WOLF-LAB沃尔夫网络实验室中国网络精英的发源地!
24小时咨询热线:173-1636-2402

新闻资讯

News

您当前位置: 新闻资讯 > 华为技术 > 详情

HCIE培训理论技术学习LSDB(链路状态数据库)的同步实验-WOLFLAB

发布日期:2023-04-28 浏览次数:1865 来源:崔志鹏

HCIE培训理论技术学习LSDB(链路状态数据库)的同步-WOLFLAB


华为认证HCIE培训课程.jpg

WOLFLAB官方微信:17316362402,HCIE培训理论技术学习可联系WOLFLAB网络技术实验室,了解HCIE培训价格多少钱,HCIE培训考试费用多少钱,HCIE培训开班情况等!


HCIE培训中  IS-IS的LSP交互过程

LSP产生的原因

IS-IS路由域内的所有路由器都会产生LSP,以下事件会触发一个新的LSP:

邻居Up或Down

IS-IS相关接口Up或Down

引入的IP路由发生变化

区域间的IP路由发生变化

接口被赋了新的metric值

周期性更新

HCIE培训中 收到邻居新的LSP的处理过程

1. 将接收的新的LSP合入到自己的LSDB数据库中,并标记为flooding。

2. 发送新的LSP到除了收到该LSP的接口之外的接口。

3. 邻居再扩散到其他邻居。

LSP的“泛洪”

LSP报文的“泛洪”(flooding)是指当一个路由器向相邻路由器通告自己的LSP后,相邻路由器再将同样的LSP报文传送到除发送该LSP的路由器外的其它邻居,并这样逐级将LSP传送到整个层次内所有路由器的一种方式。通过这种“泛洪”,整个层次内的每一个路由器就都可以拥有相同的LSP信息,并保持LSDB的同步。

每一个LSP都拥有一个标识自己的4字节的序列号。在路由器启动时所发送的第一个LSP报文中的序列号为1,以后当需要生成新的LSP时,新LSP的序列号在前一个LSP序列号的基础上加1。更高的序列号意味着更新的LSP。

 

P2P网络LSDB同步过程如下:

为了实现LSDB的同步,两台设备在邻居关系建立起来之后彼此发送CSNP报文,里面携带LSP的头部信息

图片1(44).png

R1发送的CSNP:

Frame 40: 71 bytes on wire (568 bits), 71 bytes captured (568 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Complete Sequence Numbers Protocol Data Unit

    PDU length: 67

    Source-ID: 0000.0000.0001

    Source-ID-Circuit: 00

    Start LSP-ID: 0000.0000.0000.00-00

    End LSP-ID: ffff.ffff.ffff.ff-ff

    LSP entries (t=9, l=32)

        Type: 9

        Length: 32

        LSP Entry

            LSP Sequence Number: 0x0000000c

            Remaining Lifetime: 1191

            LSP checksum: 0x4a16

        LSP-ID: 0000.0000.0001.00-00

 

R2发送的CSNP:

Frame 39: 71 bytes on wire (568 bits), 71 bytes captured (568 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Complete Sequence Numbers Protocol Data Unit

    PDU length: 67

    Source-ID: 0000.0000.0002

    Source-ID-Circuit: 00

    Start LSP-ID: 0000.0000.0000.00-00

    End LSP-ID: ffff.ffff.ffff.ff-ff

    LSP entries (t=9, l=32)

        Type: 9

        Length: 32

        LSP Entry

            LSP Sequence Number: 0x0000000e

            Remaining Lifetime: 1192

            LSP checksum: 0x56fe

        LSP-ID: 0000.0000.0002.00-00

 

同步的规则:交换彼此没有的LSP以及新的LSP替换老旧的LSP,实现LSDB的同步。

 

为了实现同步,对LSP的数据结构做出定义要能实现如下功能:

如何唯一的区分一条LSP呢?

