Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Tutorial on using CoreOS Flannel for Docker networking

19,707 views

Published on

Flannel is an overlay based networking technique for networking Docker containers on CoreOS platforms. This tutorial explains the theory, setup instructions and limtations of the mechanism.

Published in: Technology

Tutorial on using CoreOS Flannel for Docker networking

  1. 1. Docker Networking Tutorial – CoreOS Flannel Srini Seetharaman srini@sdnhub.org November, 2014
  2. 2. CoreOS Flannel
  3. 3. • Lightweight OS based on Gentoo Linux • Has a distributed key-value store at the core • Read-only rootfs. Writeable /etc o All services are in containers CoreOS
  4. 4. • One CIDR subnet per machine, like Kubernetes o Host 1: 10.10.10.0/24 o Host 2: 10.10.11.0/24 • No Docker port-based mapping • Containers reach each other through IP • Peer network configs exchanged over etcd • Packets encapsulated using UDP, and soon VxLAN Flannel Basic 4
  5. 5. 1. Build flannel on each host 2. Set key in etcd for network config Instructions to Run Flannel 6 $ curl -L http://127.0.0.1:4001/v2/keys/coreos.com/network/config -XPUT -d value='{ "Network": "10.0.0.0/8", "SubnetLen": 20, "SubnetMin": "10.10.0.0", "SubnetMax": "10.99.0.0", "Backend": {"Type": "udp", "Port": 7890}} $ git clone https://github.com/coreos/flannel.git $ cd flannel $ docker run -v `pwd`:/opt/flannel -i -t google/golang /bin/bash -c "cd /opt/flannel && ./build"
  6. 6. 3. Start flannel. o flanneld port created and route is set for the full flat IP range. Instructions to Run Flannel (contd.) 7 $ sudo ./bin/flanneld & Output: I1219 17:34:41.159822 00809 main.go:247] Installing signal handlers I1219 17:34:41.160030 00809 main.go:118] Determining IP address of default interface I1219 17:34:41.160579 00809 main.go:205] Using 192.168.111.14 as external interface I1219 17:34:41.212157 00809 subnet.go:83] Subnet lease acquired: 10.12.224.0/20 I1219 17:34:41.217829 00809 main.go:215] UDP mode initialized I1219 17:34:41.218953 00809 udp.go:239] Watching for new subnet leases I1219 17:34:41.219349 00809 udp.go:264] Subnet added: 10.13.128.0/20 core@coreos-05 ~ $ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.111.1 0.0.0.0 UG 1024 0 0 eth0 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 flannel0 10.12.224.0 0.0.0.0 255.255.240.0 U 0 0 0 docker0 192.168.111.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
  7. 7. 4. Restart docker daemon with appropriate bridge IP Instructions to Run Flannel (contd.) 8 $ source /run/flannel/subnet.env $ sudo ifconfig docker0 ${FLANNEL_SUBNET} $ sudo docker -d --bip=${FLANNEL_SUBNET} --mtu=${FLANNEL_MTU} &
  8. 8. • Ping between two bash containers on two different hosts succeeds. The traffic on wire is encapsulated by flanneld Testing Flannel Networking 9 192.168.111.14 Docker0 10.12.224.1 bash 192.168.111.13 Docker0 10.13.128.1 bash $ docker run -i -t ubuntu /bin/bash root@36484def3b03:/# ifconfig eth0 eth0 Link encap:Ethernet HWaddr 02:42:0a:0c:e0:02 inet addr:10.12.224.2 Bcast:0.0.0.0 Mask:255.255.240.0 root@36484def3b03:/# ping 10.13.128.2 Success! $ docker run -i -t ubuntu /bin/bash root@e0b9dd20d146:/# ifconfig eth0 eth0 Link encap:Ethernet HWaddr 02:42:0a:0d:80:02 inet addr:10.13.128.2 Bcast:0.0.0.0 Mask:255.255.240.0
  9. 9. Packet on the Wire 10 Original ICMP packet between the two containers Flannel introduced encap UDP header
  10. 10. • IP address overlap not possible o VxLAN not used to create container groups • User-space encapsulation and forwarding o Potential performance bottleneck Limitations 11
  11. 11. Thank you. https://github.com/sdnhub/lorispack © 2015 Copyright Reserved

×