主要用于运营商的内部网络
① IS指路由器
② ISIS属于大型内部网关路由协议类似OSPF,多用于运营商,企业网很少使用
③ 使用SPF算法,链路状态类路由协议
④ ISIS封装数据包是基于OSI模型、OSPF、RIP、以及常见的以太网数据包封装都是基于TCP/IP模型
⑤ ISIS划分区域是基于路由器的。即一个路由器只能属于一个区域
⑥ ISIS也是两层架构(骨干区域、常规区域)
① Level 1路由器:仅收发L1 isis报文
② Level 2路由器:仅收发L2 isis报文
③ Level 1 2路由器:可以收发L1和L2的isis报文
连续的一片Level 2路由器(包含L1 2)的集合
注:
①默认情况下所有运行ISIS的路由器都是Level 12路由器
②L12 路由器类似OSPF中ABR
L2 路由器类似OSPF中骨干区域路由器
L1 路由器类似OSPF中常规区域路由器
system-view //进入系统视图
[Huawei]undo info-center enable //关闭信息告警提示
[Huawei]sysname R1 // 改名
[R1]interface g0/0/0 //进入接口
[R1-GigabitEthernet0/0/0]ip address 12.1.1.1 24 //设置IP地址
[R1-GigabitEthernet0/0/0]quit //退出
[R1]interface LoopBack 0 //进入环回接口
[R1-LoopBack0]ip address 1.1.1.1 24 //设置IP地址
[R1-LoopBack0]quit //退出
[R1]interface LoopBack 8 //进入环回接口
[R1-LoopBack8]ip address 8.8.8.8 24 //设置IP地址
[R1-LoopBack8]quit //退出
[R1]
system-view //进入系统视图
[Huawei]undo info-center enable //关闭信息告警
[Huawei]sysname R2 //改名
[R2]interfac g0/0/0 //进入接口
[R2-GigabitEthernet0/0/0]ip address 12.1.1.2 24 //设置IP地址
[R2-GigabitEthernet0/0/0]quit // 退出
[R2]interface LoopBack 0 // 进入环回接口
[R2-LoopBack0]ip address 2.2.2.2 24 //设置Ip地址
[R2-LoopBack0]quit // 退出
[R2]interface g0/0/1 // 进入接口
[R2-GigabitEthernet0/0/1]ip address 23.1.1.2 24 // 设置IP地址
[R2-GigabitEthernet0/0/1]quit // 退出
[R2]
system-view //进入系统视图
[Huawei]undo info-center enable // 关闭信息告警提示
[Huawei]sysname R3 // 改名
[R3]interface g0/0/0 //进入接口
[R3-GigabitEthernet0/0/0]ip address 23.1.1.3 24 // 设置IP地址
[R3-GigabitEthernet0/0/0]quit // 退出
[R3]interface LoopBack 0 // 进入环回接口
[R3-LoopBack0]ip address 3.3.3.3 24 // 设置IP地址
[R3-LoopBack0]quit // 退出
[R3]interface g0/0/1 // 进入接口
[R3-GigabitEthernet0/0/1]ip address 34.1.1.3 24 // 设置IP地址
[R3-GigabitEthernet0/0/1]quit // 退出
[R3]
system-view //进入系统视图
[Huawei]undo info-center enable // 关闭信息告警提示
[Huawei]sysname R4 // 改名
[R4]interface g0/0/0 // 进入接口
[R4-GigabitEthernet0/0/0]ip address 34.1.1.4 24 // 设置IP地址
[R4-GigabitEthernet0/0/0]quit // 退出
[R4]interface LoopBack 0 // 进入环回接口
[R4-LoopBack0]ip address 4.4.4.4 24 // 设置IP地址
[R4-LoopBack0]quit // 退出
[R4]interface g0/0/1 // 进入接口
[R4-GigabitEthernet0/0/1]ip address 45.1.1.4 24 // 设置IP地址
[R4-GigabitEthernet0/0/1]quit // 退出
[R4]
system-view //进入系统视图
[Huawei]undo info-center enable // 关闭信息告警提示
[Huawei]sysname R5 // 改名
[R5]interface g0/0/0 // 进入接口
[R5-GigabitEthernet0/0/0]ip address 45.1.1.5 24 //设置IP地址
[R5-GigabitEthernet0/0/0]quit // 退出
[R5]interface LoopBack 0 // 进入环回接口
[R5-LoopBack0]ip address 5.5.5.5 24 // 设置IP地址
[R5-LoopBack0]quit // 退出
[R5]
配置网络实体标识,类似OSPF中的Route-ID,标识该中间系统(路由表)的身份信息。
其中49.0002表示路由器所在的区域。
0000.0000.1111表示系统ID即Router-ID.00固定格式
[R1]isis // 进入ISIS
[R1-isis-1]network-entity 49.0002.0000.0000.1111.00 //设置路由器所在区域和路由器ID
[R1-isis-1]quit //退出
[R1]
[R2]isis //进入ISIS
[R2-isis-1]network-entity 49.0002.0000.0000.2222.00 //设置路由器所在区域和路由器ID
[R2-isis-1]quit //退出
[R2]
[R3]isis //进入ISIS
