Docker Default IP Query

General Discussions
1

Hi,

I run a selection of game servers for counter-strike and log all IP’s that join. I’ve recently had to ban somebody and they were using the IP ‘172.17.42.1’. A quick google search says this relates to Docker. A number of players have been using this IP. Could someone explain the context as to why multiple players would have this IP? What does this have in relation to Docker?

Is this the same person or multiple people?

2

There are a few IP address ranges that are reserved for private use. For example,

NetRange:       192.168.0.0 - 192.168.255.255
CIDR:           192.168.0.0/16
NetName:        PRIVATE-ADDRESS-CBLK-RFC1918-IANA-RESERVED

and

NetRange:       10.0.0.0 - 10.255.255.255
CIDR:           10.0.0.0/8
NetName:        PRIVATE-ADDRESS-ABLK-RFC1918-IANA-RESERVED

Another private address range, but less known, is the following:

NetRange:       172.16.0.0 - 172.31.255.255
CIDR:           172.16.0.0/12
NetName:        PRIVATE-ADDRESS-BBLK-RFC1918-IANA-RESERVED

Part of Docker’s network model is to set up a mini private NAT’d network for the virtual interfaces that are used to give each container its own network device. The 172.17.42.1 address happens to be one of the commonly chosen addresses for the gateway bridge. (this ip is chosen at runtime by the docker daemon). Due to the NATing, it is possible that a gameserver running in docker would see the gateway’s IP instead of the end user’s real IP.

Is this gameserver running in docker?