As a CCNA / CCNP candidate you are expected to understand the purpose and function of the OSPF protocol. The CCNA / CCNP’s exam will ask of you to determine the purpose of the DR and BDR along with the election procedure.

OSPF Designated Router and Backup Designated Router elections

OSPF routing algorithm is CPU intensive. Each and every time the OSPF process runs the shortest path first algorithm it will have an impact on the router. In a point to point network OSPF events are limited to the periodic Hello packet (Default 10secs on a PPP, HDLC, 30sec Frame Relay NBMA), 30 mins for each route entry in the Link state database and triggered events.

In a Multi-access broadcast network where routers are connected to a common broadcast segment i.e many routers in one vlan) all routers would need to create an adjacency with all other routers in the same broadcast domain. Also event which causes an LSA to be generated would require the advertising router to create one LSA to be multicasted to all neighbours. The more routers there are in the broadcast multicast network the more adjacencies would be required. Two routers require the following number of adjacencies: 2(2-1) / 2 = 1

Four routers require the following number of adjacencies: 4(4-1)/2=6

Ten routers require the following number of adjacencies: 10(10-1)/2=45

Note: DR’s and BDR’s are not elected on point-to-point links because there can be only one adjacency and the point of electing the DR and BDR is for efficiency. The more routers you have on a segment will increase the number of adjacencies consume more bandwidth and use more processing power on the routers. We need to reduce the amount of work which each router has to do on the next by electing one router as a Designated Router which all other routers with form adjacencies with. When you use a Designated Router in your Multiaccess broadcast network the number of adjacencies is reduced along with the reduction in processing and bandwidth. All routers will form full adjacencies with the Designated router, when you run the command on a cisco router which is not the DR: R1#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

192.168.1.3 1 FULL/DR 00:00:39 192.168.1.3 Ethernet0/0

You will see that your router has formed a “FULL” neighbour adjacency with the DR and the output also defines which neighbor is the DR. The router ID of the neighbour in the output above is 192.168.1.3 and that this neighbour is the DR

Any events which occur are advertised to the DR using the Multicast address of 224.0.0.6

When the DR advertises any events to the Non-DR devices it is done using the address of 224.0.0.5

Designated and Backup Designated Router Election:

The DR is elected based on the router with the highest router priority. The default router priority is 1, the range is 0 to 255. Setting the router priority to 0 means the interface cannot participate in any DR or BDR election. If you set a current DR’s r current BDR’s router priority to 0 it will relinquish the role immediately. Routers which are not elected either as DR or BDR still form neighbor adjacencies, although they will not exchange any routing information between each other, only hellos are exchanged and these are sent to multicast address of 224.0.0.5

Despite the name “router priority” it is in fact a priority which s set on an interface level as follows:

R1(conf)#interface fastethernet 0/0 R1(conf-if)#ip ospf priority 1

In the event that two or more interfaces sharing a common broadcast domain have the same router priority the OSPF router ID is used as a tie-breaker. The election process is as follows:

1. To participate in the election any router with its OSPF priority set between 1-255 can attempt to become DR by putting its own Router ID into the DR field of its sent hellos. You can view the election process by running the command “debug ip ospf adj”, the elections occurs during the 2-way process. 2. Each and every router in the common broadcast domain examine the received Hellos, looking at other routers’ priority settings 3. If a received Hello from another router has a better router priority then that router stops claiming to be DR and asserts that the better candidate should be the DR by placing the Router ID of the DR into the DR field of it’s Hello packets. Therefore the first criteria for better is a router with the highest priority 4. If the Router Priorities are identical, the router with the higher RID is chosen as the DR 5. The with the next highest priority or next highest Router ID in the case hat there is a tie in the value of the Router Priority becomes the BDR, (Backup Designated Router). 6. If a new router comes onto the network after the election of the DR and/or BDR, or if any existing router improves it’s priority it will not be able to pre-empt the existing DR or even the BDR, remember that DR and BDR roles are non-preemptive. 7. If the DR fails the existing BDR will take over as DR and another election is held for the BDR. 8. If the previous DR comes back online it will not be able to resume it’s previous role.

When a router which is neither the DR or the BDR needs to advertise an event to its neighbors on the common broadcast network it will send the LSA (Type 1) to the DR using the address of 224.0.0.6 (The BDR listens passively to this exchange and maintains a relationship with all the routers), the DR will then advertise the event to all adjacent routers on the common broadcast network LSA (Type 2) All routers will then acknowledge the receipt with an ACK packet ensures that each has a synchronized copy of the LSDB.

