[CLUE-Tech] Cisco 678 Configuration

[black at galaxy.silvren.com]

That's pretty wild. Under the ARP section it complains about two invalid
MAC addresses answering for 192.168.1.1, one after another and they are
exactly 1 digit apart. That isn't a multicast MAC address, so it has
absolutely no reason to be there. They also don't match the MAC address of
the ethernet port on your Cisco 678.

I'd guess that's the key to the whole situation. Any time a host on your
home network tries to get to something out on the 'net it will have to
send to your 678, and if someone else is answering ARP requests for that
address, you'll have problems. Sorry if that came across as networking
101, I'd guess you already know that but I threw it in for completeness.
:)

Are you sure there isn't something on your LAN assigned to that address?
Doesn't seem likely since you said you connected directly to the 678 and
it still didn't work.

Have you tried doing a traceroute from somewhere out on the Internet (dial
in, perhaps) to your 678? I know you said Qwest can get to it, but if
there's some bizarre routing problem between Qwest and where you're dialed
in they'll not see it. This still won't explain the ARP weirdness,
however.

You could also unplug the 678 from the network, try to ping 192.168.1.1
and fire up ethereal to see if anything else is trying to answer for that
address or sending back ARP replies.

If worse comes to worse you can just blow the configuration off the 678
and start over. Maybe something is "stuck" in the config. This will be a
lot easier than trying to put a new CBOS image.

On Wed, 3 Dec 2003, Randy Arabie wrote:

> Hello fellow Linux enthusiasts.  I've been racking my brain over a Cisco 678
> DSL router configuration problelm for several days now.  This particular router
> worked fine on the Qwest network in Denver for 2+ years.
>
> I thought setting it up here in Bellingham, WA would be a breeze.  I've got DSL
> with Qwest here, also. The network is DMT, just as it was in Denver.
>
> The router doesn't seem to be routing, sort of.  When I connect it to the phone
> line it trains and the wan0 port(s) link up with the upstream network.
> The "inside" eth0 is configured to the standard class C 192.168.1.1 with the
> internal DHCP server configured to dish out IP's.  And, NAT is enabled.  I've
> also enabled the telnet server so my ISP's techies could try and help me figure
> out why it won't work.
>
> Using the serial management interface, from the cbos prompt I can ping and
> traceroute to public IP's out on the net.  And, the support folks at my ISP can
> telnet into the router from the outside.  IMO, this cofirms that there are no
> problems with the wan0 interface.
>
> LAN hosts connected either directly to the router, or via a hub get assigned
> IP's with the appropriate gateway and DNS servers.  These hosts can ping the
> router's eth0 interface (192.168.1.1) and each other.  However, they cannot
> telnet to the router's eth0 interface.  And AFAICT, they can't ping anything
> past the router's eth0 interface.  Maybe the ping requests are getting out, but
> the replies aren't getting back.
>
> Using the serial management interface, from the cbos prompt I cannot ping any
> of my LAN hosts.  I've run ethreal on my laptop and confirmed that no ping
> requests are comming from the router.  And, I've also captured the results of
> pinging the router from my laptop, along with other expriments.
>
> Here's a link to the ethreal output file [tcpdump format]:
>
>   http://www.arabie.org/pub/ethreal.out
>
> The only questionable thing I've seen on the router is the arp table.  On a
> number of occaisions I've seen entries labeled as "invalid" and the MAC address
> for the entry doesn't match either my laptop or the router.  I've cleared the
> router's arp table, rebooted it, and tried again but the thing still won't
> work.  These entries appear when I try to telnet to hosts outside my LAN.  Or,
> when I try to telnet to the public IP assigned to the router's wan0-0 interface.
>
> Here's a link to a transcript of my cbos session:
>
>   http://www.arabie.org/pub/cisco678.txt
>
> If you scan down to my "show nat" and "show arp" commands, those correspond to
> times when I've tried to telnet out from an internal host.
>
> I'm dropping the router off with my ISP, and I think they are gonna have a
> loaner for me.  Their techie is going to have a look at it.  So far, they don't
> know what the problem is.
>
> I'm stumped.  It has to be some sort of config problem.  I'm ready to flash the
> thing with a new cbos image.  It's running v2.4.3, and I think the current it
> 2.4.6.  However, I'm not sure how to do that. Since I can't even connect via
> telnet, I doubt tftp would work.  How would I get the image onto it?
>
> Maybe one of you networking guru's will have an idea...
>
> --
> Allons Rouler!
>
> Randy
> http://www.arabie.org/
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