mirror of
https://github.com/kernelkit/infix.git
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Joachim Wiberg
e634e945e9
Many of the example prompts used in the documentation are very long and do not fit in generated documentation (web/pdf). This is a proposal to shorten them, sometimes significantly, by keeping only the start and end of an xpath, replacing everything in between with '/…/'. This is a feature that also could be added to the klish-plugin-sysrepo to improve usability. Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
173 lines
6.0 KiB
Markdown
173 lines
6.0 KiB
Markdown
DHCP Server
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===========
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The DHCPv4 server provides automatic IP address assignment and network
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configuration for clients. It supports address pools, static host
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assignments, and customizable DHCP options. It also serves as a DNS
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proxy for local subnets and can even forward queries to upstream DNS
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servers[^1].
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> [!NOTE]
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> When using the CLI, the system automatically enables essential options
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> like DNS servers and default gateway based on the system's network
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> configuration. These options can be disabled, changed or overridden,
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> at any level: global, subnet, or per-host.
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## Basic Configuration
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The following example configures a DHCP server for subnet 192.168.2.0/24
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with an address pool:
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```
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admin@example:/> configure
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admin@example:/config/> edit dhcp-server subnet 192.168.2.0/24
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admin@example:/config/dhcp-server/…/192.168.2.0/24/> set pool start-address 192.168.2.100 end-address 192.168.2.200
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admin@example:/config/dhcp-server/…/192.168.2.0/24/> leave
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```
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When setting up the server from the CLI, the system automatically adds a
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few default DHCP options that will be sent to clients: both DNS server
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and default gateway will use the system address on the matching
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interface.
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```
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admin@example:/> show running-config
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"infix-dhcp-server:dhcp-server": {
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"subnet": [
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{
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"subnet": "192.168.2.0/24",
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"option": [
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{
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"id": "dns-server",
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"address": "auto"
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},
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{
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"id": "router",
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"address": "auto"
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}
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],
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"pool": {
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"start-address": "192.168.2.100",
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"end-address": "192.168.2.200"
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}
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}
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]
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}
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```
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> [!IMPORTANT]
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> Remember to set up an interface in this subnet, avoid using addresses
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> in the DHCP pool, or reserved for static hosts. In Class C networks
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> the router usually has address `.1`. Depending on the use-case, you
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> may also want to set up routing.
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## Static Host Assignment
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To reserve specific IP addresses for clients based on their MAC address,
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hostname, or client ID:
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```
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admin@example:/config/dhcp-server/…/192.168.2.0/24/> edit host 192.168.2.10
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admin@example:/config/dhcp-server/…/192.168.2.10/> set match mac-address 00:11:22:33:44:55
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admin@example:/config/dhcp-server/…/192.168.2.10/> set hostname printer
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admin@example:/config/dhcp-server/…/192.168.2.10/> leave
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```
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Match hosts using a client identifier instead of MAC address:
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```
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admin@example:/config/dhcp-server/…/192.168.1.0/24/> edit host 192.168.1.50
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admin@example:/config/dhcp-server/…/192.168.1.50/> edit match
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admin@example:/config/dhcp-server/…/match/> set client-id hex c0:ff:ee
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admin@example:/config/dhcp-server/…/match/> leave
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admin@example:/config/dhcp-server/…/192.168.1.50/> set lease-time infinite
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admin@example:/config/dhcp-server/…/192.168.1.50/> leave
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```
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The `hex` prefix here ensures matching of client ID is done using the
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hexadecimal octets `c0:ff:ee`, three bytes. Without the prefix the
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ASCII string "c0:ff:ee", eight bytes, is used.
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> [!NOTE]
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> The DHCP server is fully RFC conformant, in the case of option 61 this
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> means that using the `hex` prefix will require the client to set the
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> `htype` field of the option to `00`. See RFC 2132 for details.
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## Custom DHCP Options
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Configure additional DHCP options globally, per subnet, or per host:
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```
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admin@example:/config/dhcp-server/> edit subnet 192.168.2.0/24
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admin@example:/config/dhcp-server/subnet/192.168.2.0/24/> edit option dns-server
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admin@example:/config/dhcp-server/subnet/192.168.2.0/24/option/dns-server/> set address 8.8.8.8
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admin@example:/config/dhcp-server/subnet/192.168.2.0/24/option/dns-server/> leave
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admin@example:/config/dhcp-server/subnet/192.168.2.0/24/> edit option ntp-server
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admin@example:/config/dhcp-server/subnet/192.168.2.0/24/option/ntp-server/> set address 192.168.2.1
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admin@example:/config/dhcp-server/subnet/192.168.2.0/24/option/ntp-server/> leave
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```
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When configuring, e.g., `dns-server`, or `router` options with the value
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`auto`, the system uses the IP address from the interface matching the
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subnet. For example:
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```
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admin@example:/> show interfaces
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INTERFACE PROTOCOL STATE DATA
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eth0 ethernet UP 02:00:00:00:00:00
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ipv4 192.168.1.1/24 (static)
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eth1 ethernet UP 02:00:00:00:00:01
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ipv4 192.168.2.1/24 (static)
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admin@example:/config/dhcp-server/subnet/192.168.1.0/24/> edit option dns-server
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admin@example:/config/dhcp-server/subnet/192.168.1.0/24/option/dns-server/> set address auto
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admin@example:/config/dhcp-server/subnet/192.168.1.0/24/option/dns-server/> leave
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```
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In this case, clients in subnet 192.168.1.0/24 will receive 192.168.1.1
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as their DNS server address.
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## Multiple Subnets
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Configure DHCP for multiple networks:
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```
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admin@example:/> configure
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admin@example:/config/> edit dhcp-server
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admin@example:/config/dhcp-server/> edit subnet 192.168.1.0/24
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admin@example:/config/dhcp-server/subnet/192.168.1.0/24/> set pool start-address 192.168.1.100 end-address 192.168.1.200
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admin@example:/config/dhcp-server/subnet/192.168.1.0/24/> leave
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admin@example:/config/dhcp-server/> edit subnet 192.168.2.0/24
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admin@example:/config/dhcp-server/subnet/192.168.2.0/24/> set pool start-address 192.168.2.100 end-address 192.168.2.200
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admin@example:/config/dhcp-server/subnet/192.168.2.0/24/> leave
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```
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## Monitoring
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View active leases and server statistics:
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```
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admin@example:/> show dhcp-server
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IP ADDRESS MAC HOSTNAME CLIENT ID EXPIRES
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192.168.2.22 00:a0:85:00:02:05 00:c0:ff:ee 3591s
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192.168.1.11 00:a0:85:00:04:06 foo 01:00:a0:85:00:04:06 3591s
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admin@example:/> show dhcp-server statistics
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DHCP offers sent : 6
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DHCP ACK messages sent : 5
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DHCP NAK messages sent : 0
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DHCP decline messages received : 0
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DHCP discover messages received : 6
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DHCP request messages received : 5
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DHCP release messages received : 6
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DHCP inform messages received : 6
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```
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[^1]: This requires the system DNS resolver to be configured.
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