[SATLUG] Having connection issues with a crossover cable

John Pappas j at jvpappas.net
Tue Jul 21 22:51:11 CDT 2009


On Tue, Jul 21, 2009 at 00:59, Christopher Lemire <
christopher.lemire at gmail.com> wrote:

> i need help with a crossover connection. i've setup static ip
> addresses on both ends, /proc/sys/net/ipv4/ip_forward = 1, both in the
> same netmask, lights on ethernet cards both show connectivity,
> iptables has no rules enabled. What could be the issue here?


Is this an actual ethernet crossover cable (Rusty on the colors so LMGTFY)?
An incorrectly wired crossover will show lights, but no actual layer 2 comms
go...


> One ip is set to 192.168.0.1 and the other, 192.168.0.2 and both are
> in netmask 255.255.255.0.
>

I am not sure if the `arp` command is installed by default on your
system/ubuntu, but on my system it shows all the systems that have
broadcasted an arp, and AFAIK, arps are not blocked by any firewalls (as
they almost always work on layer 3, rather than Layer 2 where the MAC
address resides).  I would check that.  Also check `arping`.  Since arps are
usually not firewalled, this "ping" should overcome any firewall issues.  DO
not think that SELinux works at L2 either, so that should verify raw
connectivity.


> No response from ping on ether end. Ifconfig shows the eth0 is up with
> static set ips.
>

Local box pings work? You could use tcpdump/wireshark to check for activity
on the wire as well...


> --
> Christopher Lemire <christopher.lemire at gmail.com>
> Ubuntu 64 bit Linux Raid Level 0
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