46.第十章 网络协议和管理配置(七)

wuchangjian2021-11-16 17:05:15编程学习

3.5.7 划分子网

划分子网:将一个大的网络(主机数多)划分成多个小的网络(主机数少),主机ID位数变少,网络ID位数变多,网络ID位向主机ID位借位

划分子网的数量由网络ID向主机ID借的位决定

子网数量=2^网络ID向主机ID借位
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可变长度子网掩码
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Subnet地址
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范例:

10.0.0.0/8

2^24-2

172.16.0.0/16

网段数=2^可变的网络ID位
一个网络的最大主机数=2^主机ID的位-2

主机ID位越多,主机数越多,网络越大
主机ID位数变少,主机数量越少,网络越小

划分子网: 

10.00  000000.0.0

10.0 0000000.0.1
10.1 1111111.255.254

10.0 0000000.0.0  10.0.0.0/9  
10.1 0000000.0.0  10.128.0.0/9

10.00000000.0.0 10.0.0.0/10
10.01000000.0.0 10.64.0.0/10
10.10000000.0.0 10.128.0.0/10
10.11000000.0.0 10.192.0.0/10

划分子网的数量由网络ID向主机ID借的位决定
子网数量=2^网络ID向主机ID借位

范例:

中国移动10.0.0.0/8 给32个各省公司划分对应的子网
1)每个省公司的子网的netmask?
2^5>=32 借5位网络ID
8+5=13
255.11111000.0.0
255.248.0.0

2)每个省公司的子网的主机数有多少?
2^(32-13)-2=524286

3)第一个子网的网络ID? 
10.00000 000.0.0
10.0.0.0/13

4)河南省得到第10个子网,网络ID?
10.01001 000.0.0/13
10.72.0.0/13

5)河南省得到第10个子网的最小IP和最大的IP?
10.01001 000.0.1
10.01001 111.11111111.11111110

10.72.0.1---10.79.255.254

6)所有子网中最大,最小的子网的网络ID(NETID)10.00000 000.0.0/13 10.0.0.0/13
10.11111 000.0.0/13 10.248.0.0/13

范例:

中国移动10.0.0.0/8  给32个省公司划分对应的子网,河南省得到第10个子网,再给省内的16个地市划分子网
10.01001 000.0.0 10.72.0.0/13

1)每个市公司的子网的netmask?
2^4>=16  借4位网络ID
13+4=17
255.255.128.0
2)每个市公司的子网的主机数有多少?
32-17=15  2^15-2=32766
3)各地市的最小netid和最大netid?
10.72.0.0-10.79.128.0

4)洛阳市第2个子网,最小IP和最大IP?
10.72.128.1-10.72.255.254

10.01001000.00000000.0/17 10.72.0.1-10.72.127.254
10.01001000.10000000.0/17 10.72.128.1-10.72.255.254 
10.01001001.00000000.0/17 10.73.0.1-10.73.127.254
10.01001001.10000000.0/17 10.73.128.0-10.73.255.254
10.01001010.00000000.0/17 10.74.0.1-10.74.127.254
10.01001010.10000000.0/17 10.74.128.1-10.74.255.254
10.01001011.00000000.0/17 10.75.0.1-10.75.127.254
10.01001011.10000000.0/17 10.75.128.1-10.75.255.254
10.01001100.00000000.0/17 10.76.0.1-10.76.127.254
10.01001100.10000000.0/17 10.76.128.1-10.76.255.254
10.01001101.00000000.0/17 10.77.0.1-10.77.127.254
10.01001101.10000000.0/17 10.77.128.1-10.77.255.254
10.01001110.00000000.0/17 10.78.0.1-10.78.127.254
10.01001110.10000000.0/17 10.78.128.1-10.255.254
10.01001111.00000000.0/17 10.79.0.1-10.79.127.254
10.01001111.10000000.0/17 10.79.128.1-10.79.255.254

3.5.8 优化IP地址分配

在这里插入图片描述
合并超网:将多个小网络合并成一个大网,主机ID位向网络ID位借位,主要实现路由聚合功能

范例:

#2000个主机分配了8个C类网段
220.78.168.0/24
220.78.169.0/24
220.78.170.0/24
220.78.171.0/24
220.78.172.0/24
220.78.173.0/24
220.78.174.0/24
220.78.175.0/24

