㈠ centos7隻能ping通自己的ip，同一網段的IP主機直連都無法ping通
如果能ping通自己，。那麼自己硬體和協議都沒問題，對方沒做任何限制的話，那就是線不對了。
這里只考慮直接一層連接，沒那些彎彎繞的情況。
㈡ CentOS7網路設置修復
伺服器有兩個網卡enp7s0和enp8s0
伺服器需要通過enp8s0和互聯網聯通，互聯網為筆記本轉接
通過centos7界面修改ip，失敗；
通過centos7的網路配置文件/etc/sysconfig/network-scripts/ifcfg-enp8s0修改ip設置
設置如下：
1.啟動 service network start 報錯，通過journalctl -xe查看如下
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit fprintd.service has begun starting up.
12月 29 19:31:12 crrchost dbus-daemon[851]: dbus[851]: [system] Successfully activated service 'net.reactivated.Fprint'
12月 29 19:31:12 crrchost dbus[851]: [system] Successfully activated service 'net.reactivated.Fprint'
12月 29 19:31:12 crrchost systemd[1]: Started Fingerprint Authentication Daemon.
-- Subject: Unit fprintd.service has finished start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit fprintd.service has finished starting up.
--
-- The start-up result is done.
12月 29 19:31:12 crrchost fprintd[6685]: Launching FprintObject
12月 29 19:31:12 crrchost fprintd[6685]: ** Message: D-Bus service launched with name: net.reactivated.Fprint
12月 29 19:31:12 crrchost fprintd[6685]: ** Message: entering main loop
12月 29 19:31:18 crrchost polkitd[835]: Operator of unix-session:1 successfully authenticated as unix-user:windfarm to gain TEMPORARY authorization for action org.freedesktop.systemd1.manage-units for system-bus
12月 29 19:31:18 crrchost systemd[1]: Starting LSB: Bring up/down networking...
-- Subject: Unit network.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit network.service has begun starting up.
12月 29 19:31:18 crrchost network[6693]: 正在打開環回介面： [ 確定 ]
12月 29 19:31:18 crrchost network[6693]: 正在打開介面 enp7s0：
12月 29 19:31:24 crrchost network[6693]: 正在確定 enp7s0 的 IP 信息...失敗：不存在鏈接。檢查電纜？
12月 29 19:31:24 crrchost network[6693]: [失敗]
12月 29 19:31:24 crrchost network[6693]: 正在打開介面 enp8s0： RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: [ 確定 ]
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost network[6693]: RTNETLINK answers: File exists
12月 29 19:31:25 crrchost systemd[1]: network.service: control process exited, code=exited status=1
12月 29 19:31:25 crrchost systemd[1]: Failed to start LSB: Bring up/down networking.
-- Subject: Unit network.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit network.service has failed.
--
-- The result is failed.
12月 29 19:31:25 crrchost systemd[1]: Unit network.service entered failed state.
12月 29 19:31:25 crrchost systemd[1]: network.service failed.
12月 29 19:31:25 crrchost polkitd[835]: Unregistered Authentication Agent for unix-process:6669:319312 (system bus name :1.263, object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale zh_CN.UTF-8) (d
3.systemctl status network.service查看如下：
● network.service - LSB: Bring up/down networking
Loaded: loaded (/etc/rc.d/init.d/network; bad; vendor preset: disabled)
Active: failed (Result: exit-code) since 六 2018-12-29 18:38:17 CST; 1min 24s ago
Docs: man:systemd-sysv-generator(8)
Process: 909 ExecStart=/etc/rc.d/init.d/network start (code=exited, status=1/FAILURE)
12月 29 18:38:06 crrchost systemd[1]: Starting LSB: Bring up/down networking...
12月 29 18:38:06 crrchost network[909]: 正在打開環回介面： [ 確定 ]
12月 29 18:38:06 crrchost network[909]: 正在打開介面 enp7s0：
12月 29 18:38:12 crrchost network[909]: 正在確定 enp7s0 的 IP 信息...失敗：…？
12月 29 18:38:12 crrchost network[909]: [失敗]
12月 29 18:38:17 crrchost network[909]: 正在打開介面 enp8s0： [ 確定 ]
12月 29 18:38:17 crrchost systemd[1]: network.service: control process exi...=1
12月 29 18:38:17 crrchost systemd[1]: Failed to start LSB: Bring up/down n...g.
12月 29 18:38:17 crrchost systemd[1]: Unit network.service entered failed ...e.
12月 29 18:38:17 crrchost systemd[1]: network.service failed.
Hint: Some lines were ellipsized, use -l to show in full.
1.參考網路方法停用NetworkManager，依舊報錯
systemctl stop NetworkManager
systemctl disable NetworkManager
2.比對兩個網卡的MAC地址和配置文件的MAC地址
a.查看mac地址配置，ipconfig
b.查看配置文件中的macd地址是否匹配，ifcfg-enp8s0和ifcfg-enp7s0,
按照網路方法增加一行HWADDR=ipconfig查詢到的對應網卡MAC地址；
c.重啟network服務依舊報錯；
3.通過GUI界面查看網路，提示「系統的網路服務與此版本的網路管理器不兼容」
這與之前停掉NetworkManager有關，此處不表；
4.因為ifcfg-enp7s0實際上沒有插網線，修正其配置文件如下：
ONBOOT=no
重新啟動服務後網路正常；
5.檢查網路
1.network 和NetworkManager不同，通過界面和通過配置文件，可能會導致配置混亂，且NetworkManager有些程序不支持，需要停用；
2.BOOTPROTO=none 雖然可以表示靜態ip，但是如果要啟用，必須設置其為
BOOTPROTO=static 或BOOTPROTO=dhcp
3.一個網卡沒喲被啟用，也就是沒有設置動態ip或靜態ip，是無法被初始化的，不能設置ONBOOT=yes
In Centos7.0 disabling NetworkManager will leave a dhcp client running configured for NetworkManager. This causes the error message RTNETLINK answers: File exists when the network service is started.
The stale dhclient process has the additional "benefit" that when the lease expires your dhclientwill choke, since it cannot reach NetWorkManager, thus removing your IP address.
If you grep for it, you will see that it points to a NetWorkManager configuration file.
[root@host ~]# ps -ef | grep dhc
root 1865 792 0 Apr28 ? 00:00:00 /sbin/dhclient -d -sf \
/usr/libexec/nm-dhcp-helper -pf /var/run/dhclient-eno1.pid -lf\
/var/lib/NetworkManager/dhclient-c96e56d3-a4c9-4a87-85ca-93dc0ca268f2-eno1.lease\
-cf /var/lib/NetworkManager/dhclient-eno1.conf eno1
So what you can do is kill the dhclient and only then start your network service.