The purpose and role of the OSPF protocol should be understood as a CCNA / CCNP nominee. In order to identify the intent of the DR and BDR in combination with the elections process, the CCNA/CCNP examination would ask you.

Designated router and backup elections for OSPF

OSPF’s CPU-intensive routing algorithm. It will affect the router every time the OSPF method is running the first algorithm of the shortest path. In one point-to-point network OSPF event, the Hello regular packet is limited to the 30 minutes for each path insert in the linking state database and the event activated (Default 10secs on a PPP, HDLC, and 30sec Frame relay NBMA).

Both routers will be required to establish a link to the other routers within the same broadcast domain within a multiple Access DVD network where routers are linked to the same broadcast section (numerous routers in one VLAN). Even if an LSA is created, the advertising router needs to multicast an LSA for all neighbours. The further routers the multicast radio network has, the more adjacence. The following is required for two routers: Two routers: / 2 = 1 = 2 (1)

The following adjacent numbers of routers are needed for four routers.

The following number of adjacent routers is needed for ten: [10]2 = 45

Note: DR’s and BDR’s are not chosen on point-to-point links because only one adjacent can be established and the DR and BDR are elected to be efficient. The more routers in a segment you have, the more adjacent the bandwidth is used and the more computing capacity is used by the routers. We ought to decrease the amount of work each router has to do with the next router by choosing a designated router with which to access all other routers.The number of adjacent devices decreases with a decreased processing width and bandwidth by using a designated router in your multi-access broadcast network. When you execute the order on a cisco router that is not DR, all routers type complete adjacent routers. R1#show ip ospf next door

Pri State Dead Season Interface Neighbor ID

1 FULL/DR 39:00 00:00: Ethernet0/0/0/0

You can find that the “Complete” neighbor of your router with the DR is established and the output also sets the neighbor of the DR. The neighbor’s router ID at the above output is, which is the DR.

Events occurring will be announced by DR using the multicast address.

The DR can be performed at the address when advertising any activities on Non-DR computers.

Designated router option and backup:

The DR is chosen according to the highest-priority router. The maximum priority of the router is 1, and the scale from 0 to 255. Setting router priority to 0 ensures that no DR or BDR election is allowed on the interface. If you set the current DR router priority of the BDR to zero, it will automatically abandon the task. The routers that are not elected either as DR or as BDR also form adjacent neighbors, but they do not share information on routing, only hellos are exchanged and sent to 224.0.5.

It is in reality a priority that is defined at an interface level in spite of the name ‘router priority.’
Fastethernet protocol R1(conf)# 0/0 R1 (conf-if) Priority 1 of #ip ospf

Should two or more interfaces with the same router preference in the same broadcast area, the OSPF router ID would be a tie-breaker. What is the electoral process:

1. Any router with an OSPF priority set between 1-255 can try to be DR by adding a Router ID in its hellos DR area to participate in the election. By running the command “debug ip ospf adj” you will see the election process, the election takes place during the 2-way process. 2. In the general broadcast sector, each router examines the Hellos received and considers the priority of other routers. 3. If Hello is given a higher priority by another router, this router avoids saying that it is DR and says the best candidate is DR by putting the DR router ID in the DR of the Hello packets. So a router with top priority is the first criterion for improvement 4. If the priorities for the router are the same, the higher RID router is selected as DR. 5. In case of a hat that has a tie in the value of the router priority becomes the BDR of the next highest priority or next highest router identity (Backup Designated Router). 6. If a new router enters into the network after DR/BDR selection or where an existing router enhances its priority then the existing DR or BDR cannot be preempted, note that the position of the DR and BDR is not pre-emptive. 7. The DR shall be accepted as DR if the DR fails and a further choice shall take place for the BDR. 8. If the former DR returns online, it cannot revive the previous DR

When an event is announced to neighbors by either the DR or the BDR on the common broadcast network, it shall transmit the LSA (Type 1) to the DR by (the BDR listens and retains a relationship with all the routers passually), the DR will publish the event to all neighboring routers on the common broadcasting network LSA. The DR will then announce the event (Type 2) The receipt is then accepted by all routers with an ACK packet and each router will have a synchronized LSDB copy.

The DR and BDR facts
1. These functions are not preemptive, whether a system is a DR or BDR it is subject to the following events:

Set Priority to 0c. Restart router d. Restart router phase of OSPF. Unplug cable from port. Restart the router process (clear network ospf);

2. The DR router is the first to boot, start processes in OSPF and go past the 40sec wait timer and send a hi packet to the DR before another router claims the DR job. 2. In the following 8th line, the waiting timer is visible.

Ip ospf interface R1 x#show
The line protocol Fastethernet0/0 is ready Internet Address 192.168.x.1/24, Area 0 Process ID 1, Router ID, BROADCAST Network Type, Cost: 10, Internet address: Conveyance 1 sec delay, State DR, priority 1 Designated router (ID) Backup Designated router (ID) Programmed timer cycles, interface address Interface address 192.168.3. Hi 10, Dead 40, Wait 40, Retransmission 5

3. Only one LAN section can be a DR for a router. 4. Set the DR to 255 by prioritizing the router. 5. Set the BDR to 250 prior to the router 6. Set the other routers Priority 1 to no routers. Don’t set them to 0 so, should you lose the Router Priority 0 routers with the DR and BDR, the routers would never become totally attached neighbors.

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