220.78.10101 000.0 220.78.168.0/24
220.78.10101 001.0 220.78.169.0/24
220.78.10101 010.0 220.78.170.0/24
...
220.78.10101 110.0 220.78.174.0/24
220.78.10101 111.0 220.78.175.0/24

#合并成
220.78.168.0/21

3.5.9 跨网络通信

跨网络通信:路由,选择路径

路由分类:

  • 主机路由
  • 网络路由
  • 默认路由

优先级:精度越高,优先级越高

3.5.10 动态主机配置协议 DHCP

在这里插入图片描述

4.网络配置

4.1 基本网络配置

将Linux主机接入到网络,需要配置网络相关设置

一般包括如下内容:

  • 主机名

  • IP/netmask

  • 路由:默认网关

  • DNS服务器

    主DNS服务器

    次DNS服务器

    第三个DNS服务器

范例:

[root@rocky8 ~]# hostname
rocky8
[root@rocky8 ~]# ping rocky8
PING rocky8(rocky8 (fe80::20c:29ff:fef9:6ad1%eth0)) 56 data bytes
64 bytes from rocky8 (fe80::20c:29ff:fef9:6ad1%eth0): icmp_seq=1 ttl=64 time=0.063 ms
64 bytes from rocky8 (fe80::20c:29ff:fef9:6ad1%eth0): icmp_seq=2 ttl=64 time=0.052 ms
64 bytes from rocky8 (fe80::20c:29ff:fef9:6ad1%eth0): icmp_seq=3 ttl=64 time=0.036 ms
64 bytes from rocky8 (fe80::20c:29ff:fef9:6ad1%eth0): icmp_seq=4 ttl=64 time=0.042 ms
^C
--- rocky8 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3079ms
rtt min/avg/max/mdev = 0.036/0.048/0.063/0.011 ms

4.2 CentOS 6 之前版本网卡名称

接口命名方式:CentOS 6

​ 以太网:eth[0,1,2,…]

​ ppp:ppp[0,1,2,…]

网络接口识别并命名相关的udev配置文件:

​ /etc/udev/rules.d/70-persistent-net.rules

查看网卡:

​ dmesg |grep –i eth

​ ethtool -i eth0

卸载网卡驱动:

​ modprobe -r e1000

​ rmmod e1000

装载网卡驱动:

​ modprobe e1000

范例:临时修改网卡名称

[root@centos6 ~]# ip link set eth0 down
[root@centos6 ~]# ip link set eth0 name abc
[root@centos6 ~]# ip link set abc up

范例:

#克隆一台centos6 主机出来
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在这里插入图片描述

在这里插入图片描述
#ethtool -i eth1 查看网卡驱动为e1000

在这里插入图片描述
#modprobe -r e1000 卸载网卡驱动

在这里插入图片描述
#modprobe e1000 加载网卡驱动

在这里插入图片描述
在这里插入图片描述
#现在没有IP地址

在这里插入图片描述
#ifconfig eth0 172.31.0.66/21,临时修改IP地址

4.3 网络配置命令

4.3.1 网络配置方式

  • 静态指定:

    ifconfig, route, netstat

    ip: object {link, addr, route}, ss, tc

    system-config-network-tui,setup

    配置文件

  • 动态分配:DHCP: Dynamic Host Configuration Protocol

4.3.2 ifconfig命令

来自于net-tools包,建议使用 ip 代替

[root@rocky8 ~]# which ifconfig
/usr/sbin/ifconfig
[root@rocky8 ~]# rpm -qf `which ifconfig`
net-tools-2.0-0.52.20160912git.el8.x86_64
[root@rocky8 ~]# rpm -qi net-tools
Name        : net-tools
Version     : 2.0
Release     : 0.52.20160912git.el8
Architecture: x86_64
Install Date: Mon 25 Oct 2021 05:22:25 PM CST
Group       : System Environment/Base
Size        : 964894
License     : GPLv2+
Signature   : RSA/SHA256, Mon 12 Apr 2021 06:31:49 AM CST, Key ID 15af5dac6d745a60
Source RPM  : net-tools-2.0-0.52.20160912git.el8.src.rpm
Build Date  : Wed 07 Apr 2021 11:41:10 AM CST
Build Host  : ord1-prod-x86build001.svc.aws.rockylinux.org
Relocations : (not relocatable)
Packager    : infrastructure@rockylinux.org
Vendor      : Rocky
URL         : http://sourceforge.net/projects/net-tools/
Summary     : Basic networking tools
Description :
The net-tools package contains basic networking tools,
including ifconfig, netstat, route, and others.
Most of them are obsolete. For replacement check iproute package.

