In this article, we will learn how to automatically configure an IP address for ULA.
When to use a unique local address
Unique local addresses (ULA) use the fd00::/8 address block, which is similar to our usual IPv4 private addresses: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. But they are not directly replaceable. IPv4's private address classification and Network Address Translation (NAT) feature is designed to alleviate the shortage of IPv4 addresses. This is a sensible solution that delays the lifecycle of IPv4 that should be replaced. IPv6 also supports NAT, but I can't think of the reason for using it. The number of IPv6 addresses is much larger than IPv4; it is not the same, so you need to do something different.
So what is the meaning of ULA? Especially when we already have the link-local addresses (fe80::/10), do we need to configure them? There are two important differences between them (LCTT: refers to a unique local address and a link-local address). First, the link-local address is not routable, so you can't use it across subnets. Second, the ULA is managed by you; you can choose it for the address range of the subnet and they are routable.
Another benefit of using ULA is that you don't need to assign global unicast IPv6 addresses to them if you're just "mixed" on the LAN. Of course, if your ISP has assigned you IPv6 global unicast addresses, you don't need to use ULA. You can also mix global unicast addresses and ULAs on the same network, but I can't think of a good reason to use them, and make sure you don't use Network Address Translation (NAT) to make ULA publicly accessible. In my opinion, this is a very stupid act.
ULA is used only for private networks and should be prevented from flowing out of your network and not allowed to enter the Internet. This is as simple as blocking the entire fd00::/8 range of IPv6 addresses on your border device.
Automatic address configuration
ULA is not automatically configured like a local link address, but it is very easy to set up automatic configuration using radvd, which is the router advertisement daemon. Before you start, run ifconfig or ip addr show to see your existing IP address.
When using it on a production system, you should install radvd on a separate router. If it's just for testing, you can install it on any Linux PC in your network. In my small KVM test lab, I installed it on Ubuntu using the apt-get install radvd command. After the installation is complete, I won't start it because it doesn't have a configuration file yet:
$sudo systemctl status radvd
â—radvd.service - LSB: Router Advertising Daemon
Loaded: loaded(/etc/init.d/radvd;bad;vendor preset: enabled)
Active: active(exited)since Mon2017-12-1120:08:25PST;4min59sago
Docs: man:systemd-sysv-generator(8)
Dec1120:08:25ubunut1 systemd[1]: Starting LSB: Router Advertising Daemon...
Dec1120:08:25ubunut1 radvd[3541]: Starting radvd:
Dec1120:08:25ubunut1 radvd[3541]: * /etc/radvd.conf does notexist orisempty.
Dec1120:08:25ubunut1 radvd[3541]: * See /usr/share/doc/radvd/README.Debian
Dec1120:08:25ubunut1 radvd[3541]: * radvd will *not* be started.
Dec1120:08:25ubunut1 systemd[1]: Started LSB: Router Advertising Daemon.
All of these messages are a bit confusing. In fact, radvd is not running. You can verify this with the classic command ps | grep radvd. Therefore, we now need to create the /etc/radvd.conf file. Copy this example and replace the first line of the network interface name with your own interface name:
Interfaceens7{
AdvSendAdvert on;
MinRtrAdvInterval3;
MaxRtrAdvInterval10;
Prefix fd7d:844d:3e17:f3ae::/64
{
AdvOnLink on;
AdvAutonomous on;
};
};
The prefix defines your network address, which is the first 64 bits of the address. The first two characters must be fd, the rest of the prefix is ​​left to define itself, and the last 64 bits are left blank, because radvd will allocate the last 64 bits. The 16 bits following the prefix are used to define the subnet, and the remaining addresses are defined as the host address. Your subnet must always be /64. RFC 4193 requires addresses to be randomly generated; see Testing IPv6 Networking in KVM: Part 1 Learn more about creating and managing ULAs.
IPv6 forwarding
IPv6 forwarding must be enabled. The following command to enable it, take effect after reboot:
$sudo sysctl -wnet.ipv6.conf.all.forwarding=1
Uncomment or add the following line to the /etc/sysctl.conf file to make it permanent:
Net.ipv6.conf.all.forwarding = 1
Start the radvd daemon:
$sudo systemctl stop radvd
$sudo systemctl start radvd
This example encountered a weird thing in my Ubuntu test system; radvd always stopped, I checked its status without any problems, and I needed to restart radvd after making any changes.
There is no output after the startup is successful, and the failure is also true, so you need to run sudo systemctl status radvd to check its running status. If there is an error, systemctl will tell you. Commonly common errors are syntax errors in /etc/radvd.conf.
After complaining about the above problem on Twitter, I learned a cool trick: when you run journalctl -xe --no-pager to debug systemctl errors, your output will be wrapped, and then you can see Error message.
Now check your hosts to see the new addresses they are automatically assigned:
$ifconfig
Ens7 Link encap: Ethernet HWaddr52: 54:00:57:71:50
[...]
Inet6 addr: fd7d:844d:3e17:f3ae:9808:98d5:bea9:14d9/64Scope:Global
[...]
The electrolyte material inside the electrolytic capacitor, which has charge storage, is divided into positive and negative polarity, similar to the battery, and cannot be connected backwards.A metal substrate having an oxide film attached to a positive electrode and a negative electrode connected to an electrolyte (solid and non-solid) through a metal plate.
Nonpolar (dual polarity) electrolytic capacitor adopts double oxide film structure, similar to the two polar electrolytic capacitor after two connected to the cathode, the two electrodes of two metal plates respectively (both with oxide film), two groups of oxide film as the electrolyte in the middle.Polar electrolytic capacitors usually play the role of power filter, decoupling (like u), signal coupling, time constant setting and dc isolation in power circuit, medium frequency and low frequency circuit.Non-polar electrolytic capacitors are usually used in audio frequency divider circuit, television S correction circuit and starting circuit of single-phase motor.
Electrolytic Capacitor,Aluminum Electrolytic Capacitor,High Voltage Electrolytic Capacitor,12V Electronic Components Capacitor
YANGZHOU POSITIONING TECH CO., LTD , https://www.yzpstcc.com