<Jeremy's IT Lab> Day 28: OSPF (part 3)

OSPF (part 3)

 

Loop back: virtual int (defualt up/up state; provide consistent IP adrs)

 

Type of OSPF:

1. broad cast

- default on Ethernet, FDDI(Fiber Distributed Data Interface)

-> use multicast adrs <224.0.0.5>

-> DR/ BDR must be elected each subnet (if no OSPF, DR only)

-> Neither DR/BDR, DROther (2-way state; not exchange LSAs)

-> when DR goes down, BDR becomes DR (regardlness DROther's priority)

-> priority:

   (1) highest OSPF int priority (default 1)

   (2) highest OSPF Router ID

-> hello 10 sec, dead time 40 sec

 

2. Point-to-Point (legacy)

- default on PPP(point to point protocol), HDLC(High-level Data link Control)

-> use multicast adrs <224.0.0.5>

-> L2 encapsulation

-> DR/BDR not elected

-> One side DCE(Data Communications Equipment), other side DTE(Data Termianl Equipment)

-> router formed full adjacency

-> // clock rate (diff btw speed in Ethernet protocol)

-> hello 10 sec, dead time 40 sec

 

3. Non-broadcast

- default on Frame Relay, X.25 (out of CCNA)

-> hello 30 sec, dead time 120 sec

 

OSPF Requirment:

1. Must match Area Number | Subnet(area) |  Hello, Dead timers | Authentication setting | IP MTU | OSPF NW Type

2. Must be unnique OSPF ID

 

OSPF LSA Types:

-> LSDB made of LSA

-> 11 types (CCNA only handle 3)

->types:

   (1) Type 1(Router LSA)

       - all router generated

       - identifies Router ID

       - list NW attached to Router's OSPF-activated int

   (2) Type 2(NW LSA)

       - generated by DR

       - list routers which attached to multi access NW

(3) Type 3(AS-External LSA)

       - generated by ASBR