[root@rocky8 ~]# rpm -ql net-tools
/usr/bin/netstat
/usr/lib/.build-id
/usr/lib/.build-id/02
/usr/lib/.build-id/02/9bd2bbada4d981bd08eec1b69c417ec0540464
/usr/lib/.build-id/18
/usr/lib/.build-id/18/e13de699b88ffca36b146a8173afd31ffa4bfa
/usr/lib/.build-id/38
/usr/lib/.build-id/38/d5f513a2c3495d28e4aa0618ced7aa8b091719
/usr/lib/.build-id/3f
/usr/lib/.build-id/3f/7dd7b481bc94f655e33d5c48f82850cde2c2dd
/usr/lib/.build-id/40
/usr/lib/.build-id/40/7e45207270c9a482333d312954a9b57b1a4ef0
/usr/lib/.build-id/4b
/usr/lib/.build-id/4b/eae4ed5cd7e395e1affac0bb264b8060cc3855
/usr/lib/.build-id/88
/usr/lib/.build-id/88/26fdea3b3a6b0fb11618354fe056ee1170c2a1
/usr/lib/.build-id/93
/usr/lib/.build-id/93/66d7a14b144fd1470e4ded9971f70fb81feeba
/usr/lib/.build-id/98
/usr/lib/.build-id/98/655a9c5c9a4728d1c25101a56f3149fa10b329
/usr/lib/.build-id/a5
/usr/lib/.build-id/a5/ef7e9bb55436dc8eb3d2414afd40c1df134640
/usr/lib/.build-id/af
/usr/lib/.build-id/af/dcfd9fa89871631d511adc2fc5affac225d8eb
/usr/lib/.build-id/e4
/usr/lib/.build-id/e4/5566d09948e5656abffefaf0aa81521012e80f
/usr/lib/systemd/system/arp-ethers.service
/usr/sbin/arp
/usr/sbin/ether-wake
/usr/sbin/ifconfig
/usr/sbin/ipmaddr
/usr/sbin/iptunnel
/usr/sbin/mii-diag
/usr/sbin/mii-tool
/usr/sbin/nameif
/usr/sbin/plipconfig
/usr/sbin/route
/usr/sbin/slattach
/usr/share/licenses/net-tools
/usr/share/licenses/net-tools/COPYING
/usr/share/locale/cs/LC_MESSAGES/net-tools.mo
/usr/share/locale/de/LC_MESSAGES/net-tools.mo
/usr/share/locale/et_EE/LC_MESSAGES/net-tools.mo
/usr/share/locale/fr/LC_MESSAGES/net-tools.mo
/usr/share/locale/pt_BR/LC_MESSAGES/net-tools.mo
/usr/share/man/de/man5/ethers.5.gz
/usr/share/man/de/man8/arp.8.gz
/usr/share/man/de/man8/ifconfig.8.gz
/usr/share/man/de/man8/netstat.8.gz
/usr/share/man/de/man8/plipconfig.8.gz
/usr/share/man/de/man8/route.8.gz
/usr/share/man/de/man8/slattach.8.gz
/usr/share/man/fr/man5/ethers.5.gz
/usr/share/man/fr/man8/arp.8.gz
/usr/share/man/fr/man8/ifconfig.8.gz
/usr/share/man/fr/man8/netstat.8.gz
/usr/share/man/fr/man8/plipconfig.8.gz
/usr/share/man/fr/man8/route.8.gz
/usr/share/man/fr/man8/slattach.8.gz
/usr/share/man/man5/ethers.5.gz
/usr/share/man/man8/arp.8.gz
/usr/share/man/man8/ether-wake.8.gz
/usr/share/man/man8/ifconfig.8.gz
/usr/share/man/man8/ipmaddr.8.gz
/usr/share/man/man8/iptunnel.8.gz
/usr/share/man/man8/mii-diag.8.gz
/usr/share/man/man8/mii-tool.8.gz
/usr/share/man/man8/nameif.8.gz
/usr/share/man/man8/netstat.8.gz
/usr/share/man/man8/plipconfig.8.gz
/usr/share/man/man8/route.8.gz
/usr/share/man/man8/slattach.8.gz
/usr/share/man/pt/man8/arp.8.gz
/usr/share/man/pt/man8/ifconfig.8.gz
/usr/share/man/pt/man8/netstat.8.gz
/usr/share/man/pt/man8/route.8.gz

