Cisco 2620 to Comcast trouble.

Im a bit troubled by the debug output. My understanding of DSL modems is that you configure them with the username and password (from memory) and they automatically connect to the ISP, so you do not need to enter any authentication information on your router, like the Cisco document Neon pointed to.

Since speedy writes that he connected the DSL modem to his switch and stuck on a few computers with DHCP enabled and this worked, it is obvious no authentication is required. It's all handled by the DSL modem.

Now, coming to the encapsulation error, this is surely the reason, or at least ONE of the reasons your unable to connect with the router and we are going to solve it... it just might require a few posts more

One thing I noticed on the document Neon pointed us to was the mtu which was configured to 1492, which could be a possible reason.... however, since you mentioned the error generated was from a 'ping' and the error clearly shows a packet length of 100 bytes, the MTU is surely not the problem here. (doh!)

So what next?

Connect the router to the DSL modem and do NOT connect anything to your router's LAN

All right... I did exactly what you said. Oh. I feel obligated to point out that I don't have a DSL modem. It's actually an RCA cable modem. I wish it was DSL, if it was, I could pick up a WIC-1adsl, and skip the Ethernet interface. But I can't. Sometimes one must work with what they're given, right?

So, on that note, heres the (somewhat substanial) output from debug all :


%Error opening tftp://255.255.255.255/cisconet.cfg (Timed out)debug all

This may severely impact network performance. Continue? (yes/[no]): yes
All possible debugging has been turned on
2600#
00:03:34: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:34: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.144 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:35: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:35: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.82 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:35: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:35: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.3.253 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:35: MobileIP: Ethernet1/0 add 24.118.152.1 rejected
00:03:35: IP ARP req filtered src 24.118.152.1 000b.bf53.5054, dst 24.118.154.205 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:35: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:35: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.62 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:35: MobileIP: Ethernet1/0 add 24.118.152.1 rejected
00:03:35: IP ARP req filtered src 24.118.152.1 000b.bf53.5054, dst 24.118.154.49 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:36: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:36: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.154.175 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:36: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:36: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.96 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:36: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:36: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.152.242 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:36: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:36: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.89 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:36: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:36: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.1.194 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:37: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:37: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.152.209
2600# 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:37: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:37: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.71 0000.0000.0000 wrong cable, interface Ethernet1/0%Unknown DHCP problem.. No allocation possible
00:03:37: DHCP: Waiting for 30 seconds on interface Ethernet1/0
00:03:37: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:37: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.1.30 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:37: MobileIP: Ethernet1/0 add 24.118.152.1 rejected
00:03:37: IP ARP req filtered src 24.118.152.1 000b.bf53.5054, dst 24.118.154.132 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:37: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:37: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.15pin5.129 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:37: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:37: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.1.204 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:37: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:37: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.144 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:38: MobileIP: Ethernet1/0 add 24.118.152.1 rejected
00:03:38: IP ARP req filtered src 24.118.152.1 000b.bf53.5054, dst 24.118.155.19 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:38: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:38: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.44 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:38: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:38: IPg 1 ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.3.253 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:38: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:38: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.62 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:38: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:38: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.96 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:39: IP: NAT enab = 1 trans = 0 flags = 82
00:03:39: IP: s=10.228.32.1 (Ethernet1/0), d=255.255.255.255, len 373, rcvd 2
00:03:39: UDP: rcvd src=10.228.32.1(67), dst=255.255.255.255(68), length=353
00:03:39: IP: s=10.228.32.1 (Ethernet1/0), d=255.255.255.255, len 373, dispose udp.noport
00:03:39: DHCP: Received a BOOTREP pkt Not for us..: xid: 0x9411C1B0
00:03:39: MobileIP:46. Ethernet1/0 add 24.245.0.1 rejected
00:03:39: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.3.78 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:39: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:39: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.216 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:39:
00:03:39: Rudpv1 Sent: Pkts 0, Data Bytes 0, Data Pkts 0
00:03:39: Rudpv1 Rcvd: Pkts 0, Data Bytes 0, Data Pkts 0
00:03:39: Rudpv1 Discarded: 0, Retransmitted 0
00:03:39:
00:03:39: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:39: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.89 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:40: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:40: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.154.125 0000.0000151.0000 wrong cable, interface Ethernet1/0
00:03:40: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:40: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.1.30 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:40: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:40: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.144 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:40: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:40: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.1.243 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:41: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:41: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.2.105 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:41: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:41: IP ARP req filtered s.27rc 66.41.152.1 000b.bf53.5054, dst 66.41.152.209 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:41: TFTP: Sending read request
00:03:41: UDP: sent src=192.168.0.1(55743), dst=255.255.255.255(69), length=27
00:03:41: IP: s=192.168.0.1 (local), d=255.255.255.255 (FastEthernet0/0), len 47, sending broad/multicast
00:03:41: IP: s=192.168.0.1 (local), d=255.255.255.255 (Ethernet1/0), len 47, sending broad/multicast
00:03:41: NAT: translation failed (G), dropping packet s=192.168.0.1 d=255.255.255.255
00:03:41: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:41: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.2.192 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:41: MobileIP: Ethernet1/0 add 24.118.152.1 rejected
00:03:41: IP ARP req filtered src 24.118.152.1 000b.bf53.5054, dst 24.118.154.49 0000.0000.0000 wrong cable, interf.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 146.151.27.1, timeout is 2 seconds:
ace Ethernet1/0
00:03:41: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:41: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.86 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:42: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:42: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.71 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:42: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:42: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.96 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:42: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:42: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.216 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:42: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:42: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.144 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:42: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:42: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.1.194 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:43: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:43: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.2.27 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:43: MobileIP: Ethernet1/0 add 24.118.152.1 rejected
00:03:43: IP ARP req filtered src 24.118.152.1 000b.bf53.5054, dst 24.118.154.132 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:43: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:43: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.1.6 0000.000.0.0000 wrong cable, interface Ethernet1/0
00:03:43: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:43: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.2.105 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:43: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:43: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.1.243 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:43: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:43: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.2.192 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:44: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:44: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.168 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:44: IP: s=192.168.0.1 (local), d=146.151.27.1, len 100, unroutable
00:03:44: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:44: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.82 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:44: MobileIP: Ethernet1/0 add 24.245.0.1 rejected
00:03:44: IP ARP req filtered src 24.245.0.1 000b.bf53.5054, dst 24.245.0.96 0000.0000.0000 wrong cable, interface Ethernet1/0
00:03:44: MobileIP: Ethernet1/0 add 66.41.152.1 rejected
00:03:44: IP ARP req filtered src 66.41.152.1 000b.bf53.5054, dst 66.41.155.62 00