ISIS协议定义通过LSP ID唯一的区分一条LSP

0000.0000.0001.00-00             //8个字节由三个部分组成

LSP ID=system id(6字节)+伪节点标识符(1字节)+分片标识符(1字节)

system id:表示LSP产生路由器的system id,类似于ADV ROUTER;

伪节点标识符:取值0或者非0,如果等于0,则代表该LSP是实节点LSP。如果是非0,则代表该LSP是伪节点LSP,此时system id就是DIS的system id。

分片标识符:用于描述同一台路由器产生的不同的LSP

 

为什么分片呢?

假设一台路由器需要描述的链路信息特别的多,用一条LSP装不下,就会通过多条LSP进行携带,并且泛洪给邻居,有点像IP报文的分片。

举例:下图就是一台路由器产生的多个实节点LSP

0000.0000.0001.00-00 

0000.0000.0001.00-01

0000.0000.0001.00-02

举例:下图就是一台路由器产生的多个伪节点LSP

R1作为多个二层广播域的DIS

0000.0000.0001.01-00 

0000.0000.0001.02-00

 

LSP的新旧判断机制:

1、比较LSP seq,越大越新。

2、seq相同,则判断remain lifetime是否为0,如果等于0,则认为是最新的LSP,用于删除一条LSP。ISIS的holdtime是倒计时,越来越小,OSPF是越来越大。remain lifetime的初始值是1200s,每隔15min,即900s周期性泛红更新LSP,同时序列号+1。

3、如果remain lifetime都不等于0,则比较checksum,越大越新。

4、如果checksum一样,则认为是相同的LSP。

注意:isis的seq的初始值是从1开始,最大值是全F。

 

什么叫撤销一条LSP?

假设AR1上写两条静态路由,并将静态路由引入ISIS。

ip route-static 192.168.1.0 255.255.255.0 NULL0

ip route-static 192.168.2.0 255.255.255.0 NULL0

 

@此时R1就会产生一条LSP,里面携带两条路由;

@R1针对外部路由采用分片的LSP去携带;

图片1(45).png

@此时R1产生这条分片的LSP seq=1

Frame 817: 57 bytes on wire (456 bits), 57 bytes captured (456 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Link State Protocol Data Unit

    PDU length: 53

    Remaining lifetime: 1198

    LSP-ID: 0000.0000.0001.00-01

    Sequence number: 0x00000001

    Checksum: 0x788d [correct]

    [Checksum Status: Good]

    Type block(0x03): Partition Repair:0, Attached bits:0, Overload bit:0, IS type:3

    IP External reachability (t=130, l=24)

        Type: 130

        Length: 24

        IPv4 prefix: 192.168.1.0/24

        IPv4 prefix: 192.168.2.0/24

@如果将引入的静态命令拿掉,此时LSP就会重新产生一条LSP,里面不携带路由信息,seq=2,remaining lifetime=0,此时R2就将该LSP从自己的LSP中删除掉。

Frame 994: 31 bytes on wire (248 bits), 31 bytes captured (248 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Link State Protocol Data Unit

    PDU length: 27

    Remaining lifetime: 0

    LSP-ID: 0000.0000.0001.00-01

    Sequence number: 0x00000002

    [Checksum: [missing]]

    [Checksum Status: Not present]

    Type block(0x03): Partition Repair:0, Attached bits:0, Overload bit:0, IS type:3

@如果R1此时再引人静态,又会产生一条LSP,seq=3:

Frame 1085: 57 bytes on wire (456 bits), 57 bytes captured (456 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Link State Protocol Data Unit

    PDU length: 53

    Remaining lifetime: 1197

    LSP-ID: 0000.0000.0001.00-01

    Sequence number: 0x00000003

    Checksum: 0x748f [correct]

    [Checksum Status: Good]

    Type block(0x03): Partition Repair:0, Attached bits:0, Overload bit:0, IS type:3

    IP External reachability (t=130, l=24)

        Type: 130

        Length: 24

        IPv4 prefix: 192.168.1.0/24

        IPv4 prefix: 192.168.2.0/24

@R1此时仅删除一条192.168.2.0/24的路由,此时R1也会产生一条LSP,seq=4,此时R2收到后就用新的LSP替换旧的了:

Frame 1195: 45 bytes on wire (360 bits), 45 bytes captured (360 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Link State Protocol Data Unit

