strange ping problem ( lan / router / wan )

[CapNemo]

hi all :)

i just downloaded knoppix 3.7, and booted from cd (nothing installed on hdd, yet)
now i'm trying to connect the linux box to my lan and thru my router to the wan.

- the router ( from SMC ) has a default ip address of 192.168.2.1
- the linux box uses a wired connection ( normal cat5 cables, with a switch in between the router and the box )
- dhcp is disabled, all clients use fixed ip addresses
- i used "knoppix nodhcp 2" at the knoppix boot prompt

if i assign an ip to eth0 and set default gateway, broadcast and nameserver, the following happens:
- the linux box is able to ping itself
- the linux box is able to ping other boxes in the lan
- other boxes are able to ping the linux box
- other boxes are able to ping the router
- the linux box CAN NOT ping the router
- the linux box CAN NOT connect to the wan
- if the linux box pings broadcast ( 192.168.2.255 ) only the linux box responds
- (not sure on that, but i guess the linux box has an MTU of 1500; the router of 1492, does that matter in any way, if yes, how do i change it? )

what do i need to do to be able to ping the router, and connect to the wan?

tried to use the search function, but found nothing yet...

thanks in advance :)

Nemo

[Harry Kuhman]

You might want to tell us all of the settings that you made with netcardconfig.

I understand that you have static IP addresses on all of the other systems (and I understand why, even though this is a pain, that you would want to do this with an SMC router). However, even if all other devices have static IP settings, the router can still run DHCP (just make sure that the range of addresses that it hands out does not contain any of the static addresses. Let it hand out 220 to 230 for example). If you do that can Knoppix connect to it, configure with DHCP and talk normally? (Yes, you may still want to give it a static setting, but this test should tell us a lot and looking at the configuration might show what is configured differently.)

It sure doesn't make any sense that you could ping other boxes on the local network but not the SMC router. Can you ping other computers plugged into different router ports, or can you only ping computers that share the switch before the router? Have you tried plugging the Knoppix box right into a router port to take the switch out of the picture (not that I can imagine anything the switch could be doing wrong in this case)?

[CapNemo]

hey's ;)

you're fast, wow :)

my settings are:
- router:
-- ip: 192.168.2.1
-- dhcp off
-- acts as default gateway and nameserver

- linux box:
-- ip: 192.168.2.x (tried several)
-- dhcp should be off, at least it said so at boot time ;)
-- set default gateway to 192.168.2.1
-- set broadcast to 192.168.2.255
-- set nameserver to 192.168.2.1

- other boxes:
-- ip: 192.168.2.y (other ip addresses, of course ;)
-- dhcp off
-- etc...

if i do network-setup it tries to enter all values, sets some routes and still remains "offline"...

any ideas?

thank you,
Nemo

EDIT:
it's not a 3com nic, btw ;)

[Harry Kuhman]

.....any ideas?

Nope, same questions as before. What happend if you turn on DHCP in the router (this will cause no problems for the other systems that configure themselves statically, you can mix both on a system as long as you do not try to hand out the static address range) and then boot knoppix without the cheat code that turns off DHCP? Have you tried going right into a router port and bypassing the switch? You can post the actual 192.168.2.x addresses, there is no security issue in us seeing them. No, under normal conditions it shouldn't make a difference, but just maybe something can be spotted from the real data rather than the condedsed sanatised data (I caught at least one other problem that way some time ago in these forums, user knew better but was making a subconscious mistake that he just couldn't see until it was pointed out to him).

Beyond this you might want to try running ethereal and sniffing your packets to see just what is going out on the wire and if anything looks dufferent about a ping to the router than to another local computer.

[CapNemo]

i tried what you suggested and enabled dhcp on the router.
knoppix couldn't assign an ip address while booting, and network-setup couldn't either later on.
if i enter the values manually again, i get the same results.

i can ping different boxes, wired and wireless, not only those connected to the same switch.

