How to switch generic routing to source routing?

Question

I will need to do source routing and before going into more complicated setups I want to understand how this works by switching the generic routing (the one created magically by the networking setup) into a source routed one.

The goal is to create a specific routing table and set an ip rule to route traffic from my IP through this routing table (which is, as far as I understand, what happens with the default table). This is on a Debian 8 with one interface to which is assigned the IP 192.168.1.107.

The problem is that this cloning does not work.

I first created an new entry in /etc/iproute2/rt_tables

200 NORMAL

I then dumped the current routing table - for a working networking

root@debian-testing:~# ip route show table all
default via 192.168.1.1 dev eth0
169.254.0.0/16 dev eth0  scope link  metric 1000
192.168.1.0/24 dev eth0  proto kernel  scope link  src 192.168.1.107
broadcast 127.0.0.0 dev lo  table local  proto kernel  scope link  src 127.0.0.1
local 127.0.0.0/8 dev lo  table local  proto kernel  scope host  src 127.0.0.1
local 127.0.0.1 dev lo  table local  proto kernel  scope host  src 127.0.0.1
broadcast 127.255.255.255 dev lo  table local  proto kernel  scope link  src 127.0.0.1
broadcast 192.168.1.0 dev eth0  table local  proto kernel  scope link  src 192.168.1.107
local 192.168.1.107 dev eth0  table local  proto kernel  scope host  src 192.168.1.107
broadcast 192.168.1.255 dev eth0  table local  proto kernel  scope link  src 192.168.1.107

I moved entries related to the real interface (192.168.1.107) to table NORMAL (what is below is the content of a file t.txt which will be parsed in a moment)

root@debian-testing:~# cat t.txt
local 127.0.0.0/8 dev lo  table local src 127.0.0.1
local 127.0.0.1 dev lo  table local  src 127.0.0.1
local 192.168.1.107 dev eth0  table NORMAL src 192.168.1.107
192.168.1.0/24 dev eth0 src 192.168.1.107 table NORMAL
broadcast 127.0.0.0 dev lo  table local src 127.0.0.1
broadcast 127.255.255.255 dev lo  table local  src 127.0.0.1
broadcast 192.168.1.0 dev eth0  table NORMAL src 192.168.1.107
broadcast 192.168.1.255 dev eth0  table NORMAL src 192.168.1.107
default via 192.168.1.1 dev eth0 table NORMAL

I then flushed all existing routing entries, loaded the ones above and informed the system that packets from 192.168.1.107 should use the table NORMAL

root@debian-testing:~# ip route flush table all ; while read name; do echo "adding ${name}";ip route add ${name}; done < t.txt ; ip rule add from 192.168.0.107 table NORMAL
adding local 127.0.0.0/8 dev lo  table local src 127.0.0.1
RTNETLINK answers: Invalid argument
adding local 127.0.0.1 dev lo  table local  src 127.0.0.1
adding local 192.168.1.107 dev eth0  table NORMAL src 192.168.1.107
adding 192.168.1.0/24 dev eth0 src 192.168.1.107 table NORMAL
adding broadcast 127.0.0.0 dev lo  table local src 127.0.0.1
adding broadcast 127.255.255.255 dev lo  table local  src 127.0.0.1
adding broadcast 192.168.1.0 dev eth0  table NORMAL src 192.168.1.107
adding broadcast 192.168.1.255 dev eth0  table NORMAL src 192.168.1.107
adding default via 192.168.1.1 dev eth0 table NORMAL

Unfortunately now I cannot reach neither le local IP, nor an external host anymore, even though the routing table has been repopulated. The only ping which goes through is to 127.0.0.1.

root@debian-testing:~# ping 8.8.8.8
connect: Network is unreachable
root@debian-testing:~# ping 192.168.1.107
connect: Network is unreachable
root@debian-testing:~# ip route
root@debian-testing:~# ip route show table all
default via 192.168.1.1 dev eth0  table NORMAL 
broadcast 192.168.1.0 dev eth0  table NORMAL  scope link  src 192.168.1.107 
192.168.1.0/24 dev eth0  table NORMAL  scope link  src 192.168.1.107 
local 192.168.1.107 dev eth0  table NORMAL  scope host  src 192.168.1.107 
broadcast 192.168.1.255 dev eth0  table NORMAL  scope link  src 192.168.1.107 
broadcast 127.0.0.0 dev lo  table local  scope link  src 127.0.0.1 
local 127.0.0.1 dev lo  table local  scope host  src 127.0.0.1 
broadcast 127.255.255.255 dev lo  table local  scope link  src 127.0.0.1 

Where should I be looking for to fix this? Is my approach correct at all?

Answer 1

It all seems correct, except you are not specifying the interface to use for the communication. Try

ping -I 192.168.1.107 -c1 8.8.8.8

and it should work.