customizing docker bridge network - docker

Question

I want my docker0 and all containers to have the same gateway address or be in the same IPrange as my local machine. I started by defining a fixed-cidr in ther daemon.json file /etc/docker/daemon.json
{
"bip": "10.80.44.248/24",
"fixed-cidr": "10.80.44.250/25",
"mtu": 1500,
"default-gateway": "10.80.44.254",
"dns": ["10.80.41.14"]
}
It seems to be working looking at the output of the ip -a
It seems the docker0 has never received any data since.
docker0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet *10.80.44.248* netmask 255.255.255.0 broadcast *10.80.44.255*
ether 02:42:9c:b9:e1:63 txqueuelen 0 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
ens192: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet *10.80.44.39* netmask 255.255.255.0 broadcast *10.80.44.255*
inet6 fe80::250:56ff:feb1:79e4 prefixlen 64 scopeid 0x20<link>
ether 00:50:56:b1:79:e4 txqueuelen 1000 (Ethernet)
RX packets 211061 bytes 30426474 (29.0 MiB)
RX errors 0 dropped 33861 overruns 0 frame 0
TX packets 3032 bytes 260143 (254.0 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
The local machine and the docker0 are in same IP range with the same gateway. Good.
But when I start the docker containers and inspected the bridge settings Everything was different. This is the output of
docker network inspect bridge
[
{
"Name": "bridge",
"Id": "b326a37a589245449e1268bbb9ee65262eb7986574c0e972c56d350aa82d7238",
"Created": "2018-04-04T03:25:52.00544539+02:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "10.80.44.248/24",
"IPRange": "10.80.44.128/25",
"Gateway": "10.80.44.248",
"AuxiliaryAddresses": {
"DefaultGatewayIPv4": "10.80.44.254"
}
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {},
"Options": {
"com.docker.network.bridge.default_bridge": "true",
"com.docker.network.bridge.enable_icc": "true",
"com.docker.network.bridge.enable_ip_masquerade": "true",
"com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
"com.docker.network.bridge.name": "docker0",
"com.docker.network.driver.mtu": "1500"
},
"Labels": {}
}
]
I don't understand why now IPAM config is having a IPv4 als auxiliary
"AuxiliaryAddresses": {
"DefaultGatewayIPv4": "10.80.44.254"
}
I realised that now the bridge is not created from the same subnet as it was configured by the daemon I it created 2 different bridges with different IP ranges. That is still the default from docker.
docker network ls
NETWORK ID NAME DRIVER SCOPE
b326a37a5892 bridge bridge local
6ce11066cdea dockergitlab_default bridge local
d5a36c04b809 host host local
15f66b88ee67 none null local
docker network inspect dockergitlab_default
[
{
"Name": "dockergitlab_default",
"Id": "6ce11066cdeabf3cfe65b2dff22046bd1e9c18d2588f47b9cd3c52ea24f7a636",
"Created": "2018-03-14T08:56:23.351051727+01:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.17.0.0/16",
"Gateway": "172.17.0.1"
}
]
},
"Internal": false,
"Attachable": true,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {
"60f769c91cff1de47794a7c8b587b778488883da094ae32cfde5196ee0f528f1": {
"Name": "gitlab-runner",
"EndpointID": "5122fe862537fb8434a484b4797153274b945e20bc3c7223efc6fd0bd55eae14",
"MacAddress": "02:42:ac:11:00:04",
"IPv4Address": "172.17.0.4/16",
"IPv6Address": ""
},
"9c46e1fde6390142bddf67270cfeda7b3e68b1a6e68cabc334046db687240a8d": {
"Name": "dockergitlab_postgresql_1",
"EndpointID": "8488b32cc34a2c92308528de74b5eddcecac12a402ee6e67c1ef0f2750b72721",
"MacAddress": "02:42:ac:11:00:03",
"IPv4Address": "172.17.0.3/16",
"IPv6Address": ""
},
"eaf29f5f405cbf9bdd918efad26ceae1a8c3f58f4bef0aa8fd86b4631bcfdf43": {
"Name": "dockergitlab_gitlab_1",
"EndpointID": "d7f78ee9bd51dd13826d7834470d03a9084fc7ab8c6567c0181acecc221628c6",
"MacAddress": "02:42:ac:11:00:02",
"IPv4Address": "172.17.0.2/16",
"IPv6Address": ""
},
"f460687ec00eff214fa08adfe9a0af5b85c392ceb470c4ed630ef7ecb0bfcba1": {
"Name": "dockergitlab_redis_1",
"EndpointID": "8b18906f1c79a5faaadd32afdef20473f9b635e9a1cd2c7108dd98df48eaed86",
"MacAddress": "02:42:ac:11:00:05",
"IPv4Address": "172.17.0.5/16",
"IPv6Address": ""
}
},
"Options": {},
"Labels": {
"com.docker.compose.network": "default",
"com.docker.compose.project": "dockergitlab"
}
}
]
I have no idea why the docker bridge is now created with the old default ip address.
LOCAL SYSTEM Details
I can do apt update on the local machine but when i logged into the gitlab-runner i can't do apt update
Linux 4.9.0-6-amd64 #1 SMP Debian 4.9.82-1+deb9u3 (2018-03-02) x86_64
Docker version 17.12.0-ce, build c97c6d6
docker-compose version 1.18.0, build 8dd22a9
Is there a way I can oveeride the bridge settings. From what i have read, when I define/configure the cdir and gateway in daemon.json file everything will be taken from there for the creation of the bridge network and all other containers.
Thanks in Advance for your help.

Answer 1

First of all you've correctly configured the docker0 bridge and starting containers with the plain docker run command should connect them to the bridge and give them IPs in 10.80.44.250/25.
From what you've pasted I guess you're using docker-compose to start your containers.
docker-compose will create a myproject_default network per docker-compose.yml if you don't specify anything.
Today you cannot choose in which pool the IP ranges will be chosen, it's by default a 172.[17-31].0.0/16. There is currently an active pull request to allow override of this behaviour : https://github.com/moby/moby/pull/36396.
If you want to manually specify the IP range in your docker-compose.yml you can write this :
networks:
default:
ipam:
config:
- subnet: 10.80.44.250/25
Edit : this is only compatible with a docker-compose syntax >=3.0.