DHCP协议
- 动态主机设置协议，使用UDP协议工作
- 用途
- 服务器端使用67/udp，客户端使用68/udp
- 基本过程
- 请求IP租约（discover）
- 提供IP租约（offer）
- 选择IP租约（request）
- 确认IP租约（ack）
- 获得IP地址后，发送ARP请求来避免地址池重叠而引发的IP重复冲突
# udhcpc --help
BusyBox v1.20.2 (2019-11-18 19:40:16 PST) multi-call binary.
Usage: udhcpc [-fbnqvoCRB] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]
[-V VENDOR] [-x OPT:VAL]... [-O OPT]...
-i,--interface IFACE Interface to use (default eth0)
-p,--pidfile FILE Create pidfile
-s,--script PROG Run PROG at DHCP events (default /usr/share/udhcpc/default.script)
-B,--broadcast Request broadcast replies
-t,--retries N Send up to N discover packets
-T,--timeout N Pause between packets (default 3 seconds)
-A,--tryagain N Wait N seconds after failure (default 20)
-f,--foreground Run in foreground
-b,--background Background if lease is not obtained
-n,--now Exit if lease is not obtained
-q,--quit Exit after obtaining lease
-R,--release Release IP on exit
-S,--syslog Log to syslog too
-a,--arping Use arping to validate offered address
-O,--request-option OPT Request option OPT from server (cumulative)
-o,--no-default-options Don't request any options (unless -O is given)
-r,--request IP Request this IP address
-x OPT:VAL Include option OPT in sent packets (cumulative)
Examples of string, numeric, and hex byte opts:
-x hostname:bbox - option 12
-x lease:3600 - option 51 (lease time)
-x 0x3d:0100BEEFC0FFEE - option 61 (client id)
-F,--fqdn NAME Ask server to update DNS mapping for NAME
-V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')
-C,--clientid-none Don't send MAC as client identifier
-v Verbose
Signals:
USR1 Renew lease
USR2 Release lease
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