    PDU length: 41

    Remaining lifetime: 1197

    LSP-ID: 0000.0000.0001.00-01

    Sequence number: 0x00000004

    Checksum: 0x1e1e [correct]

    [Checksum Status: Good]

    Type block(0x03): Partition Repair:0, Attached bits:0, Overload bit:0, IS type:3

    IP External reachability (t=130, l=12)

        Type: 130

        Length: 12

        IPv4 prefix: 192.168.1.0/24

 

课件理想过程:

1、邻居关系建立起来之后,两台设备互相发送CSNP,里面携带本设备LSDB中所有的LSP的头部信息;

2、通过比较邻居发送过来的头部信息,我就知道哪些LSP你有我没有,哪些LSP是我有你没有的;

3、我没有的就给邻居发送PSNP进行请求;

@PSNP报文中携带的就是就是六元组

@PSNP报文中的SEQ+checksum+remain lifetime并没有携带的必要,因为OSPF中的LSR只携带了LSA的三要素;

@PSNP报文中SEQ=0,表明该报文为请求报文,下图为理想情况下R2给R1发送的PSNP请求报文;

Frame 35: 39 bytes on wire (312 bits), 39 bytes captured (312 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Partial Sequence Numbers Protocol Data Unit

    PDU length: 35

    Source-ID: 0000.0000.0002

    Source-ID-Circuit: 00

    LSP entries (t=9, l=16)

        Type: 9

        Length: 16

        LSP Entry

            LSP Sequence Number: 0x00000000

            Remaining Lifetime: 1194

            LSP checksum: 0x4a16

        LSP-ID: 0000.0000.0001.00-00

4、R1收到请求报文之后,R2请求的LSP,就是R1的LSP的详细信息;

Frame 32: 88 bytes on wire (704 bits), 88 bytes captured (704 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Link State Protocol Data Unit

    PDU length: 84

    Remaining lifetime: 1195

    LSP-ID: 0000.0000.0001.00-00

    Sequence number: 0x0000000c

    Checksum: 0x4a16 [correct]

    [Checksum Status: Good]

    Type block(0x03): Partition Repair:0, Attached bits:0, Overload bit:0, IS type:3     //这条LSP的相关BIT位

        0... .... = Partition Repair: Not supported

        .000 0... = Attachment: 0

            .... 0... = Error metric: Not set

            .... .0.. = Expense metric: Not set

            .... ..1. = Delay metric: Set

            .... ...1 = Default metric: Set

        .... .0.. = Overload bit: Not set

        .... ..11 = Type of Intermediate System: Level 2 (3)

    Protocols supported (t=129, l=1)                                                                       

    Area address(es) (t=1, l=2)

    IS Reachability (t=2, l=12)                             //描述拓扑信息,R1表明自己P2P的连着02的路由器,因为最后为00,如果是广播型链路R1会说自己连着伪节点,最后肯定不为00

        Type: 2

        Length: 12

        Reserved: 0x00

        IS Neighbor: 0000.0000.0002.00

            ..00 1010 = Default Metric: 10

            .0.. .... = Default Metric: Internal

            ..00 1010 = Delay Metric: 10

            0... .... = Delay Metric: Supported

            .0.. .... = Delay Metric: Internal

            ..00 1010 = Expense Metric: 10

            0... .... = Expense Metric: Supported

            .0.. .... = Expense Metric: Internal

            ..00 1010 = Error Metric: 10

            0... .... = Error Metric: Supported

            .0.. .... = Error Metric: Internal

            IS Neighbor: 0000.0000.0002.00

    IP Interface address(es) (t=132, l=8)                     //会把自己所有运行isis的接口地址携带出去

