Unable to add route with a specific gateway IP

Linux and Unix-Like Linux
1

Hi,

This is the routing table on a RHEL 7 server :

[root@SIEMsmartcon3 ~]# route -n
Kernel IP routing table
Destination	Gateway		Genmask		Flags	Metric	Ref	Use Iface
0.0.0.0		10.132.81.145	0.0.0.0		UG	100	0	0   eno49
10.132.81.144	0.0.0.0		255.255.255.240	U	100	0	0   eno49
169.254.0.0	0.0.0.0		255.255.0.0	U	100	0	0   eno49		
169.254.0.0	0.0.0.0		255.255.0.0	U	1003	0	0   eno50

I tried to add a route like this, however as shown an error is thrown :

[root@SIEMsmartcon3 ~]# ip route add 10.132.81.160/28 via 10.132.81.161 dev eno50
RTNETLINK answers: Network is unreachable

The 10.132.81.161 gateway is used as a gateway for another interface in the server (eno50).
Why is the error above thrown when I try to add that line? Is it because that gateway is not initiated as a default gateway in the routing table?

2

Are you sure you want to add the network on that host? The ...160 is outside your subnet, so you must route through ...145 , the default gateway. Please post the output of arp -a or arp -e of the two nodes on your LAN segment.

3

Hi,

Thank you for your reply. However, there are no two servers involved, only one. These are the outputs requested :

[root@SIEMsmartcon3 ~]# arp -a
? (10.132.81.164) at 00.17:a4:77;a4:56 [ether] on eno50
? (10.132.81.162) at ec:eb:b8:9f:01:26 [ether] on eno50
? (10.132.81.161) at 00:10:db:ff:20:04 [ether] on eno50 gateway (10.132.81.145) at 00:10:db:ff:20:04 [ether] on eno49
? (10.132.81.147) at 00:17:a4:77:a4:52 [ether] on eno49

[root@SIEMsmartcon3 ~]# arp -e
Address		HWtype	HWaddress		Flags Mask	Iface
10.132.81.164	ether	00:17:a4:77:a4:56	C		eno50
10.132.81.162	ether	ec:eb:b8:9f:01:26	C		eno50
10.132.81.161	ether	00:10:db:ff:20:04	C		eno50
gateway		ether	00:10:db:ff:20:04	C		eno49
10.132.81.147	ether	00:17:a4:77:a4:52	C		eno49

Best Regards,
anaigini45

4

I'm a bit puzzled. Did you use "alias interfaces", as both seem to share the same MAC address? Pls show the output from ifconfig or its ip equivalent.

5

According to your routing table the IP-Network for the gateway (10.132.81.161) is connected via NIC eno50 . But the route-setup command points to NIC eno49 .

Maybe you should just omit the dev eno50 in your route command or change your ip configuration so that 10.31.181... is configured to eno50 instead of eno49.

And yes /28 is smaller than expected. As RudiC said the gateway is outside your subnet anyway. The gateway must be located within one of the configured subnets of your server.