[R3-isis-1]network-entity 49.0001.0000.0000.3333.00 //设置路由器所在区域和路由器ID
[R3-isis-1]quit //退出
[R3]
[R4]isis //进入ISIS
[R4-isis-1]network-entity 49.0003.0000.0000.4444.00 //设置路由器所在区域和路由器ID
[R4-isis-1]quit //退出
[R4]
[R5]isis //进入ISIS
[R5-isis-1]network-entity 49.0003.0000.0000.5555.00 //设置路由器所在区域和路由器ID
[R5-isis-1]quit //退出
[R5]
[R1]interface g0/0/0 //进入接口
[R1-GigabitEthernet0/0/0]isis enable 1 //宣告网段
[R1-GigabitEthernet0/0/0]quit //退出
[R1]interface LoopBack 0 //进入环回接口
[R1-LoopBack0]isis enable 1 //宣告网段
[R1-LoopBack0]quit //退出
[R1]rip //进入RIP
[R1-rip-1]version 2 //协议2
[R1-rip-1]undo summary //关闭自动汇总
[R1-rip-1]network 8.0.0.0 //宣告网段
[R1-rip-1]quit //退出
[R1]
[R2]interface g0/0/0 //进入接口
[R2-GigabitEthernet0/0/0]isis enable 1 //宣告网段
[R2-GigabitEthernet0/0/0]quit //退出
[R2]interface g0/0/1 //进入接口
[R2-GigabitEthernet0/0/1]isis enable 1 //宣告网段
[R2-GigabitEthernet0/0/1]quit //退出
[R2]interface LoopBack 0 //进入环回接口
[R2-LoopBack0]isis enable 1 //宣告网段
[R2-LoopBack0]quit //退出
[R2]
[R3]interface g0/0/0 //进入接口
[R3-GigabitEthernet0/0/0]isis enable 1 //宣告网段
[R3-GigabitEthernet0/0/0]quit //退出
[R3]interface g0/0/1 //进入接口
[R3-GigabitEthernet0/0/1]isis enable 1 //宣告网段
[R3-GigabitEthernet0/0/1]quit //退出
[R3]interface LoopBack 0 //进入换回接口
[R3-LoopBack0]isis enable 1 //宣告网段
[R3-LoopBack0]quit //退出
[R3]
[R4]interface g0/0/0 //进入接口
[R4-GigabitEthernet0/0/0]isis enable 1 //宣告网段
[R4-GigabitEthernet0/0/0]quit //退出
[R4]interface g0/0/1 //进入接口
[R4-GigabitEthernet0/0/1]isis enable 1 //宣告网段
[R4-GigabitEthernet0/0/1]quit //退出
[R4]interface LoopBack 0 //进入环回接口
[R4-LoopBack0]isis enable 1 //宣告网段
[R4-LoopBack0]quit //退出
[R4]
[R5]interface g0/0/0 //进入接口
[R5-GigabitEthernet0/0/0]isis enable 1 //宣告网段
[R5-GigabitEthernet0/0/0]quit //退出
[R5]interface LoopBack 0 //进入环回接口
[R5-LoopBack0]isis enable 1 //宣告网段
[R5-LoopBack0]quit //退出
[R5]
R3——查看路由表
[R3]dis ip routing-table //查看路由表
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 19 Routes : 19
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.0/24 ISIS-L2 15 20 D 23.1.1.2 GigabitEthernet
0/0/0
2.2.2.0/24 ISIS-L2 15 10 D 23.1.1.2 GigabitEthernet
0/0/0
3.3.3.0/24 Direct 0 0 D 3.3.3.3 LoopBack0
3.3.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
3.3.3.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
4.4.4.0/24 ISIS-L2 15 10 D 34.1.1.4 GigabitEthernet
0/0/1
5.5.5.0/24 ISIS-L2 15 20 D 34.1.1.4 GigabitEthernet
0/0/1
12.1.1.0/24 ISIS-L2 15 20 D 23.1.1.2 GigabitEthernet
0/0/0
23.1.1.0/24 Direct 0 0 D 23.1.1.3 GigabitEthernet
0/0/0
23.1.1.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
23.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
34.1.1.0/24 Direct 0 0 D 34.1.1.3 GigabitEthernet
0/0/1
34.1.1.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
34.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
45.1.1.0/24 ISIS-L2 15 20 D 34.1.1.4 GigabitEthernet
0/0/1
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
