Hcip day 6 notes

OSPF Irregular areas of
    OSPF Requirements for area division ：
        1, There must be... Between areas ABR
        2, Regions must be divided according to star topology

1, Non backbone areas away from the backbone
2, Discontinuous backbone          Most of them appear in the process of network upgrading

1, adopt VPN The tunnel will R4 Connect to the backbone area , Legalize it
    1, When a router connects backbone areas and multiple non backbone areas at the same time , Routing information can be directly transmitted between non backbone areas without going through the backbone .
    2, If a router routes information directly from regionalism , At the same time from other ABR Learn the same routing information ,
        The router will unconditionally trust the routing information it has learned , Even if the cost value is greater than others .

summary ---VPN The disadvantage of tunnel solving the problem of irregular area
    1, It may cause poor route selection
    2, It may cause repeated updates
    3, because R2 and R4 Need to build neighborhoods , Therefore, data sent periodically , Cause area 1 Waste of link resources

2, Use OSPF Virtual link solves the problem of irregular area --- The virtual link always belongs to the region 0
    [r4-ospf-1-area-0.0.0.1]vlink-peer 2.2.2.2

    [r4]display ospf vlink --- View virtual link information

    summary --- Virtual link has the disadvantage of solving the problem of irregular area
    1, The virtual link establishes a neighbor relationship with the party members , therefore , It will also send periodic data to keep alive , It will also cause a waste of resources in the crossing area
    2, Limit to only one area

3, Multi process bidirectional republication
    Our republication is configured to run different protocols （ Different processes of the same protocol ） On the border router ,
        Such a border router is called ASBR --- Autonomous system border router （ Protocol boundary router ）
    summary --- Virtual link solves the problem of irregular area --- First , Republishing as a solution will not cause periodic data consumption of resources , There will be no poor routing and repeated updates ,
        however , Because the imported route is recognized as an extraterritorial route , Its controllability is low , therefore , Set a lower priority .

OSPF Of LSA

    LSA ---- Link status notification --- OSPF The protocol is produced in different network environments , Used to carry and convey different information
    LSDB --- Link state database ---

    OSPFV2 Version requirements must be mastered LSA There are six types

LSA Head
    TYPE --- type --- It stands for LSA The type of
    LinkState ID --- Link state identifier --- Its function is to mark a LSA Information , It's equivalent to this LSA The name of .
    advRouter --- Notify router --- Just send this LSA Information router RID

    The above three parameters are called LSA A triple , Through these three parameters, we can uniquely calibrate a LSA Information .
    [r3]display ospf lsdb router 4.4.4.4 --- Expand a LSA Content

    LSA Aging time --- Company S --- When LSA Set to... When generated by the originating router 0（ Not to join LSDB Then time it ）,
        after , The LSA Spread in the network ,LSA The aging time will also accumulate all the time . Under normal circumstances ,LS The aging time will not exceed 1800 second --- MAX AGE --- 3600S.
        When one LSA The aging time of information reaches 3600S when , It will be determined that LSA Information failure , Directly from LSDB Delete in

SEQ --- Serial number --- By nature 32 Bit binary structure ---   Each router sends the same message LSA Will carry a serial number , also , This serial number will be added one by one 1, Is a judgment LSA New and old important parameters .
    Linear sequence space --- advantage ： The old and new relationship is well confirmed ; shortcoming ： When the serial number space is used up, the old and new relationships cannot be compared
    Cyclic sequence space --- advantage ： The serial number space can be recycled ; shortcoming ： When the difference between two serial numbers is too large , It will be impossible to judge the old and new relationship
    Lollipop type sequence space --- OSPF Using the lollipop sequence space , However, in order to avoid entering the circular space, the relationship between the old and the new cannot be judged ,
        therefore ,OSPF It is required not to enter the cycle （ It is equivalent to using linear sequence space --- The value range is equivalent to from 0X80000001-0X7FFFFFFE)

    OSPF Method of refreshing space serial number --- When one LSA When the serial number of the message reaches the maximum , The device sends the message LSA This message will be at the same time LSA Set the aging time of as the maximum aging time --- 3600S,
        The neighbor received this LSA After the message , Because the serial number is the latest serial number , The local corresponding... Will be replaced LSA Information , after , And because the aging time is 3600S, Then the LSA Information deletion .
        The local device will send another same message LSA, And the serial number is 0X80000001, The neighbors will send the latest LSA The information is stored in the database , Refresh the serial number space .

chksum --- The checksum --- This checksum will also participate in LSA Old and new judgments , When two LSA When the serial numbers of are the same , Compare checksums , Large checksum is new .

OSPF Periodic update of --- Every one of them LSA The aging time reaches 180S when , Periodic updates will be made .
    Group pace timer --- 300S --- When there is LSA The aging time reaches 1800S when , Periodic updates are not performed immediately , But wait 300S, When reach 2100S when , Will update all at the same time 1800S Of LSA Information

type            LSID         Notifier         The scope of communication             The information carried

Type-1 LSA Router         Announcer's RID             Each machine in the network runs OSPF     Single area               Local interface direct connection topology information
                        Protocol router RID

Type-2 LSA Network     DR Interface IP Address         Single MA In the network DR Corresponding
                        Of routers RID         Single area               Single MA Supplementary information about the network

Type-3 LSA
Sum-Net(Summary)       The network number of the inter domain route      ABR            

Type-1 LSA --- Every device in the whole network will send 1 class LSA, And send only one .

    LINK --- Describe the connection of router interface , The connection information of an interface can pass through multiple channels LINK To describe
        type --- Link type , It is mainly through the network type of the interface to judge what kind of network our interface is connected to

Type-2 LSA --- because 1 class LSA Can't completely express MA Complete information of the network , therefore , Need to introduce class II LSA Supplement the missing information

    2 class LSA It's a MA The Internet only has DR Send one message to the corresponding device . because ,2 class LSA All the information described in is public information , therefore , Sending multiple times will result in repeated updates

    All routing information must be available through topology information （1 Classes and 2 class LSA） Check calculation . --- The so-called checking calculation means that you must pass 1 Classes and 2 class LSA Information to calculate the location of the notification router

Type-3 LSA --- It transmits inter domain routing information , It should be noted that 3 class LSA Cost value carried in , It refers to the cost of the advertiser reaching the target network segment .
        The cost value of the route added with the table needs to use the carrying cost value plus the cost value of the local arrival advertiser .