[root@rocky8 ~]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.31.1.8  netmask 255.255.248.0  broadcast 172.31.7.255
        inet6 fe80::20c:29ff:fef9:6ad1  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:f9:6a:d1  txqueuelen 1000  (Ethernet)
        RX packets 22894  bytes 32929773 (31.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2364  bytes 214404 (209.3 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 8  bytes 832 (832.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8  bytes 832 (832.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ifconfig [interface]
ifconfig -a
ifconfig IFACE [up|down]
ifconfig interface [aftype] options | address ...
ifconfig IFACE IP/netmask [up]
ifconfig IFACE IP netmask NETMASK

注意:立即生效

启用混杂模式:[-]promisc

范例:

#添加一块网卡

[root@centos6 ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:29:18:63:F7  
          inet addr:172.31.0.66  Bcast:172.31.7.255  Mask:255.255.248.0
          inet6 addr: fe80::20c:29ff:fe18:63f7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:87 errors:0 dropped:0 overruns:0 frame:0
          TX packets:67 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:12998 (12.6 KiB)  TX bytes:11638 (11.3 KiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
#默认是看不到的

[root@centos6 ~]# ifconfig -a #可以看到被禁用的网卡
eth0      Link encap:Ethernet  HWaddr 00:0C:29:18:63:F7  
          inet addr:172.31.0.66  Bcast:172.31.7.255  Mask:255.255.248.0
          inet6 addr: fe80::20c:29ff:fe18:63f7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:97 errors:0 dropped:0 overruns:0 frame:0
          TX packets:73 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:13888 (13.5 KiB)  TX bytes:13274 (12.9 KiB)

eth1      Link encap:Ethernet  HWaddr 00:0C:29:18:63:01  
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

[root@centos6 ~]# ifconfig eth1 up #启用网卡
[root@centos6 ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:29:18:63:F7  
          inet addr:172.31.0.66  Bcast:172.31.7.255  Mask:255.255.248.0
          inet6 addr: fe80::20c:29ff:fe18:63f7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:125 errors:0 dropped:0 overruns:0 frame:0
          TX packets:93 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:16390 (16.0 KiB)  TX bytes:16556 (16.1 KiB)

eth1      Link encap:Ethernet  HWaddr 00:0C:29:18:63:01  
          inet6 addr: fe80::20c:29ff:fe18:6301/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 b)  TX bytes:238 (238.0 b)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

[root@centos6 ~]# ifconfig eth0:1 172.31.0.76/21 #设置网卡别名IP地址
[root@centos6 ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:29:18:63:F7  
          inet addr:172.31.0.66  Bcast:172.31.7.255  Mask:255.255.248.0
          inet6 addr: fe80::20c:29ff:fe18:63f7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:201 errors:0 dropped:0 overruns:0 frame:0
          TX packets:144 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:23544 (22.9 KiB)  TX bytes:23762 (23.2 KiB)

eth0:1    Link encap:Ethernet  HWaddr 00:0C:29:18:63:F7  
          inet addr:172.31.0.76  Bcast:172.31.7.255  Mask:255.255.248.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth1      Link encap:Ethernet  HWaddr 00:0C:29:18:63:01  
          inet6 addr: fe80::20c:29ff:fe18:6301/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 b)  TX bytes:468 (468.0 b)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

