To create and use a network namespace, you need to create it first, then assign the interface and IP, and set up the routing to achieve communication. The steps are as follows: 1. Create a namespace with ip netns add; 2. Create a veth pair through ip link add and move one end into the namespace; 3. Assign IP to the interface and enable it; 4. If you need external network access, enable IP forwarding, configure iptables MASQUERADE and set default routes; 5. Close the interface first and clean the rules when deleting. The entire process needs to pay attention to resource cleaning and rule consistency.
Network Namespace is a mechanism provided by Linux to isolate network environments, and is often used in container technology, virtualization and network debugging. If you want to create a separate network environment in your system, such as testing different configurations or running multiple service instances without conflict, network namespace is very useful.
Here are some usage and precautions that you may be concerned about.
Create and enter a network namespace
To use network namespace, you need to create it first. The simplest command is:
ip netns add ns1
This creates a network namespace called ns1 . You can view all current network namespaces through the following command:
ip netns list
To execute commands in this namespace, you can use ip netns exec , for example:
ip netns exec ns1 ip addr
This way you can see the network interface information in the namespace.
Assign IP and network interfaces to namespaces
The namespace I just created has only one loopback interface by default, and you need to manually add a network card to make it connected to the network. It is usually done by creating a pair of virtual Ethernet devices and putting one into the namespace.
The operation steps are as follows:
Create a veth pair:
ip link add veth0 type veth peer name veth1
Put one end into the namespace:
ip link set veth1 netns ns1
Assign IPs to both ends separately and enable:
ip addr add 192.168.1.1/24 dev veth0 ip link set veth0 up ip netns exec ns1 ip addr add 192.168.1.2/24 dev veth1 ip netns exec ns1 ip link set veth1 up ip netns exec ns1 ip link set lo up
In this way, the two network interfaces can communicate with each other.
Implement namespace access to the external network
If you want the namespace to have access to external networks, you also need to do NAT forwarding and routing settings.
Key steps include:
Turn on the host's IP forwarding:
echo 1 > /proc/sys/net/ipv4/ip_forward
Setting iptables MASQUERADE rules:
iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -o eth0 -j MASQUERADE
Set the default route in the namespace:
ip netns exec ns1 ip route add default via 192.168.1.1
After doing this, the namespace can access the Internet like a normal machine.
Delete namespaces and clean resources
When you no longer need a namespace, you can delete it with the following command:
ip netns delete ns1
But note: If there are still network interfaces bound to the namespace, deletion will fail. It is recommended to close the relevant interface first and then delete it.
In addition, if you set iptables rules before, remember to manually clear them to avoid leaving useless rules to affect subsequent network behavior.
Basically that's it. By mastering these key points, you can start using network namespace to build your own isolated network environment. Although it seems a bit complicated, every step is not difficult. The key is to understand the relationship between interfaces and routes.
The above is the detailed content of How to use network namespaces. For more information, please follow other related articles on the PHP Chinese website!
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