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Luis
Asked: 2017-02-14 03:43:22 +0800 CST

Not able to delete one of default routes

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In my Linux server (4.9.9_1 kernel, x86_64) enp5s0 has a static ip 192.168.1.30 and enp9s0 is given an address via dhcpcd.

# ip route ls
default via 192.168.1.1 dev enp5s0 src 192.168.1.30 metric 202 
default via 39.53.131.254 dev enp9s0 src 39.53.131.237 metric 203 
39.53.130.0/23 dev enp9s0 proto kernel scope link src 39.53.131.237 metric 203 
192.168.1.0/24 dev enp5s0 proto kernel scope link src 192.168.1.30 metric 202

The first thing I don't understand is why does the system set two default routes, although preference is given to one based on metric.

What I want to do is to delete the second default route via 39.53...., to add another routing table, set ip rule for that to add an identical default route but for the new routing table.

When:

# ip route del default via 39.53.131.254 dev enp9s0
# echo $?
0

The routing table doesn't seem to have changed, though:

    # ip route l
    default via 192.168.1.1 dev enp5s0 src 192.168.1.30 metric 202 
    default via 39.53.131.254 dev enp9s0 src 39.53.131.237 metric 203
39.53.130.0/23 dev enp9s0 proto kernel scope link src 39.53.131.237 metric 203 
192.168.1.0/24 dev enp5s0 proto kernel scope link src 192.168.1.30 metric 202

After a ip route flush cache:

# ip route show cache

shows nothing.

What should I do?

linux routing networking

2 Answers

  1. After help on Freenode IRC ##linux channel. As dhcpcd was responsible for the IP address of enp9s0, the way to clear the routes passing through the interface is to flush the device: ip addr flush dev enp9s0.

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  2. Interestingly, but many years after, I bumped into similar situation n Debian Buster.

    There where constantly something messing up with my default routes, and the reason was systemd connman.service.

    Finally I found logs:

    journalctl -n -u connman.service
br0 {add} route 192.168.1.0 gw 0.0.0.0 scope 253 <LINK>
br0 {add} route 0.0.0.0 gw 192.168.1.1 scope 0 <UNIVERSE>
enp5s0 {add} address 169.254.208.64/16 label enp5s0 family 2
enp5s0 {add} route 169.254.0.0 gw 0.0.0.0 scope 253 <LINK>
enp5s0 {add} route 0.0.0.0 gw 0.0.0.0 scope 253 <LINK>

    and thats it, internet is gone.

    Fixed by totally removing service:

    systemctl stop connman.service
systemctl disable connman.service
systemctl mask connman.service
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