[root@centos6 ~]# ifconfig eth0:1 down #禁用网卡别名

[root@centos6 ~]# ifconfig eth1 172.31.0.86/21
[root@centos6 ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:29:18:63:F7  
          inet addr:172.31.0.66  Bcast:172.31.7.255  Mask:255.255.248.0
          inet6 addr: fe80::20c:29ff:fe18:63f7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:273 errors:0 dropped:0 overruns:0 frame:0
          TX packets:191 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:30284 (29.5 KiB)  TX bytes:30720 (30.0 KiB)

eth1      Link encap:Ethernet  HWaddr 00:0C:29:18:63:01  
          inet addr:172.31.0.86  Bcast:172.31.7.255  Mask:255.255.248.0
          inet6 addr: fe80::20c:29ff:fe18:6301/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 b)  TX bytes:468 (468.0 b)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

[root@centos6 ~]# ifdown eth1
usage: ifdown <device name>
#禁用不了,因为eth1没有网卡配置文件
#ifdown  eth1只是删除了IP地址,ifconfig eth1 down  是禁用了网卡

[root@centos6 ~]# ifconfig eth1 0/0  这样也可以清除IP地址
SIOCSIFNETMASK: Cannot assign requested address
SIOCGIFADDR: Cannot assign requested address
SIOCSIFBROADCAST: Cannot assign requested address

[root@centos6 ~]# ifconfig -s
Iface   MTU Met    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0       1500   0      387      0      0      0      273      0      0      0 BMRU
eth1       1500   0        0      0      0      0        6      0      0      0 BMRU
lo        65536   0        0      0      0      0        0      0      0      0 LRU
#-s  统计网卡流量

[root@rocky8 ~]# watch -n0.5 ifconfig -s
Every 0.5s: ifconfig -s                                                                                        rocky8: Mon Oct 25 18:25:14 2021

Iface	   MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0             1500    22994      0	   0 0          2452	  0	 0	0 BMRU
eth1             1500        7      0	   0 0            16	  0	 0	0 BMRU
lo              65536        8      0	   0 0             8	  0	 0	0 LRU

[root@centos7 ~]# ping -f 172.31.1.8 #-f  flood  泛洪
PING 172.31.1.8 (172.31.1.8) 56(84) bytes of data.

在这里插入图片描述

[root@centos7 ~]# ping -s 65508 -f 172.31.1.8
Error: packet size 65508 is too large. Maximum is 65507
#-s 指定一次多少字节 ,最大65507字节

[root@centos7 ~]# ping -s 65507 -f 172.31.1.8
PING 172.31.1.8 (172.31.1.8) 65507(65535) bytes of data.

在这里插入图片描述
范例:

[root@rocky8 ~]# ifconfig eth0 10.0.0.68 netmask 255.255.0.0

#清除eth0上面的IP地址
[root@rocky8 ~]# ifconfig eth0 0.0.0.0/0

#启用和禁用网卡
[root@rocky8 ~]# ifconfig eth0 down
[root@rocky8 ~]# ifconfig eth0 up

#对一个网卡设置多个IP地址
[root@rocky8 ~]# ifconfig eth0:1 172.16.0.8/24
[root@rocky8 ~]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.31.1.8  netmask 255.255.248.0  broadcast 172.31.7.255
        inet6 fe80::20c:29ff:fef9:6ad1  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:f9:6a:d1  txqueuelen 1000  (Ethernet)
        RX packets 22234  bytes 32826530 (31.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1892  bytes 160671 (156.9 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth0:1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.16.0.8  netmask 255.255.255.0  broadcast 172.16.0.255
        ether 00:0c:29:f9:6a:d1  txqueuelen 1000  (Ethernet)

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@rocky8 ~]# ifconfig eth0:1 down
[root@rocky8 ~]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.31.1.8  netmask 255.255.248.0  broadcast 172.31.7.255
        inet6 fe80::20c:29ff:fef9:6ad1  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:f9:6a:d1  txqueuelen 1000  (Ethernet)
        RX packets 22244  bytes 32827424 (31.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1900  bytes 162751 (158.9 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

范例:

[root@rocky8 ~]# ifconfig -s
Iface      MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0             1500    22251      0      0 0          1908      0      0      0 BMRU
lo              65536        0      0      0 0             0      0      0      0 LRU
[root@rocky8 ~]# ifconfig -s eth0
Iface      MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0             1500    22265      0      0 0          1917      0      0      0 BMRU

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