[SC.LUG] networking for idiots

[Robert Marshall]

On Mon, 4 Apr 2005, Srdjan Todorovic wrote:

> Hello Robert
> 
Thanks for this - and good to see you at Wheelock!

> --- Robert Marshall
> <robert at chezmarshall.freeserve.co.uk> wrote:
>> I'm trying to connect two linux boxes together and
>> currently getting
>> nowhere, so I thought I offer the current situation
>> here for analysis/mockery.
> 
>> >From here I'm connected to the internet fine (eth0)
>> and am trying to use
>> eth1 to get to another machine via a cross-over, but
>> I can't ping it or ssh
>> or anything
> 
> Re-verify host A and host B IP addresses.

appears ok

> 
> You can try ping -b to ping the broadcast address, and
> then use Ethereal or tcpdump to find if any IP/ICMP
> traffic is being sent back from the other host.

# tcpdump -i eth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
21:26:33.795534 arp who-has 192.168.0.54 tell 192.168.0.53
21:26:34.794551 arp who-has 192.168.0.54 tell 192.168.0.53
21:26:35.794361 arp who-has 192.168.0.54 tell 192.168.0.53
etc

doesn't appear so

> 
> What you've shown seems to be ok. Might be problem
> with
> lower part of the stack than IP. Have you got the
> Ethernet link lights on?
> 

ohh that's difficult to get to, one of them is integrated with the m/b but
and the other needs the table taking out...maybe I'll have to do some digging!

> Re-check that both hosts have their interface up.
> 

Yes

> You might want to disconnect from Internet, and
> iptables -F from both hosts, to clear firewall rules
> (in case that's the problem).

I've cleared iptables from the non-internet connected machine without any
improvement and checked /var/log/messages on the other machine without seing
anything, but maybe the next step is to unplug

ISTR having difficulties with persuading eth1 to come up on this machine
with mdk 9.2 and thought (after googling) it was probably the driver on
that release (this was talking to a laptop which had worked on eth0 before
I started using eth0 for broadband) but with mdk 10.1 eth1 comes up without
any apparent problems - it appears to use a different module with this
release - was tulip(I think?) now 3c59x

Robert
-- 
Links and things http://rmstar.blogspot.com/
Robert Marshall