Introduction to Linux Network Namespaces

Summary

This video introduces Linux network namespaces, demonstrating their application through two practical examples. First, it shows how to emulate a network topology similar to Mininet using network namespaces, Open vSwitch, and virtual Ethernet pairs for host isolation. Next, it mimics OpenStack's DHCP services by using network namespaces to simulate tenant isolation in a cloud environment. The video covers setting up interfaces, assigning IP addresses, and running isolated DHCP processes for different tenants. By the end, viewers learn how network namespaces provide network isolation, enabling flexible, isolated environments for virtualized networking and cloud infrastructure.

Takeaways

• 😀 Network namespaces allow for isolated network environments on a single physical or virtual host.
• 😀 Network namespaces are used in various technologies like OpenStack, Docker, Linux containers, and Mininet.
• 😀 Mininet emulates virtual network topologies within a single VM or host, and network namespaces help isolate the environments of different hosts.
• 😀 Open vSwitch (OVS) can be used to create virtual switches, enabling communication between network namespaces in Linux.
• 😀 Virtual Ethernet pairs (V pairs) are used to connect network namespaces and virtual switches, creating isolated network connections.
• 😀 A practical example demonstrated how two network namespaces (red and green) can be created and connected using OVS and V pairs.
• 😀 Each network namespace operates independently, with its own routing and IP addressing, making it suitable for isolation in multi-tenant environments.
• 😀 The root namespace in Linux is the default network environment, but new namespaces can be created for isolated network setups.
• 😀 OpenStack's DHCP service to tenants can be simulated using network namespaces, allowing for isolated DHCP processes for each tenant.
• 😀 VLAN tagging on OVS ports helps separate traffic between different network namespaces, ensuring network isolation in multi-tenant scenarios.

Q & A

What are Linux Network namespaces?

Linux Network namespaces allow multiple isolated network environments to run on a single physical host or virtual machine. Each namespace has its own interfaces, routing tables, and network security, and processes can be dedicated to an individual namespace to isolate them from others.

How are network namespaces used in practical scenarios?

Network namespaces are used in various applications such as OpenStack, Linux containers, Docker, Mininet, and more, where they help to isolate different network environments for processes and services.

What is Mininet, and how is it used in the video?

Mininet is a software that allows the creation of custom virtual network topologies within a single physical or virtual machine. In the video, Mininet is mimicked manually using network namespaces to emulate a simple network topology with two hosts connected by a virtual switch.

How are virtual Ethernet pairs (V pairs) used in the network setup?

Virtual Ethernet pairs (V pairs) are used to connect different network namespaces. One end of the pair is placed in one namespace (e.g., red), while the other is attached to a virtual switch or another namespace (e.g., green).

What role does Open vSwitch (OVS) play in the network setup?

Open vSwitch (OVS) is used as a virtual switch to connect the network namespaces. It enables layer 2 connectivity between the red and green namespaces through virtual Ethernet pairs, mimicking the behavior of a physical switch.

How are IP addresses assigned to network namespaces?

IP addresses are assigned within each network namespace using the 'ip netns exec' command. After setting up interfaces and bringing them up, IP addresses are manually assigned to interfaces within the namespaces using commands like 'ip address add'.

What is the purpose of VLANs in the second example of OpenStack DHCP?

VLANs are used in the second example to isolate the two network namespaces (red and green), which represent different tenants in a cloud environment. VLANs ensure that the tenants' network traffic remains separated, even though both namespaces are connected to the same Open vSwitch instance.

How does DHCP work in the context of network namespaces?

In the video, DHCP is simulated by running DNSMasq services within separate network namespaces. Each namespace has its own isolated DHCP process, which assigns IP addresses to its respective interfaces using specific address ranges.

How are DNSMasq services isolated between tenants?

DNSMasq services are isolated by running them in separate network namespaces, ensuring that each tenant has its own isolated DHCP service. The services use different namespaces, so they do not interfere with each other, even though they might have overlapping IP address ranges.

What is the final outcome of the video example with Open vSwitch and DHCP?

The final outcome demonstrates two isolated network namespaces (red and green) connected via Open vSwitch, with each namespace running a separate DHCP process. The namespaces are isolated from each other, and each tenant successfully receives an IP address from its respective DNSMasq service.