Multiple NIC, no ping

November 16, 2017 680 views
Networking Ubuntu 16.04

Ubuntu server 16.04, fresh install on x64.
Here the topology:

internet router (192.168.1.254) ---- enp0s7 (192.168.1.69)
host (192.168.0.70) ----- enp1s8 (192.168.0.69)

Internet works ok but I can't ping 192.168.0.70, only arp ping.

/etc/network/interfaces (note the comments):

The primary network interfaceauto enp0s7

iface enp0s7 inet static
address 192.168.1.69
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.254
dns-nameservers 8.8.8.8 8.8.4.4

The GRAF net network interface

auto enp1s8
iface enp1s8 inet static
address 192.168.0.69
netmask 255.255.255.0
network 192.168.0.0
broadcast 192.168.0.255

gateway 192.168.0.70

metric 400

up route add -net 192.168.0.0/24 dev enp1s8

results from route -n:

Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.1.254 0.0.0.0 UG 0 0 0 enp0s7
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 enp1s8
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 enp0s7

results from arp-scan on enp1s8 interface:

Interface: enp1s8, datalink type: EN10MB (Ethernet)
Starting arp-scan 1.8.1 with 256 hosts (http://www.nta-monitor.com/tools/arp-scan/)
192.168.0.70 00:0c:42:fa:05:e2 Routerboard.com
1 packets received by filter, 0 packets dropped by kernel
Ending arp-scan 1.8.1: 256 hosts scanned in 1.453 seconds (176.19 hosts/sec). 1 responded

I think doesn't matter but ipforward is YES.

Why I can't reach on level 3 host 192.168.0.70? What I'm doing wrong?
I think for what I know and what I read on the web this is the right configuration...doesn't work also uncommenting "up route add -net 192.168.0.0/24 dev enp1s8"

1 Answer

192.168.0.0 is a local only subnet so you won't be able to ping out or in to it.

Only other hosts on the same subnet would be able to ping each other. That is why you are having the issue.

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