没有任何问题ppp。运行并更新，它停止工作。
我的设置：
Lenovo T470s with Fedora 28, Linux user-fedora 4.18.13-200.fc28.x86_64 #1 SMP Wed Oct 10 17:29:59 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
custom board with Linux custom-board-0 4.14.0-xilinx-v2018.2 #1 SMP PREEMPT Mon Sep 24 12:55:51 PDT 2018 armv7l armv7l armv7l GNU/Linux
ppp在 Fedora 28 上运行的命令
sudo pppd -detach local debug noauth passive xonxoff lock dump 192.168.10.100:192.168.10.1 /dev/ttyUSB0 9600`
ppp在自定义板上运行的命令
pppd -detach persist debug local noauth passive xonxoff lock dump 192.168.10.1:192.168.10.100 /dev/ttyS0 9600
ppp命令执行后 Fedora 上的输出
pppd options in effect:
debug # (from command line)
-detach # (from command line)
dump # (from command line)
noauth # (from command line)
/dev/ttyUSB0 # (from command line)
9600 # (from command line)
lock # (from command line)
xonxoff # (from command line)
local # (from command line)
passive # (from command line)
192.168.10.100:192.168.10.1 # (from command line)
using channel 16
Using interface ppp0
Connect: ppp0 <--> /dev/ttyUSB0
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
LCP: timeout sending Config-Requests
ppp命令执行后自定义板上的输出
pppd options in effect:
debug # (from command line)
-detach # (from command line)
persist # (from command line)
dump # (from command line)
noauth # (from command line)
/dev/ttyS0 # (from command line)
9600 # (from command line)
lock # (from command line)
xonxoff # (from command line)
local # (from command line)
passive # (from command line)
192.168.10.1:192.168.10.100 # (from command line)
using channel 11
Using interface ppp0
Connect: ppp0 <--> /dev/ttyS0
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x4b51417a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
LCP: timeout sending Config-Requests
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0xa0000> <magic 0x1aa6d871> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <asyncmap 0xa0000> <magic 0x82da991a> <pcomp> <accomp>]
LCP: timeout sending Config-Requests
看起来 Fedora 正在发送 LCP 数据包，而 Custom Board 正在接收它们，而 Custom Board 正在发送 LCP 数据包，但 Fedora 没有接收它们。
有谁知道可能是什么问题以及如何解决它？
答案1
经过一天的调试，发现是定制板的问题。结果发现连接器中的一根插针已被电气损坏。所以这不是 Fedora 或 PPP 的问题，而是硬件连接器的问题。感谢大家的关注。