, address is 0004.dd0d.ba27 (bia 0004.dd0d.ba27)

  Description: ## internet ##

  Internet address will be negotiated using DHCP

  MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Half-duplex, 10BaseT

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input 00:00:00, output 00:00:02, output hang never

  Last clearing of "show interface" counters never

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 1000 bits/sec, 2 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     5949 packets input, 530517 bytes, 0 no buffer

     Received 5943 broadcasts, 0 runts, 0 giants, 0 throttles

     1065 input errors, 0 CRC, 0 frame, 0 overrun, 1065 ignored

     0 input packets with dribble condition detected

     1818 packets output, 298880 bytes, 0 underruns

     1065 output errors, 0 collisions, 1 interface resets

     0 babbles, 0 late collision, 0 deferred

     1065 lost carrier, 0 no carrier

     0 output buffer failures, 0 output buffers swapped out

[Richard Burts]

Thank you for posting the log messages. They definitely do indicate that there is a problem with connectivity between the cable modem and the router. I might suggest trying a different port on the cable modem and perhaps a different cable if you have it.

What is the model of the cable modem?

As an experiment I wonder what would happen if you were to connect the FastEthernet to the cable modem rather than the Ethernet interface.

HTH

Rick

[Bilal Nawaz]

Hello, this wont work. In your config you have this:

interface Ethernet0/0
description ##internet##
ip address dhcp
ip access-group MY_WAN in
ip nat outside
half-duplex

Please change it to this:

interface Ethernet0/0
description ##internet##
ip address dhcp
ip access-group MY_WAN in
ip nat outside
Speed 100
Duplex full

Having seen this, I strongly believe this may fix the problem. There is layer 2 problem in that your e0/0 interface is half duplex and needs to be set to full duplex.

Hope this helps!

Sent from Cisco Technical Support iPhone App

[Richard Burts]

That might be good advice for interface FastEthernet0/0 but it will not work on Ethenet0/0 which is a 10 Mb interface.

And even on a FastEthernet 100 Mb interface half duplex might slow things down but it would not stop it from working.

I am convinced that the problem here is something other than duplex setting.

HTH

Rick

[Bilal Nawaz]

Oh, yes of course - you're right Rick! its not a FastEthernet interface.

So we could try this instead?

interface Ethernet0/0

description ##internet##

ip address dhcp

ip access-group MY_WAN in

ip nat outside

duplex auto

speed auto

I've just tried this with a e0/1/0 interface connected to a linksys router:

interface Ethernet0/1/0

ip address dhcp

duplex auto

speed auto

Router#show int e0/1/0

Ethernet0/1/0 is up, line protocol is up (connected)

  Hardware is Lance, address is 0090.0c70.057b (bia 0090.0c70.057b)

  Internet address is 192.168.0.100/24

  MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  ARP type: ARPA, ARP Timeout 04:00:00,

  Last input 00:00:08, output 00:00:05, output hang never

  Last clearing of "show interface" counters never

  Input queue: 0/75/0 (size/max/drops); Total output drops: 0

  Queueing strategy: fifo

  Output queue :0/40 (size/max)

  5 minute input rate 1 bits/sec, 0 packets/sec

  5 minute output rate 4 bits/sec, 0 packets/sec

     2 packets input, 124 bytes, 0 no buffer

     Received 2 broadcasts, 0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     0 input packets with dribble condition detected

     3 packets output, 186 bytes, 0 underruns

     0 output errors, 0 collisions, 2 interface resets

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier

     0 output buffer failures, 0 output buffers swapped out

We'll just wait for the logs too as you said, this may help us out.

Hope this helps.

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

[breynold76]

R1(config-if)#duplex auto

                     ^

% Invalid input detected at '^' marker.

R1(config-if)#speed auto

               ^

% Invalid input detected at '^' marker.

[Bilal Nawaz]

Hello, I just had a thought. Instead of using the e0/0 interface, we could use the fa0/0 interface for both connections by doing something called router on a stick.

This means we would create sub interfaces on our router, and then we will need to create a vlan on the switch. One vlan will be used for Internet, and the other will be used for LAN.

