Re: [Sheflug] Network Goes on Holiday

["Chris J/#6" <nospam [at] nccnet.co.uk>]

> 
> Yeh, did that at first but forgot to send it in :-(
> On the SuSE machine........
> 
> Kernel IP routing table 
> Destination Gateway   Genmask     Flags MSS Window irtt Iface 
> 192.247.47.47 *   255.255.255.255  UH    0 0        0    ippp0 
> 192.168.0.0   *   255.255.255.0    U     0 0        0    eth0 
> loopback      *   255.0.0.0        U     0 0        0    lo
> 
> on the Debian box......
> 
> Destination    Gateway   Genmask     Flags  MSS Window   irtt Iface
> 192.168.1.0    *      255.255.255.0  U       0   0        0    eth0
> 192.247.0.0    *      255.255.0.0    U       0   0        0    ippp0
> 127.0.0.0      *      255.0.0.0      U       0   0        0    lo
> 

Okay...first of, both machines are on different subnets - look at the routes. 
The SuSE box has a route for 192.168.0.0, netmask 255.255.255.0 (which I'll 
write now as 192.168.0.0/24) - the debian 192.168.1.0 netmask 255.255.255.0 
(aka 192.168.1.0/24).

As you have a 24 bit netmask, the first three octets of the IP address 
identify the network (or subnet), ie, 192.168.0 for the SuSE and 192.168.1 
for the Debian. The only way you can get both machines to talk is if they are 
on the same subnet - so there are two ways to do this:
	1. Change the IP address so they're both on the same subnet
	2. Change the netmask to a 16-bit netmask (ie, netmask 255.255.0.0)

Another thing to be wary of is that Linux won't forward packets (ie, it won't 
route packets between two different network devices) unless you do (kernel 
2.2 ... 2.0 I don't think has this problem ... no idea about 2.3, 2.4):
	echo 1 > /proc/sys/net/ipv4/ip_forward
which may also be catching you out. Usually this is done by default, however 
I've been told Redhat has doesn't do this by default. Stick it in rc.local 
(or similar) to sort this out :)

SuSE should be easy to fix - all its interface config is in /etc/rc.config 
and routing in /etc/route.conf. I've not touched Debian so can't comment on 
how to config that.

rc.config - interested parts: IPADDR_0, NETDEV_0 and IFCONFIG_0 - these will 
all define the first physical ethernet card (IP address, physical device (eg, 
eth0) and ifconfig command line parameters respectively).

route.conf - line based, straight forward to change. Just make sure the 
netmask field matches the netmask given to the interface. There are 
exceptions to this, but its when your doing clever networking stuff :) To be 
safe, make sure it matches.

Chris...


-- 
@}-,'--------------------------------------------------  Chris Johnson --'-{ [at] 
    / "(it is) crucial that we learn the difference / sixie [at] nccnet.co.uk  \
   / between Sex and Gender. Therein lies the key  /                       \ 
  / to our freedom" -- LB                         / www.nccnet.co.uk/~sixie \ 


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