ccna industrial pdf

ccna industrial pdf.7 Neighbor relationship: Two routers form a neighbor relationship if they share a common data link and can negotiate certain parameters specified in the Hello packet.8 Adjacency (Adjacency) relationship: the relationship established by the neighbors of OSPFs that exchange LSAs with each other, generally speaking, on point-to-point and point-to-multipoint networks neighboring routers can form adjacency relationships, while on Broadcast Multiple Access (BMA) and Non-Broadcast Multiple Access (NBMA) networks. BroadcastMultipleAccess,NBMA) networks, to elect DR and BDR,DR and BDR routers form adjacency relationships with all neighboring routers, but DRother routers cannot form adjacency relationships with each other, only neighbor relationships.9 Designated Router (DR) and Backup Designated Router (BDR): To avoid the significant overhead of establishing full adjacencies between routers, OSPF requires that a DR be elected in a multi-access network, and that each router establish an adjacency with it. The election of a DR is accompanied by the election of a BDR, which takes over the responsibilities of the DR when the DR fails, and all other routers in the same BMA network establish adjacencies only with the DR and the BDR.10 OSPF Router ID: A unique identifier for the running OSPF router, 32 bits in length and in the same format as the IP address.17.1.3 OSPFv2 Packet TypesEach OSPF packet has an OSPF packet header. OSPFv2 data is encapsulated into an IPv4 packet. In this IPv4 packet header, the protocol field is set to 89 and the destination address is set to either a multicast address (224.0.0.5 or 224.0.0.6) or a unicast address. If the OSPFv2 multicast packet is encapsulated in an Ethernet frame, the destination MAC address is also the multicast address: 01-00-5E-00-00-05 or 01.00.5E.00-00-06.OSPFv2 packets include five types, each of which plays its own role in the OSPFv2 routing process.1. Hello packetsHello packets are used to establish and maintain neighbor relationships with other OSPFv2 routers, and the period in which a Hello packet is sent is dependent on the OSPF network type. An OSPFv2 neighbor relationship can only be formed if multiple parameters in the Hello packet are successfully negotiated. The OSPFv2Hello packet format is shown in Figure 17.1, and the meaning of each field is described below.1 Version: the version number of the OSPF. the IPv4 protocol field value is 2 and the IPv6 protocol field value is 3.