Re: Cisco 3620 and Internet access - Page 2

raymondwrio · ‎02-08-2012

I have a Cisco 3620 router and I am trying to get internet access. My isp is comcast. All modem lights seem to be operational. But I do not have internet access. I can ping anything other then the router and I am on a home network.

I have attached a config file. Please note I am a novice with cisco routers.

cadet alain · ‎02-13-2012

Hi,

can you post your config and the output of:

-sh ip int br

-sh ip route

Regards.

Alain

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raymondwrio · ‎02-14-2012

Here is the requested info. And thanks for your time and patience.

sh ip int br

Interface IP-Address OK? Method Status Protocol

Ethernet0/0 192.168.3.1 YES NVRAM up up

Ethernet0/1 unassigned YES DHCP up up

Tunnel1 unassigned YES NVRAM up down

sh ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is not set

C 192.168.3.0/24 is directly connected, Ethernet0/0

cadet alain · ‎02-14-2012

Hi,

you didn't receive a dhcp address from the ISP on eth0/1 and you didn't configure a defaulr route as explaine in the Cisco doc I posted before.

enable debug for dhcp in privileged mode: debug dhcp detail

renew the IP with the privileged command renew dhcp

Post the output of the log.

Regards.

Alain

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ebarticel · ‎02-14-2012

Hi

You mention comcast, is that satellite connection?

Eugen

raymondwrio · ‎02-14-2012

eugen,

No it's cable with a cable modem. Ray

raymondwrio · ‎02-14-2012

Alain,

Ok I added in the ip route as:

ip route 0.0.0.0 0.0.0.0 192.168.100.1

This is my comcast default gateway address. It does work as I can log into it.

I attached the debug file and the renew dhcp command did not work. Did you mean the dos ipconfig /release command?

Ray

ebarticel · ‎02-14-2012

Hi Ray,

I found this posts, it may help you with your problem

http://forums.techarena.in/networking-security/1181169.htm

Eugen

raymondwrio · ‎02-15-2012

Eugen,

Tried that and no difference. The Ipconfig command relates more to the local pc then to the cable modem ip. I also tried to reset the ip to the cable modem using the reset button on the rear of the it but I still windup the same ip address.

Thanks Ray.

cadet alain · ‎02-15-2012

Hi,

Can you try this:

-connect PC directly to modem

-ipconfig/all to see default-gateway

-plug the pc to router and do a ipconfig/release and ipconfig/renew

-change the mac address of the router interface you're going to connect to cable modem to the mac of the pc with interface command: mac-address xxxx.xxxx.xxxx

-connect router to cable modem with the interface command ip address dhcp

-renew the lease with dhcp renew ethernet x/x in privileged mode

-add a default route pointing to next-hop found in the first ipconfig/all: ip route 0.0.0.0 0.0.0.0 x.x.x.x

let us know and post the output of ipconfig/all when connected to modem then when connected to router

as well as:

sh ip int br | exc una

sh int ethernet x/x | i bia

sh ip route static

then also provide results from a ping on router to:

-the next-hop in the static route

-if before succeeds then to 8.8.8.8

-if success then to 8.8.8.8 sourcing from LAN: ping 8.8.8.8 so x.x.x.x

Let us know.

Regards.

Alain

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raymondwrio · ‎02-15-2012

Alain,

-connect PC directly to modem(done)

-ipconfig/all to see default-gateway(done DW=192.168.100.1, note this has always been the DW)

-plug the pc to router and do a ipconfig/release and ipconfig/renew(done)

-change the mac address of the router interface you're going to connect to cable modem to the mac of the pc with interface command: mac-address xxxx.xxxx.xxxx (do you mean the pc mac? if yes then done)

-connect router to cable modem with the interface command ip address dhcp (e0/1 is connected the the cable modem, so run the ip address dhcp from there?)

-renew the lease with dhcp renew ethernet x/x in privileged mode(this command does not work where stated)

-add a default route pointing to next-hop found in the first ipconfig/all: ip route 0.0.0.0 0.0.0.0 x.x.x.x(x.x.x.x is set to the DW mentioned above)

Thanks Ray

cadet alain · ‎02-15-2012

Hi Ray,

Raymond Rio a écrit:

Alain,

-connect PC directly to modem(done)

-ipconfig/all to see default-gateway(done DW=192.168.100.1, note this has always been the DW)

-plug the pc to router and do a ipconfig/release and ipconfig/renew(done)

-change the mac address of the router interface you're going to connect to cable modem to the mac of the pc with interface command: mac-address xxxx.xxxx.xxxx (do you mean the pc mac? if yes then done)

Yes

-connect router to cable modem with the interface command ip address dhcp (e0/1 is connected the the cable modem, so run the ip address dhcp from there?)