[R3]
//除了RIP的路由,其他路由都学到了
注:默认情况下,骨干区域的路由不会发送到L1路由器(常规区域),且L1路由器会自动形成指向L12路由器的缺省路由。(这种特性类似OSPF中的totally stub)
[R1]isis //进入ISIS
[R1-isis-1]is-level level-1 //修改路由器的类型为L1
[R1-isis-1]quit //退出
[R1]
[R1]dis ip routing-table //查看路由表
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 16 Routes : 16
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 ISIS-L1 15 10 D 12.1.1.2 GigabitEthernet //默认增加一条缺省路由
0/0/0
1.1.1.0/24 Direct 0 0 D 1.1.1.1 LoopBack0
1.1.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
1.1.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
2.2.2.0/24 ISIS-L1 15 10 D 12.1.1.2 GigabitEthernet
0/0/0
8.8.8.0/24 Direct 0 0 D 8.8.8.8 LoopBack8
8.8.8.8/32 Direct 0 0 D 127.0.0.1 LoopBack8
8.8.8.255/32 Direct 0 0 D 127.0.0.1 LoopBack8
12.1.1.0/24 Direct 0 0 D 12.1.1.1 GigabitEthernet
0/0/0
12.1.1.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
12.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
23.1.1.0/24 ISIS-L1 15 20 D 12.1.1.2 GigabitEthernet
0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
[R1]
[R3]isis //进入ISIS
[R3-isis-1]is-level level-2 // 修改路由器的类型为L2
[R3-isis-1]quit // 退出
[R3]
[R5]isis // 进入ISIS
[R5-isis-1]is-level level-1 // 修改路由器的类型为L1
[R5-isis-1]quit // 退出
[R5]
[R5]dis ip routing-table // 查看路由表
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 13 Routes : 13
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 ISIS-L1 15 10 D 45.1.1.4 GigabitEthernet // 默认增加一条缺省路由
0/0/0
4.4.4.0/24 ISIS-L1 15 10 D 45.1.1.4 GigabitEthernet
0/0/0
5.5.5.0/24 Direct 0 0 D 5.5.5.5 LoopBack0
5.5.5.5/32 Direct 0 0 D 127.0.0.1 LoopBack0
5.5.5.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
34.1.1.0/24 ISIS-L1 15 20 D 45.1.1.4 GigabitEthernet
0/0/0
45.1.1.0/24 Direct 0 0 D 45.1.1.5 GigabitEthernet
0/0/0
45.1.1.5/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
45.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
[R5]
[R1]dis isis brief //查看ISIS简要信息
ISIS Protocol Information for ISIS(1)
-------------------------------------
SystemId: 0000.0000.1111 System Level: L1 //类型为L1
Area-Authentication-mode: NULL
Domain-Authentication-mode: NULL
Ipv6 is not enabled
ISIS is in invalid restart status
ISIS is in protocol hot standby state: Real-Time Backup
Interface: 12.1.1.1(GE0/0/0)
Cost: L1 10 L2 10 Ipv6 Cost: L1 10 L2 10
State: IPV4 Up IPV6 Down
Type: BROADCAST MTU: 1497
Priority: L1 64 L2 64
Timers: Csnp: L1 10 L2 10 ,Retransmit: L12 5 , Hello: L1 10 L2 10 ,
Hello Multiplier: L1 3 L2 3 , LSP-Throttle Timer: L12 50
Interface: 1.1.1.1(Loop0)
Cost: L1 0 L2 0 Ipv6 Cost: L1 0 L2 0
State: IPV4 Up IPV6 Down
Type: P2P MTU: 1500
Priority: L1 64 L2 64
Timers: Csnp: L12 10 , Retransmit: L12 5 , Hello: 10 ,
Hello Multiplier: 3 , LSP-Throttle Timer: L12 50
[R1]
[R3]dis isis brief //查看ISIS简要信息
ISIS Protocol Information for ISIS(1)
-------------------------------------
