Re: strange problem connecting 2 linux boxes

From: Alex Harsch (infodude_at_gmx.de)
Date: 05/14/04


Date: Fri, 14 May 2004 15:52:24 +0200

Sting wrote:

> Hello,
> - Last week I had posted here a
> strange problem I had connecting 2 linux boxes.
> I had done some more tests and I am quite in despair.
> please help!
>
> - I had tried to conenct 2 Linux boxes directly.
> I did it with a cross cable connecting directly
> one nic to the other nic.
> (also tried all my tests with non-cross cable,
> but AFAIK it should be with cross cable).
>
> Clifford Kite asked about that cable: it is a brand new cable
> that I bought, and testd today on other machines, and
> it's OK.
>
> For this I set the address of one of them to
> 192.168.0.2
> subnet: 255.255.255.0
>
> the other is
> 192.168.0.1
> subnet: 255.255.255.0
>
>
> Now I can't ping from 192.168.0.2
> to 192.168.0.1.
>
> I tried to remove the GW declaration from
> 192.168.0.2 (the gw was 192.168.0.254 , and
> in this connection both of them were not conneced to
> 192.168.0.254).
> I also tried, on 192.168.0.2 ,to set the gw to itself,
> namely 192.168.0.2 but it did not help.
>
> what adds to this strangeness is , that when
> I took the 192.168.0.1 and connected it to a different
> machine with the same non-corss cable - I could ping it!!
>
>
> Now , I had done another test:
> connecting them through a hub, with 2 non cross
> cables. And again - no ping.
>
> I know for sure that these cables are OK,
> because immedaitely afterwards
> I connected them to a cable modem and they were OK
> (I am currently posting this message using one of them ...
> were it not OK you could not read this post...).
>
> Clifford asked about some data:
> the output of route from 192.168.0.2:
>
> routing table at work
> Kernel IP routing table
>
> Destination Gateway Genmask Flags Metric Ref Use
> Iface
> 192.168.0.0 * 255.255.255.0 U 0 0 0
> eth0
> 169.254.0.0 * 255.255.0.0 U 0 0 0
> eth0
> 127.0.0.0 * 255.0.0.0 U 0 0 0 lo
> default 192.168.0.254 0.0.0.0 UG 0 0 0
> eth0
>
>
>
>
>
> ifconfig of 192.168.0.2 gives:
> ifconfig
> eth0 Link encap:Ethernet HWaddr 00:0D:61:10:B8:AC
> inet addr:192.168.0.2 Bcast:192.168.0.255 Mask:255.255.255.0
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:3109 errors:0 dropped:0 overruns:0 frame:0
> TX packets:2820 errors:0 dropped:0 overruns:0 carrier:0
> collisions:661 txqueuelen:100
> RX bytes:912643 (891.2 Kb) TX bytes:2277008 (2.1 Mb)
> Interrupt:11 Base address:0x9000
>
> lo Link encap:Local Loopback
> inet addr:127.0.0.1 Mask:255.0.0.0
> ......
>
> what can it be ?
> please help !
>
> regards,
> sting
Hi,

first of all, routes and gateways don't play a role in this case.
Can both machines ping themselfs? Can both machines ping 127.0.0.1.
Is the firewall acrivated (post iptables-save)? Use the cable you use to
connect your modem. This is a cross link, and you can plug it in directly
in both machines, without a hub.

Alex