Hope that helps. Thanks!

Chris Stoopes

Ethernet1/0%Unknown DHCP problem.. No allocation possible

00:03:37: DHCP: Waiting for 30 seconds on interface Ethernet1/0

00:03:39: DHCP: Received a BOOTREP pkt Not for us..: xid: 0x9411C1B0

I'm going to state the obvious here -- it looks like the DHCP is broken.. is an IP address being properly assigned on eth 1/0 ?

After going through that looooooong debug output I have come to the conclusion that your problem is definately got to do with routing and dhcp.

Before I say anything else, I need you to try a few more commands and post back the results so we can conclude:

Switch the router on as normal and from the console, try to ping a external host. When this process finishes, enter the following commands :

1) Show arp

You will see a few entries, post them all here. I'm interested in at least one with a "incomplete" entry.

2) show ip interface [ethernet 0/1 & fast ethernet 0/1]

We want to take a look at the ip addresses assgined to both ethernet interfaces. Sahir correctly noted that there might be a problem with the Ethernet interface connected to the RCA modem, not obtaining an IP address and the debug shows errors related to this.

3) debug arp

Once you enter this command, try and ping a different Internet host from the console and paste the results here.

Once finished, 'undebug all'

4) debug dhcp detail

Paste the results here, and 'undebug all'

5) sh ip route

Paste the results here.

As a note, when you post each sections results, use the "code" tags provided above to place the result for each command in a nice black table, making it much easier for us to read.

Hopefully the above information should be the last required to solve your problem.