/me scratches head ;)

Nemo

EDIT:
you're really fast *g* :)
i cannot connect it directly to the router (it's a cable mess already, and i cannot move the router or the box atm.. but all other machines using that switch (4 port) are working normally...
tried to use tcpdump, only message i see while trying to ping is "arp who-has 192.168.2.1 tell 192.168.2.x", does it need to know the routers mac address too?
i'm going to try ethereal now...

[Harry Kuhman]

i tried what you suggested and enabled dhcp on the router.
knoppix couldn't assign an ip address while booting, and network-setup couldn't either later on.
if i enter the values manually again, i get the same results.Nemo

By network-setup I hope you mean netcardconfig, but I wanted to ask. I think were's going to have to be very exact on or terms and keywords if we are going to track this down and not make assumptions about what the other is saying.

With the router's DHCP enabled and Knoppix booted without the nodhcp cheat code, try the two following commands from a shell "sudo mii-tool -r" and "netcardconfig". When Netcardconfig starts, take the YES option. Please post back the exact text of any errors.

I'm still hoping that ethereal might be giving you some insight, as I do have doubts that the above will tell us that much. Certainly your card is working fine if it can ping other local systems. It might help to post back the exact text of the result of the ifconfig command. You could also use ifconfig to change your mtu if you really think that could be an issue, but I don't see how it could be for a simple ping. And you might want to look at the man page for ifconfig for other inspiration.

[CapNemo]

...
You can post the actual 192.168.2.x addresses, there is no security issue in us seeing them.
...

*lol*
i used .x because i tried several different addresses with the same result.
i assigned my normal boxes adresses in the range of .10 to .99 and tried these at the linux box:
.19 <- not used on other boxes
.111 <- far away from the other range, just to be sure
.200 - .230 <- the router should hand out these with dhcp, the linux box couldn't get one, for whatever reason...
.210 <- assigned manually, while the router was dhcp enabled

thanks for your patience :)
Nemo

[Harry Kuhman]

EDIT:
you're really fast *g*
i cannot connect it directly to the router (it's a cable mess already, and i cannot move the router or the box atm.. but all other machines using that switch (4 port) are working normally...
tried to use tcpdump, only message i see while trying to ping is "arp who-has 192.168.2.1 tell 192.168.2.x", does it need to know the routers mac address too?
i'm going to try ethereal now...

Please quit editing to add information, as I don't get any notification that there is more information posted that way. Just add a new post to the thread.

Also, please stop the 192.168.2.x stuff. This is where it really matters and I can't tell what is hapening when you make the changes to Xs. All 192.168 addresses are completely local and cannot be reached across the network, so there is no security issue here and no reason to hide local addresses.

ARP (address resolution protocol) is one of the things that you see when you sniff the wire. It seems that ARP is working if other pings are getting to you and back to you across the network, but since we have a situation that makes no sense here I don't want to just assume that. You should see different ARP packets. You will not see other systems respond to the router since you are on a switch rather than a hub (although you could see these packets with ethereal on the other system, there is a windows version as well as a linux version).

What will happen during ARP is an exchange of IP and MAC address information. This is how the system matches up IP to MAC addresses.

For that matter, have you tried to boot the Knoppix CD on any of the other systems? Is this problem local to this one PC, or does it exist when any PC tries to ping the router from Knoppix?

[Harry Kuhman]

The last post about 192.168.2.x was written before I saw you response. Thanks, but lets just try to use real addresses, just in case something shows up somewhere when we do.

[CapNemo]

sorry, was used from other boards to use edit, wont do any more.

the router is dhcp enabled now, and should hand out addresses in the range of .200 to .230
restarted knoppix without any "cheatcodes", dhcp enabled.

did the commands like you stated it, no error messages on "sudo mii-tool -r"
if i run netcardconfig i get the following errors:
--- snip ---
Sende DHCP Broadcast von Netzwerkkarte eth0eth0: link up
Operation failed.
Fehlgeschlagen.
Eingabetaste zum beenden.
--- snip ---

translated to somewhat like:
--- snip ---
Sending DHCP Broadcast from nic etc0etc0: link uo
Operation failed.
Failed.
Enter to finish.
--- snip ---

cannot try on other machines atm, they're in use or wireless, going to try later on.

again, thanks a bunch :)
Nemo