SystemId: 0000.0000.3333 System Level: L2 //类型为L2
Area-Authentication-mode: NULL
Domain-Authentication-mode: NULL
Ipv6 is not enabled
ISIS is in invalid restart status
ISIS is in protocol hot standby state: Real-Time Backup
Interface: 23.1.1.3(GE0/0/0)
Cost: L1 10 L2 10 Ipv6 Cost: L1 10 L2 10
State: IPV4 Up IPV6 Down
Type: BROADCAST MTU: 1497
Priority: L1 64 L2 64
Timers: Csnp: L1 10 L2 10 ,Retransmit: L12 5 , Hello: L1 10 L2 10 ,
Hello Multiplier: L1 3 L2 3 , LSP-Throttle Timer: L12 50
Interface: 34.1.1.3(GE0/0/1)
Cost: L1 10 L2 10 Ipv6 Cost: L1 10 L2 10
State: IPV4 Up IPV6 Down
Type: BROADCAST MTU: 1497
Priority: L1 64 L2 64
Timers: Csnp: L1 10 L2 10 ,Retransmit: L12 5 , Hello: L1 10 L2 10 ,
Hello Multiplier: L1 3 L2 3 , LSP-Throttle Timer: L12 50
Interface: 3.3.3.3(Loop0)
Cost: L1 0 L2 0 Ipv6 Cost: L1 0 L2 0
State: IPV4 Up IPV6 Down
Type: P2P MTU: 1500
Priority: L1 64 L2 64
Timers: Csnp: L12 10 , Retransmit: L12 5 , Hello: 10 ,
Hello Multiplier: 3 , LSP-Throttle Timer: L12 50
[R3]
[R5]dis isis brief //查看ISIS简要信息
ISIS Protocol Information for ISIS(1)
-------------------------------------
SystemId: 0000.0000.5555 System Level: L1 //类型为L1
Area-Authentication-mode: NULL
Domain-Authentication-mode: NULL
Ipv6 is not enabled
ISIS is in invalid restart status
ISIS is in protocol hot standby state: Real-Time Backup
Interface: 45.1.1.5(GE0/0/0)
Cost: L1 10 L2 10 Ipv6 Cost: L1 10 L2 10
State: IPV4 Up IPV6 Down
Type: BROADCAST MTU: 1497
Priority: L1 64 L2 64
Timers: Csnp: L1 10 L2 10 ,Retransmit: L12 5 , Hello: L1 10 L2 10 ,
Hello Multiplier: L1 3 L2 3 , LSP-Throttle Timer: L12 50
Interface: 5.5.5.5(Loop0)
Cost: L1 0 L2 0 Ipv6 Cost: L1 0 L2 0
State: IPV4 Up IPV6 Down
Type: P2P MTU: 1500
Priority: L1 64 L2 64
Timers: Csnp: L12 10 , Retransmit: L12 5 , Hello: 10 ,
Hello Multiplier: 3 , LSP-Throttle Timer: L12 50
[R5]
[R2]interface g0/0/0 //进入接口
[R2-GigabitEthernet0/0/0]isis circuit-level level-1 //设置该接口只发送L1报文
[R2-GigabitEthernet0/0/0]quit //退出
[R2]interface g0/0/1 //进入接口
[R2-GigabitEthernet0/0/1]isis circuit-level level-2 //设置该接口只发送L2报文
[R2-GigabitEthernet0/0/1]quit //退出
[R2]
ping 3.3.3.3 //测试是否可以ping 通R3设备
PING 3.3.3.3: 56 data bytes, press CTRL_C to break
Reply from 3.3.3.3: bytes=56 Sequence=1 ttl=254 time=50 ms
Reply from 3.3.3.3: bytes=56 Sequence=2 ttl=254 time=20 ms
Reply from 3.3.3.3: bytes=56 Sequence=3 ttl=254 time=20 ms
Reply from 3.3.3.3: bytes=56 Sequence=4 ttl=254 time=20 ms
Reply from 3.3.3.3: bytes=56 Sequence=5 ttl=254 time=30 ms //ping 通
--- 3.3.3.3 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 20/28/50 ms
[R4]interface g0/0/0 //进入接口
[R4-GigabitEthernet0/0/0]isis circuit-level level-2 //设置该接口只发送L2报文
[R4-GigabitEthernet0/0/0]quit //退出
[R4]interface g0/0/1 //进入接口
[R4-GigabitEthernet0/0/1]isis circuit-level level-1 //设置该接口只发送L1报文
[R4-GigabitEthernet0/0/1]quit //退出