        Type: 132

        Length: 8

        IPv4 interface address: 1.1.1.1

        IPv4 interface address: 1.1.12.1

    IP Internal reachability (t=128, l=24)                    //携带自己的路由信息

        Type: 128

        Length: 24

        IPv4 prefix: 1.1.1.1/32

            ..00 0000 = Default Metric: 0

            .0.. .... = Default Metric IE: Internal              //表示路由的cost类型

            0... .... = Distribution: Up                      //DU bit

            ..00 0000 = Delay Metric: 0

            1... .... = Delay Metric: Not Supported

            .0.. .... = Delay Metric: Internal

            ..00 0000 = Expense Metric: 0

            1... .... = Expense Metric: Not Supported

            .0.. .... = Expense Metric: Internal

            ..00 0000 = Error Metric: 0

            1... .... = Error Metric: Not Supported

            .0.. .... = Error Metric: Internal

        IPv4 prefix: 1.1.12.0/24

            ..00 1010 = Default Metric: 10

            .0.. .... = Default Metric IE: Internal

            0... .... = Distribution: Up

            ..00 0000 = Delay Metric: 0

            1... .... = Delay Metric: Not Supported

            .0.. .... = Delay Metric: Internal

            ..00 0000 = Expense Metric: 0

            1... .... = Expense Metric: Not Supported

            .0.. .... = Expense Metric: Internal

            ..00 0000 = Error Metric: 0

            1... .... = Error Metric: Not Supported

            .0.. .... = Error Metric: Internal

5、R2收到之后发送一个PSNP进行确认,就是将R1发送过来的LSP中的六元组发在PSNP里面告诉R1我收到你发给我的LSP了

Frame 35: 39 bytes on wire (312 bits), 39 bytes captured (312 bits) on interface -, id 0

Point-to-Point Protocol

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Partial Sequence Numbers Protocol Data Unit

    PDU length: 35

    Source-ID: 0000.0000.0002

    Source-ID-Circuit: 00

    LSP entries (t=9, l=16)

        Type: 9

        Length: 16

        LSP Entry

            LSP Sequence Number: 0x0000000c

            Remaining Lifetime: 1194

            LSP checksum: 0x4a16

        LSP-ID: 0000.0000.0001.00-00

6、如果R1长时间没有收到R2的PSNP,我就会每隔5S重传LSP;

7、ISIS每隔900s周期性更新,谁产生的谁负责更新,就是将该LSP的SEQ+1,checksum重新算,remain lifetime置位1200;

8、设备收到新的LSP,替换自己LSDB现有的旧的LSP,并且LSP的老化时间重新置位1200;

 

实际的过程:

1、邻居关系建立起来之后,两台设备直接互相发送自己所有的LSP;

2、彼此发送PSNP进行确认,表示我收到对端的LSP了;

3、此时LSDB完成同步,两台设备会发送CSNP,里面携带自己LSDB里面所有LSP的头部信息,来验证一下LSDB是否同步;

广播型网络的交互过程

图片1(46).png

HCIE培训循环开班,联系网站客服预约免费试听

实际过程如下:

1、邻居关系建立起来之后,两台设备直接互相发送自己所有的LSP;

注意:两台设备邻居建立之后非DIS会马上发送LSP,DIS 20s之后发送LSP,因为需要通过hello报文会选举DIS,DIS的选举时间是20s,ospf选举DR的时间是40s;

ISIS是邻居关系建立起来之后才去选举DIS,OSPF是邻居关系建立的时候就去选DR,所以为啥ISIS邻居关系建立的那么快;

 

2、假设R2被选举为DIS,此时邻居关系建立起来R1会发送一条实节点LSP,R2会发送一条实节点LSP,一条伪节点LSP;

R1发的:

Frame 26: 101 bytes on wire (808 bits), 101 bytes captured (808 bits) on interface -, id 0

IEEE 802.3 Ethernet 

Logical-Link Control

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Link State Protocol Data Unit

    PDU length: 84

    Remaining lifetime: 1199

    LSP-ID: 0000.0000.0001.00-00

    Sequence number: 0x00000007

    Checksum: 0x6af9 [correct]

    [Checksum Status: Good]

    Type block(0x03): Partition Repair:0, Attached bits:0, Overload bit:0, IS type:3

    Protocols supported (t=129, l=1)

    Area address(es) (t=1, l=2)

    IS Reachability (t=2, l=12)

    IP Interface address(es) (t=132, l=8)

    IP Internal reachability (t=128, l=24)

        Type: 128

        Length: 24

        IPv4 prefix: 1.1.1.1/32

        IPv4 prefix: 1.1.12.0/24

---------------------------------------------------------------

R2发的:

Frame 29: 72 bytes on wire (576 bits), 72 bytes captured (576 bits) on interface -, id 0

IEEE 802.3 Ethernet 

Logical-Link Control

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Link State Protocol Data Unit

    PDU length: 55

    Remaining lifetime: 1199

    LSP-ID: 0000.0000.0002.01-00

    Sequence number: 0x00000002

    Checksum: 0xa2e6 [correct]

    [Checksum Status: Good]

    Type block(0x03): Partition Repair:0, Attached bits:0, Overload bit:0, IS type:3

    Protocols supported (t=129, l=1)

    IS Reachability (t=2, l=23)

        Type: 2

        Length: 23

        Reserved: 0x00

        IS Neighbor: 0000.0000.0002.00

        IS Neighbor: 0000.0000.0001.00

 

Frame 30: 101 bytes on wire (808 bits), 101 bytes captured (808 bits) on interface -, id 0

IEEE 802.3 Ethernet 

Logical-Link Control

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Link State Protocol Data Unit

    PDU length: 84

    Remaining lifetime: 1199

    LSP-ID: 0000.0000.0002.00-00

    Sequence number: 0x00000007

    Checksum: 0x8fca [correct]

    [Checksum Status: Good]

    Type block(0x03): Partition Repair:0, Attached bits:0, Overload bit:0, IS type:3

    Protocols supported (t=129, l=1)

    Area address(es) (t=1, l=2)

    IS Reachability (t=2, l=12)

    IP Interface address(es) (t=132, l=8)

    IP Internal reachability (t=128, l=24)

        Type: 128

        Length: 24

        IPv4 prefix: 2.2.2.2/32

        IPv4 prefix: 1.1.12.0/24

3、此时LSDB正式完成同步,两台设备无需发送PSNP确认,因为广播型网络DIS会周期性的每隔发送CSNP,来保证LSDB的同步;

Frame 37: 100 bytes on wire (800 bits), 100 bytes captured (800 bits) on interface -, id 0

IEEE 802.3 Ethernet 

Logical-Link Control

ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol

ISO 10589 ISIS Complete Sequence Numbers Protocol Data Unit

    PDU length: 83

    Source-ID: 0000.0000.0002

    Source-ID-Circuit: 00

    Start LSP-ID: 0000.0000.0000.00-00

    End LSP-ID: ffff.ffff.ffff.ff-ff

    LSP entries (t=9, l=48)

        Type: 9

        Length: 48

        LSP Entry

        LSP-ID: 0000.0000.0001.00-00

        LSP Entry

        LSP-ID: 0000.0000.0002.00-00

        LSP Entry

        LSP-ID: 0000.0000.0002.01-00

 

课件上的情况如下:

前提:新加入的路由器RouterC不会将DIS抢走

图片1(47).png

@B和C一旦建立邻居就会互相发送自身LSDB中的LSP;

@A和C也会建立邻居,但是不会交互LSDB中的LSP,避免重复发送;

@非DIS路由器接收到新增路由器的LSP后,如果是新的就直接添加到自己的LSP,并且不会发送PSNP确认,并向其他链路上的邻居泛洪这些LSP;

@此时LSDB完成同步,DIS会周期性的每隔10s发送CSNP,携带自己LSDB中的头部信息;

@如果新增路由器收到DIS的CSNP,比较自身的LSDB,发现有的LSP我没有则发送PSNP,DIS接收此PSNP,发送LSP。C收到后添加到自身的LSDB,不会发送PSNP确认这些LSP,同步结束,并向其他链路泛洪;

@DIS每10s周期性发送CSNP,维护广播型网络上路由器的LSDB同步;

@万一我没有收到,就根据DIS周期性发送的CSNP,然后我发送PSNP请求就行;


HCIE培训开班咨询可联系WOLFLAB网络实验室网站客服

我们会陆续更新CCNA|CCNP|EI CCIE;HCIA|HCIP|HCIE Datacom|VMware等学习视频,IT技术,学习技巧等

https://www.wolf-lab.com/

WOLFLAB官方微信:17316362402

WOLFLAB官方QQ:2569790740

返回目录
在线咨询