Cheers,

All right. Sorry this has taken so long. I was out of town Friday - Saturday. When I got back Saturday night, I played with it a little, going on the knowledge that maybe it was the DHCP. I noticed it wasn't giving me the message, "interface x/x assigned address x.x.x.x by DHCP". As Sahirh stated, that must have been why it was giving DHCP errors. I know that it used to request an address. I couldn't get the 2600 to request an address, so I switched the interfaces. That did work. The cable modem assigned me an address quick as a button. But it wouldn't give me a ping to anything. It was getting late, and the thing was *really* starting to frustrate me, so I went to bed.

So today I took your advice from before, and decided that the best thing to do would be to with the simplest configuration, and begin to add things from there. I tried with a much more base config, listed here, (1 interface shutdown, no routing, no dhcp server, FastEthernet interface on DHCP)

2600#show config
Using 732 out of 29688 bytes
!
version 12.2
service config
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname 2600
!
enable secret 5 XXXXXXXXXXXXXXXXXXXXXXXXX.
enable password XXXXXXXXXX
!
clock timezone central -6
ip subnet-zero
!
!
ip dhcp ping packets 1
!
ip audit notify log
ip audit po max-events 100
!
no call rsvp-sync
!
interface FastEthernet0/0
ip address dhcp
no ip mroute-cache
duplex auto
speed auto
no cdp enable
no mop enabled
!
interface Ethernet1/0
no ip address
shutdown
full-duplex
no cdp enable
no mop enabled
!
ip classless
no ip http server
!
!
!
dial-peer cor custom
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
password XXXXXXX
login
!
end

2600#ping yahoo.com

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 66.218.71.113, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/68/72 ms
2600#

That config worked great. It got a DHCP address quick as can be, and pinged out just fine. Success! So... I tried the same thing with the interfaces switched. Same type of config, but Ethernet 1/0 instead of FastEthernet 0/0. Config listed below:

show config
Using 734 out of 29688 bytes
!
version 12.2
service config
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname 2600
!
enable secret 5 XXXXXXXXXXXXXXXXXXXXXX
enable password XXXXXXX
!
clock timezone central -6
ip subnet-zero
!
!
ip dhcp ping packets 1
!
ip audit notify log
ip audit po max-events 100
!
no call rsvp-sync
!
interface FastEthernet0/0
ip address dhcp
no ip mroute-cache
shutdown
duplex auto
speed auto
no cdp enable
no mop enabled
!
interface Ethernet1/0
ip address dhcp
full-duplex
no cdp enable
no mop enabled
!
ip classless
no ip http server
!
!
!
dial-peer cor custom
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
password XXXXXXX
login
!
end

2600#ping yahoo.com

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 66.218.71.114, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/68/72 ms
2600#

This also netted a success.

So... I'm not sure where to go from here. I know both of the interfaces work, which I was starting to worry about. You must be right, the problem is probably somewhere in the routing, and was definitly in the DHCP client, which wasn't getting an address.

Could it be some sort of conflict with the DHCP server running on the 2600? I kind of wondered how you can have the router be a DHCP client and then run a server with no description of which interface to run the server on. Maybe thats part of the problem? I'll try adding a couple of things, and see what happens, how does that sound?

I don't want you to feel like I was ignoring your posts Chris. I don't believe that your directions were there last night when I read Sahirh's post and so I proceeded from there with what he noticed. Your advice, especially your beginning advice actually, was very helpful.

Thanks!

Chris

This is odd. The good news is that it seems to work fine, but I'm not sure why. I added some of the config lines:

interface FastEthernet 0/0
ip nat inside

interface Ethernet 1/0
ip nat outside

If you look at the old config, I believe that I had typed this:
ip nat inside source list 1 interface FastEthernet0/0 overload

As soon as I added the above line, it stopped pinging the 'net.

So I changed it to:
ip nat inside source list 1 interface Ethernet1/0 overload

Also added:
access-list 1 permit any


Tried pinging, and it worked! So the NAT was assigned to the wrong interface I believe. Oddly enough, as soon as I added the routing line, it stopped working.

I added this: route ip 0.0.0.0 0.0.0.0 Ethernet 1/0

And it simply wouldn't go. So I removed it, and it would ping just fine. Odd. I went to the network config on my computer, gave it a 192.168.0.0 address, set the gateway as the 2620, and here I am at your website. Not quite sure how that works. Any ideas?

Thanks for your help.

Chris