Connectivity between v-net-0 and eth0 in CKA course

Certified Kubernetes Administrator
#1

In the CKA course, under the Networking section, specifically the Network Namespace lesson, it’s mentioned that to establish connectivity between a virtual bridge (v-net-0) and the host interface (eth0), we need to assign an IP address such as 192.168.15.5 to v-net-0, which belongs to the 192.168.15.0/24 subnet. Once this is done, pinging the network namespace (e.g., at 192.168.15.1) starts working.

Since v-net-0 is effectively another network interface on the host (i.e., it exists alongside eth0), wouldn’t we also need to enable IP forwarding on the host to allow communication between the two interfaces? Specifically, by adding the following line to /etc/sysctl.conf:

net.ipv4.ip_forward = 1
#2

I’m not sure why this is, but it does not. Creating a bridge interface works fine without setting up ip_forward, for whatever reason.

#3

Oh! Does that mean only physical interface need ip_forward forwarding to communicate with each other?
Not virtual interface which is of type bridge in this case ?

#4

As near as I can tell, yes. I think that the ip_forward setting is used if the host is acting to route packets between hosts. Interfaces within the same host work without that.

#5

In same networking section, it is mentioned that to convert host B into router and allow it to forward traffic from interface eth0 to interface eth1 , we should add ip_forward