The router configuration should look like this:

version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Router
!
no logging console
!
no aaa new-model
ip subnet-zero
!
!
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 8.8.4.4 8.8.8.8
!
no ftp-server write-enable
!
!
Interface e0/0
No IP address
Shutdown
!
Interface fa0/0
No IP address
Speed auto
Duplex auto
No shut
!
interface Fa0/0.100
Encapsulation dot1q 100
description ##internet##
ip address dhcp
ip access-group MY_WAN in
ip nat outside
!
interface FastEthernet0/0.1
Encapsulation dot1q 1 native
description ## MY LAN##
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface Serial1/0
no ip address
shutdown
!
interface Serial1/1
no ip address
shutdown
!
ip nat inside source list MY_LAN interface Fa0/0.100 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
line aux 0
line vty 0 4
!
no scheduler allocate
!
end

Now we've done the router config. We need to configure the switch. We will create a trunk link to carry both traffic for LAN and Internet from the different vlans to the router.

Like this

Vlan database
Vlan 1 name LAN
Vlan 100 name INTERNET
Exit
!
Conf t
!
Interface fa0/24
Description ## Trunk to Router ##
Switchport trunk encapsulation dot1q
Switchport mode trunk
Switchport trunk allowed vlan 1,100
!
Interface fa0/23
Description ## Link to Modem ##
Switchport mode access
Switchport access vlan 100

And this should be it! All your other ports on your switch (fa0/1 - 0/22) can be used as LAN ports

All you need to then do is plug from the router (fa0/0) to the switch (fa0/24)

Then plug the modem in to the switch (fa0/23)

And we're done.

Give this a go and let us know if we are seeing better results.

Hope this helps

Sent from Cisco Technical Support iPhone App

[breynold76]

this is what i get when i put in the speed 100 command

R1(config-if)#speed 100

               ^

% Invalid input detected at '^' marker.

[Bilal Nawaz]

Hello Bernard, could we please try reseating the cable?

From Cisco:

%PQUICC-1-LOSTCARR : Unit [dec], lost carrier. Transceiver problem?

Explanation    The Ethernet 10BASE-T cable is unplugged.

Recommended Action    Reconnect the 10BASE-T Ethernet cable.

I also changed to this and works for me...

interface Ethernet0/0

description ##internet##

ip address dhcp

ip access-group MY_WAN in

ip nat outside

duplex auto

speed auto

Hope this helps

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

[breynold76]

Like it was suggested to me i switched around the e0/0 and the fa0/0 so the internet was coming in on fa0/0 instead. I am a little under half way through the ccna course so i have not used command line in a switch yet but it looks like the switch is set to half duplex? please correct me if i am wrong. here is the message after erasing starup-config and starting over:

R1(config-if)#duplex auto

Mar  3 23:50:46.470: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethernet0/0 (not half duplex), with Switch FastEthernet0/9 (half duplex).

               ^

% Invalid input detected at '^' marker.

R1(config-if)#

Mar  3 23:51:00.096: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethernet0/0 (not half duplex), with Switch FastEthernet0/9 (half duplex).

Mar  3 23:51:46.472: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethernet0/0 (not half duplex), with Switch FastEthernet0/9 (half duplex).

[breynold76]

I got into the switch and changed all duplexes to full and speed to auto. that problem is fixed so now the router and switch are both on full duplex. it seems the router and the computer are both saying they are not receiving dhcp. I am guessing either the router is not configured properly or the cable modem/router is not sending out the dhcp.

[Bilal Nawaz]

Hello, you could try my suggestion of only using fa0/0 with sub interfaces in my previous post. This way you won't have to use the e0/0 since its only causing us problems at the moment.
With this method you use 100mb full duplex instead of the 10mb half duplex

Please try that and let me know how it goes.

Hope it helps

Sent from Cisco Technical Support iPhone App

[breynold76]

I did the router on a stick. it is getting a little closer. the magic jack phone that must have Internet is working. Pings to and from the computer and Cisco router are successful. There is now an ip address from the Cisco router instead of the cable modem. unfortunately there is still no Internet. when I do the diagnose on the computer it says the router has no Internet access.