[R4]
ping 3.3.3.3 //测试是否可以ping 通R3设备
PING 3.3.3.3: 56 data bytes, press CTRL_C to break
Reply from 3.3.3.3: bytes=56 Sequence=1 ttl=254 time=10 ms
Reply from 3.3.3.3: bytes=56 Sequence=2 ttl=254 time=40 ms
Reply from 3.3.3.3: bytes=56 Sequence=3 ttl=254 time=30 ms
Reply from 3.3.3.3: bytes=56 Sequence=4 ttl=254 time=30 ms
Reply from 3.3.3.3: bytes=56 Sequence=5 ttl=254 time=40 ms //ping 通
--- 3.3.3.3 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 10/30/40 ms
[R3]dis isis peer //查看邻居表
Peer information for ISIS(1)
System Id Interface Circuit Id State HoldTime Type PRI
-------------------------------------------------------------------------------
0000.0000.2222 GE0/0/0 0000.0000.3333.01 Up 21s L2 64
0000.0000.4444 GE0/0/1 0000.0000.4444.01 Up 8s L2 64
Total Peer(s): 2
[R3]
[R3]dis isis lsdb //查看拓扑表
Database information for ISIS(1)
--------------------------------
Level-2 Link State Database
LSPID Seq Num Checksum Holdtime Length ATT/P/OL
-------------------------------------------------------------------------------
0000.0000.2222.00-00 0x0000001e 0xed40 1084 114 0/0/0
0000.0000.3333.00-00* 0x0000000e 0x9ec3 1045 113 0/0/0
0000.0000.3333.01-00* 0x00000006 0xf484 1045 55 0/0/0
0000.0000.4444.00-00 0x00000017 0xc492 1153 114 0/0/0
0000.0000.4444.01-00 0x00000005 0xb261 1153 55 0/0/0
0000.0000.5555.00-00 0x0000000a 0x96c7 166 110 0/0/0
Total LSP(s): 6
*(In TLV)-Leaking Route, *(By LSPID)-Self LSP, +-Self LSP(Extended),
ATT-Attached, P-Partition, OL-Overload
[R3]
注:默认情况下,向ISIS引入的路由是Level 2的路由
[R1]isis //进入ISIS
[R1-isis-1]import-route rip 1 level-1 //接level 1指的是以level 1的形式引入
[R1-isis-1]quit //退出
[R1]
[R3]dis ip routing-table //查看路由表
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 20 Routes : 20
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.0/24 ISIS-L2 15 20 D 23.1.1.2 GigabitEthernet
0/0/0
2.2.2.0/24 ISIS-L2 15 10 D 23.1.1.2 GigabitEthernet
0/0/0
3.3.3.0/24 Direct 0 0 D 3.3.3.3 LoopBack0
3.3.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
3.3.3.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
4.4.4.0/24 ISIS-L2 15 10 D 34.1.1.4 GigabitEthernet
0/0/1
5.5.5.0/24 ISIS-L2 15 20 D 34.1.1.4 GigabitEthernet
0/0/1
8.8.8.0/24 ISIS-L2 15 84 D 23.1.1.2 GigabitEthernet //RIP路由信息成功引入
0/0/0
12.1.1.0/24 ISIS-L2 15 20 D 23.1.1.2 GigabitEthernet
0/0/0
23.1.1.0/24 Direct 0 0 D 23.1.1.3 GigabitEthernet
0/0/0
23.1.1.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
23.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
34.1.1.0/24 Direct 0 0 D 34.1.1.3 GigabitEthernet
0/0/1
34.1.1.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
34.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
45.1.1.0/24 ISIS-L2 15 20 D 34.1.1.4 GigabitEthernet
0/0/1
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
[R3]
写在最后面
看不懂的没关系
加个友情链接继续看
https://blog.csdn.net/HYD696/article/details/106597882