mjhjmtu

I have an Ubuntu based server with 4 Ethernet interfaces (eth0, eth1, eth2, eth3). Eth0 from network 192.168.0.0/24 is having a fixed IP address 192.168.0.19 and GW: 192.168.0.254 and eth1 to eth3 are in a bridge mode with br0 IP: 10.0.0.3, net: 10.0.0.0/24, gw: 10.0.0.254. The server is connected to the outside network either over eth0 or eth3 port. I want in case that eth0 is UP the server to have default GW from 192.168.0.0/24 network and if eth3 is UP to have default GW from 10.0.0.0/24 network. I have tried to add two routing tables /etc/iproute2/rt_tables:

# reserved values
#
255 local
254 main
253 default
0 unspec
#
# local
#
#1 inr.ruhep
2 rt1
3 rt2

and changed the /etc/network/interfaces file adding post-up and post-down rules as follows:

post-up ip route add 192.168.0.0/24 dev eth0 src 192.168.0.19 table rt2
post-up ip route add default via 192.168.0.254 dev eth0 table rt2
post-up ip rule add from 192.168.0.19/32 table rt2
post-up ip rule add to 192.168.0.19/32 table rt2
post-up ip r add default via 192.168.0.254 metric 101 dev eth0
post-down ip rule del from 0/0 to 0/0 table rt2
post-down ip rule del from 0/0 to 0/0 table rt2

and for eth3:

post-up ip route add 10.0.0.0/24 dev eth3 src 10.0.0.3 table rt1
post-up ip route add default via 10.0.0.254 dev eth3 table rt1
post-up ip rule add from 10.0.0.3/32 table rt1
post-up ip rule add to 10.0.0.3/32 table rt1
post-up ip r add default via 10.0.0.254 metric 100 dev eth3
post-down ip rule del from 0/0 to 0/0 table rt1
post-down ip rule del from 0/0 to 0/0 table rt1

The problem is that the Linux server isn't reading these rules from the interfaces config file and when I execute ip rule show it is showing me the rt1 and rt2 routing tables in its output. If I add these rules manually it was listing them correctly, but for some reason the automatic routing was not working correctly, and the device was not deleting the default gw and only adding the new one. I was mostly following another thread here: Is it possible to have multiple default gateways for outbound connections?. I know that I can write a bash script which will check the status of the two ports at regular intervals and then delete and add the appropriate routes but I think this is not so elegant solution since this script has to work always in the background and it will add some latency to the execution, which will be maximum the configured polling time. I really like the solution based on the post-up/post-down but I can't make it work correctly on my machine.