I have an azure Linux VM say VM1 having only one network interface with private IP 10.3.0.5, I have another azure Linux VM say VM2 with two network interfaces, the private IP on primary network interface is 10.3.5.4, the private IP on the secondary network interface is 10.3.4.4.
Now I am able to ping VM2 from VM1 on primary network interface of VM2 as
ping 10.3.5.4 but I am not able to ping it in on secondary network interface as ping 10.3.4.4.
After reading azure docs - https://learn.microsoft.com/en-gb/azure/virtual-machines/linux/multiple-nics#configure-guest-os-for-multiple-nics, they say that you would have to manually add required routes to achieve this.
Similar problem in windows VM - https://support.microsoft.com/en-in/help/4048050/troubleshooter-for-azure-vm-connectivity-problems
here is the result of command route -n on VM2
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 10.3.5.1 0.0.0.0 UG 0 0 0 eth0
10.3.4.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
10.3.5.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
168.63.129.16 10.3.5.1 255.255.255.255 UGH 0 0 0 eth0
169.254.169.254 10.3.5.1 255.255.255.255 UGH 0 0 0 eth0
172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
172.18.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker_gwbridge
Now as per the above azure docs, it is missing an entry something like this
0.0.0.0 10.3.4.1 0.0.0.0 UG 0 0 0 eth1
I tried adding this route to my VM2 but after running the following command, my vm just stopped responding
route add -net 0.0.0.0 netmask 0.0.0.0 gw 10.3.4.1 dev eth1
How do I add the correct route for my problem ? Please help !
Copyright License：
Author:「Aak」,Reproduced under the CC 4.0 BY-SA copyright license with link to original source & disclaimer.
Link to：https://stackoverflow.com/questions/56802924/unable-to-communicate-from-one-azure-vm-in-same-virtual-net-to-the-secondary-nic