02-08-2012 06:46 AM - edited 03-07-2019 04:48 AM
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.
02-13-2012 02:40 PM
Hi,
can you post your config and the output of:
-sh ip int br
-sh ip route
Regards.
Alain
02-14-2012 05:14 AM
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
02-14-2012 05:33 AM
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
02-14-2012 06:30 AM
Hi
You mention comcast, is that satellite connection?
Eugen
02-14-2012 08:57 AM
eugen,
No it's cable with a cable modem. Ray
02-14-2012 11:59 AM
02-14-2012 05:35 PM
Hi Ray,
I found this posts, it may help you with your problem
http://forums.techarena.in/networking-security/1181169.htm
Eugen
02-15-2012 07:13 AM
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.
02-15-2012 07:38 AM
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
02-15-2012 09:17 AM
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
02-15-2012 11:33 AM
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
02-15-2012 01:07 PM
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)
02-15-2012 02:10 PM
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
02-15-2012 04:50 PM
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
02-16-2012 06:25 AM
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
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