Tag: networking

How does docker0 bridge work internally inside the host?

I am trying to understand how the bridged docker0 interface works. When docker daemon starts up, it creates a bridged device docker0; When a container starts up, it creates a interface vthn and bind to docker0 say we issue a ping command from inside the container to a external host [root@f505f022eb5b app]# ping PING […]

How can I forward traffic from a specific port to another in open-vswitch

I am trying to setup an ovs as a transit switch. This would be used to create a data network for a docker container. i.e. In the diagram below, I was able to add veth0-veth3 and veth100 to veth103 to the ovs. but I want to configure such that all traffic from veth0 goes to […]

Docker bridge not showing – is it optional or incorrectly configured?

I’ve got a bridge named docker0. e.g. brctl show bridge name bridge id STP enabled interfaces docker0 8000.0242d342ede7 no vethfb31a5f however if I run docker inspect net2 (where net2 is the name of my container) I get “NetworkSettings”: { “Bridge”: “”, i.e. an empty bridge name. From within the container I can ping the internet […]

Service ports not visible in overlay network across hosts using docker swarm mode

I am using Docker swarm mode in dover 1.12.3 release version in Ubuntu 14.04. Created an overlay network in swarm master and started 3 services say “dse”, “studio”, “opscenter” all to run in a single node in the swarm through node constraints. There are port EXPOSED (not Published) in “dse” say, 9042. As per docker […]

Docker Swarm in Multi VLAN/Subnet Application Stack

I am investigating the feasibility of docker swarm. Our Application stack, which has many apps dockerized, and has multiple VLANs with different subnets in SoftLayer ie Front Facing VLAN (Front end apps only, like CMS and is only vlan that is public internet facing) APP VLAN (all internal only apps) Data VLAN (DBs) Load Balancing […]

How to connect to container which is behind iptables rule

It is common to access a container from out of host with simple iptable rules which forward a port on host to a port on container with container internal IP in hand -A PREROUTING -d -i eth0 -p tcp -m tcp –dport 80 -j DNAT –to-destination So public IP will routed to […]

Docker swarm, listening in container but not outside

We have a number docker images running in a swarm-mode and are having trouble getting one of them to listen externally. If I exec to container I can curl the URL on When I look at networking on the host I see 1 packet being stuck in Recv-Q for this listening port (but not […]

No space left for new subnet when Docker network get address from Flannel

I’m config my Docker with Flannel, it works perfect with default network “docker0″, but when I was trying to create an customized network with command: docker network create my_network It returns: Error response from daemon: failed to parse pool request for address space “GlobalDefault” pool “” subpool “”: cannot find address space GlobalDefault (most likely […]

Windows Containers : Unable to ping containers created with transparent network from other hosts

Environment : Windows Server 2016 in Azure Docker Version : 1.12.2-cs2-ws-beta Kernel Version: 10.0 14393 (14393.321.amd64fre.rs1_release_inmarket.161004-2338) I have created a transparent network with docker network create -d transparent trans and created two containers say A and B in the same network. I am able to ping A from B and vice versa. But i am […]

From docker container to run ping command, regardless of ip addr, always successful

I use docker container to check if there is any others host online. I set docker container –net=host,When I ping any ip address,the response is success, even for those IP address which I have confirmed the host should be down。 The ipaddress range is ip in classs B How do i make it happen?

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