Yes

-renew the lease with dhcp renew ethernet x/x in privileged mode(this command does not work where stated)

enable

# dhcp renew e0/1

-add a default route pointing to next-hop found in the first ipconfig/all: ip route 0.0.0.0 0.0.0.0 x.x.x.x(x.x.x.x is set to the DW mentioned above)

Thanks Ray

But you didn't post the outputs and were you able to ping 8.8.8.8 from PC when connected with PC to modem?

What is the exact model of modem?

Post the outputs I asked above please.

If it worked with PC can you clear arp cache of PC with arp -d * then ping 8.8.8.8 while sniffing the interface with wireshark and upload the capture file

Regards.

Alain

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raymondwrio · ‎02-15-2012

Ok when I'm connect pc to cable modem I can ping 8.8.8.8 successfully. But when connected to router it does not ping, or for matter anyother ip address. I have made no other changes to the config file other then the mac address change.

Modem is RCA digital broadband , model dcm425.

Outputs

ccefl#sh ip int br

Interface IP-Address OK? Method Status Protocol

Ethernet0/0 192.168.3.1 YES NVRAM up up

Ethernet0/1 unassigned YES DHCP up up

Tunnel1 unassigned YES NVRAM up down

ccefl#

ccefl#sh int ethernet 0/1

Ethernet0/1 is up, line protocol is up

Hardware is AmdP2, address is 000b.46cc.8fc2 (bia 000b.46cc.8fc2)

Description: exit

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)

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

Last input 00:00:00, output 00:00:03, 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 19000 bits/sec, 37 packets/sec

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

11808 packets input, 735758 bytes, 0 no buffer

Received 11808 broadcasts, 0 runts, 0 giants, 0 throttles

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

0 input packets with dribble condition detected

111 packets output, 21726 bytes, 0 underruns

50 output errors, 0 collisions, 1 interface resets

0 babbles, 0 late collision, 0 deferred

50 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

ccefl#

ccefl#sh ip route static

ccefl# (note it returns just a blank line)

cefl#ping 192.168.100.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.100.1, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

ccefl#ping 8.8.8.8

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

cadet alain · ‎02-15-2012

Hi,

1)

ccefl#sh int ethernet 0/1

Ethernet0/1 is up, line protocol is up

Hardware is AmdP2, address is 000b.46cc.8fc2 (bia 000b.46cc.8fc2)

You didn't change the MAC address because otherwise it would be different from the Burned-In address(bia)

2)

Ethernet0/1 unassigned YES DHCP up up

You have no IP on the interface so the following is normal:

cefl#ping 192.168.100.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.100.1, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

3)

ccefl#sh ip route static

ccefl# (note it returns just a blank line)

You have no default route because you have no ip address on the interface

Regards.

Alain

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ebarticel · ‎02-15-2012

Hi,

The modem "knows" when you connect a PC or a router to it. That's why you cannot get an ip from it, because it recognize it by mac address.

First you need to connect PC to router and give ip on same subnet, then check your arp cache and write down the PC mac address, then use the commands Alain have suggested to change your mac on the interface that will connect to modem.

Eugen

raymondwrio · ‎02-16-2012

Gents,

I have attached the wireshark output file, a screen shot of the arp -a file and a recent config file.

Still fails to connect to internet.

interface Ethernet0/0

mac-address 000b.46cc.8fc1 (This is the mac addr of the E0/0 interface card)

ip address 192.168.3.1 255.255.255.0

ip nat inside

no ip route-cache

no ip mroute-cache

full-duplex

no cdp enable

!

interface Ethernet0/1

description exit

mac-address 0006.5b77.89b5 (This is the mac addr of the of my PC.)

ip address 192.168.100.1 255.255.255.0

ip nat outside

no ip route-cache

no ip mroute-cache

full-duplex

no cdp enable

List of mac addr:

000b.46cc.8fc1 = E0/0

000b.46cc.8fc2 = E0/1

0006.5b77.89b5 = PC

0011.e398.dcc6 = modem