ip route add: RTNETLINK answers: Network is down

Question

I'm quite new to networking and I really can't figure this out.

I am trying to add a static route so that all traffic to aa.aa.aa.aa goes through eth0:0 interface

 root@LSW-199:~# ifconfig
 eth0      Link encap:Ethernet  HWaddr 80:c1:6e:6f:f8:68  
           inet addr:xx.xx.xx.xx  Bcast:xx.xx.xx.xx  Mask:255.255.255.224
           inet6 addr: fe80::82c1:6eff:fe6f:f868/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:93598294 errors:0 dropped:0 overruns:0 frame:0
           TX packets:95074908 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000 
           RX bytes:23532770742 (23.5 GB)  TX bytes:27395117749 (27.3 GB)
           Memory:c0400000-c0420000 

 eth0:0    Link encap:Ethernet  HWaddr 80:c1:6e:6f:f8:68  
           inet addr:bb.bb.bb.bb  Bcast:xx.xx.xx.xx  Mask:255.255.255.192
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Memory:c0400000-c0420000 

 lo        Link encap:Local Loopback  
           inet addr:127.0.0.1  Mask:255.0.0.0
           inet6 addr: ::1/128 Scope:Host
           UP LOOPBACK RUNNING  MTU:65536  Metric:1
           RX packets:107 errors:0 dropped:0 overruns:0 frame:0
           TX packets:107 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0 
           RX bytes:9416 (9.4 KB)  TX bytes:9416 (9.4 KB)

The eth0:0 is definitely working because when I use cURL to test it can successfuly use the device and the IP is correct:

 root@LSW-199:~# curl --interface eth0:0 api.ipify.org
 bb.bb.bb.bb

But when I try to add a static route I get this error message:

 root@LSW-199:~# ip route add aa.aa.aa.aa via bb.bb.bb.bb
 RTNETLINK answers: Network is down

I have tried it service networking restart and ifconfig eth0:0 down/up with no luck.

Any ideas?

quadruplebucky · Answer 1 · 2017-06-12T00:32:01.917

Ok after actually trying some of this ...

ip addr add aa.aa.aa.aa/24 dev eth0 label eth0:0
ip addr add dd.ad.aa.aa/27 dev eth0 label eth0:1
ip addr add gg.gg.gg.gg/14 dev eth0 label eth0:2
ip addr add 9.23.23.23/8 dev eth0 label eth0:3

All that's fine, and my machine thinks it's now on IBM's /8.

But there's actually no functional difference between eth0, eth0:0, eth0:1, eth0:2, eth0:3 that I can see. "ip route" and "netstat -nr" don't distinguish between the interfaces, they both report eth0. (although route and " ip route will accept the eth0:X alias label as a dev argument). "tcpdump -ni eth0" and "tcpdump -ni eth0:2" send and recieve the same traffic...however, if I do this

ip route replace to 9.23.23.23/8 src dd.ad.aa.aa dev eth0:1

my (unsuccessful) pings to 9.23.23.23.2 now appear to coming from my alias IP dd.ad.aa.aa. Which if I'm not mistaken, is what you were trying to accomplish before I distracted you with a bunch of irrelevant and wrong thinking.

I hope this helps.

The first one is giving me this error: `SIOCADDRT: No such device` The second is giving me this error: `route: netmask doesn't match route address` My eth0:0 interface has a different netmask, could this cause any problems? — samgreeneggsham, Jun 11 '17 at 13:20
I can get the route added but the problem is if I try to connect I get this error message `No route to host` also when I execute `route -n` it says **eth0** under the **Use Iface** section instead of **eth0:0** — samgreeneggsham, Jun 11 '17 at 23:32

score 0 · Answer 2 · answered Jun 13 '17 at 10:59

I solved this by having to add the gateway in the route command.

route add -net aa.aa.aa.aa netmask 255.255.255.255 gw 199.115.112.190 dev eth0:0

I think the reason is that eth0:0 is on a different gateway to eth0 but it tries to route it through that, I'm not too sure if this is the reason but they are definitely on different gateways and it definitely solved it.

ip route add: RTNETLINK answers: Network is down

2 Answers2