fighting with router tables

[robert rottermann]

Hi there

I have an ubuntu box.

Attached to it are two raspberries.
Each of the raspberries can be reached trough two interfaces:eth0, tun0.
Eventually the raspberries will be placed in the ""wild" and only tun0 will be 
accessible.

No my problem:
Access to one of the two raspberry is fast,to the other one it is very slow.

When I look at the routing table the following is presented:

FAST raspberry:
---------------
spsconnect at spsconnecttest ~/spsControl $ route -n
Kernel-IP-Routentabelle
Ziel            Router          Genmask         Flags Metric Ref    Use Iface
0.0.0.0         0.0.0.0         0.0.0.0         U 0      0        0 ppp0
10.42.0.0       10.146.176.200  255.255.255.0   UG 0      0        0 tun0
10.64.64.64     0.0.0.0         255.255.255.255 UH 0      0        0 ppp0
10.146.176.0    10.146.176.200  255.255.255.0   UG 0      0        0 tun0
10.146.176.200  0.0.0.0         255.255.255.255 UH 0      0        0 tun0
10.168.0.0      0.0.0.0         255.255.255.0   U 0      0        0 eth0

SLOW raspberry:
---------------
spsconnect at spsconnect2 ~/spsControl $ route -n
Kernel-IP-Routentabelle
Ziel            Router          Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.168.0.1      0.0.0.0         UG    0 0        0 eth0
10.42.0.0       10.146.176.202  255.255.255.0   UG    0 0        0 tun0
10.64.64.64     0.0.0.0         255.255.255.255 UH    0 0        0 ppp0
10.146.176.0    10.146.176.202  255.255.255.0   UG    0 0        0 tun0
10.146.176.202  0.0.0.0         255.255.255.255 UH    0 0        0 tun0
10.168.0.0      0.0.0.0         255.255.255.0   U     0 0        0 eth0


The only difference (next to the ips 10.146.176.200 and 10.146.176.202)
is the default route:
0.0.0.0         10.168.0.1      0.0.0.0         UG 0      0        0 eth0

10.168.0.1 is the ip of the modem trough which I access the internet.


Now my questions:
"what" processes are setting these routes? I "did nothing" .. (or maybe I did 
but can not remeber)
Would not the "slow" configuration with the modem as default gateway be correct?


And:
I really need to come to speed with routing et al.
Can anybody point me to a tutorial that would help (covering "middle" ground, 
not too basic and not to exotic..)


thanks
robert