How to cusomize docker0 in Docker for different IP range? - networking

Question

I am referring Docker Networking#docker0 for customizing docker0 virtual bridge in Docker.
My ifconfig shows this:
docker0 Link encap:Ethernet HWaddr d6:0d:76:37:ee:04
inet addr:172.17.42.1 Bcast:0.0.0.0 Mask:255.255.0.0
inet6 addr: fe80::d40d:76ff:fe37:ee04/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:648 (648.0 B)
eth0 Link encap:Ethernet HWaddr 08:00:27:51:e4:40
inet addr:10.0.2.15 Bcast:10.0.2.255 Mask:255.255.255.0
inet6 addr: fe80::a00:27ff:fe51:e440/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:947 errors:0 dropped:0 overruns:0 frame:0
TX packets:618 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:86885 (86.8 KB) TX bytes:71855 (71.8 KB)
I want to give range 10.0.2.15/24 to docker0 interface.
Note:
I am assuming that if I customize docker0 with same IP range as that of eth0 then containers should get IPs from same range.(Please correct me if I am assuming wrong).
For this, I tried adding --fixed-cidr=10.0.2.15/24 in /etc/default/docker file. But it is now working.
Any idea how to achieve it?
Also, if I am following wrong way, please guide me how to achieve it in proper way.

Answer 1

Instead of changing the ip-range of your docker0 interface, you should think about what you want to be available to the outside.
If you want certain ports to link to your application and be available from the outside, take a look at the -p flag.
docker run -p IP:host_port:container_port
Take a look at the documentation for network configuration http://docs.docker.com/articles/networking/
This documentation also explains how to change the ip-range of the docker0 interface. However I think thre are other, better and easier ways to achieve what you want.
(Could you explain exactly what you want by the way?)

Answer 2

What you are trying to do is bordering networking suicide... If docker would let you assign your external NIC-IP (eth0) to the internal bridging-interface (docker0) your system would have two interfaces working on the same route but with different networks behind the interface. Try to think about a post-man who is working in a city and some genius gave all the streets the same name and they all started counting the numbers at 1. Could he deliver any mail? ;)
What I assume you want to achieve is, to be able to connect to whatever your docker container is running, from the "outside"-network. In that case simply add
-p port_on_host:port_inside_container
to your
docker run-command and your docker-content becomes available to the outside world via your host-ip (if your firewall is properly set up)
Cheers
D

Answer 3

i think you should delete docker0 bridge and create docker0 bridge by giving subnet of own .
for more pratical view and images visit : https://support.zenoss.com/hc/en-us/articles/203582809-How-to-Change-the-Default-Docker-Subnet