Facts about the DR and BDR

1. These roles are not pre-emptive, once a device is a DR or BDR the only events that can cause it to give up the roles are as follows:

a. Shut the interface down b. Set Priority to 0 c. Restart the router d. Restart the OSPF router process (clear ip ospf process) e. Unplug the cable from the interface

2. The router which becomes the DR is the first one which boots up, starts it’s OSPF processes and gets past the 40sec wait timer, before it sees another router sending it’s own hello packet claiming the DR role. The wait timer can be seen in the output below, 8th line down.

R1_x#show ip ospf interface

Fastethernet0/0 is up, line protocol is up Internet Address 192.168.x.1/24, Area 0 Process ID 1, Router ID 192.168.3.1, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State DR, Priority 1 Designated Router (ID) 192.168.3.1, Interface address 192.168.3.1 Backup Designated router (ID) 192.168.3.2, Interface address 192.168.3.2 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

3. A router should only be a DR for one LAN segment. 4. Set the DR by setting it’s Router priority to 255. 5. Set the BDR by setting it’s Router Priority to 250 6. Set all other routers Router Priority to 1, never set them to 0 because in the event that you lose both the DR and BDR the routers with the Router Priority of 0 will never become fully adjacent neighbors and in turn will never exchange routing information

American audiences love sequels. If you loved or hated the Mueller report, you will love or hate the congressional sequel as public impeachment hearings begin November 13. Donald Trump appeared to get away with “in your face” election interference in 2016. Can he do it again in 2020? If so, will he go for a third or fourth sequel?

But there’s more. Trump’s episodes are a repeat of Nixon’s dramas in 1968 and 1972. President Johnson and top officials around him knew that Nixon got away with interfering in foreign policy in 1968 and thus won election through international dirty tricks. Although unknown at the time, the Watergate break-in was a sequel in domestic policy to Nixon’s successful interference of 1968.

Even as the outcome of the unfolding impeachment drama remains uncertain, three historical lessons can be seen although their outcomes can’t be predicted at this time. Contrary to what you hear, history does not repeat itself. But some themes and patterns recur, taking unexpected shapes that raise new dangers and possibilities as in the case of these three lessons.

Lesson One: Parallelism. Nixon was caught during his second term for illegally meddling in an election he was sure to win. He had gotten away with illegal meddling in the 1968 election as President Johnson sealed the evidence out of concern for national security. Donald Trump meddled in the 2016 campaign in front of television cameras. The investigation into his actions were kept secret even as investigations of his opponent impacted the campaign. Trump damaged the effectiveness of the Mueller Report by attacking it for two years then having his Attorney General undermine it as it was released. Despite evidence that should have led to impeachment, it appeared that meddling during the 2016 campaign might not prevent Trump’s re-election.

The parallel with Nixon becomes clear after the Mueller Report. Needing still more Russian help to win re-election, Trump began to drum up investigations into his most feared opponent in 2020 by using military aid funded by congress to extort the president of Ukraine. This was not done before cameras but in the presence of seasoned diplomatic professionals who understood the dangers to our national security.

Seeming to have escaped meddling for a first term, as Nixon had also escaped, Trump was caught doing the same thing for a second term. The whistleblower’s complaint had the effect of the botched Watergate break-in. Both events brought into the light events meant to happen in secret. Investigations then led to conscience-stricken individuals standing before cameras exposing presidential underhandedness to the world.

Lesson Two: Predictable versus Unpredictable Outcome. Media commentators and political scientists are behaving more like football announcers when they focus on political gamesmanship to predict the outcome of this impeachment process. The outcome of the Bill Clinton impeachment became clear when Senate Democrats stood behind him, agreeing with most of the American people that he had done wrong but should not have been impeached. The outcome for Nixon, however, was not predictable. He was not impeached or put on trial because support collapsed to the point that he resigned rather than endure the process. Therefore, if impeaching Trump fails, it will happen predictably as Senate Republicans follow Mitch McConnell and hold the line. If impeachment succeeds, it will most likely take a course not being predicted at this time and will demonstrate the skill of Nancy Pelosi for negotiating impossible situations.

This impeachment process depends on the contest between Mitch McConnell and Nancy Pelosi. It is possibly the last battle of the war between them since the Affordable Care Act (ACA). McConnell held the Republican line in the Senate when the ACA passed with a 60-vote Democratic majority. Soon thereafter, Democrats lost one of those seats and it appeared certain the House would never accept the Senate version. That is when Pelosi did the impossible, proving herself to be a closer when it counts – even when it meant losing the majority in the House. McConnell then used the ACA to defeat Democrats for four consecutive congressional elections. But elimination of the ACA only became possible after the victory of 2016 with the victory of Trump. That’s when public opinion turned as it became clear there was no Republican alternative to the benefits millions of people would lose.Mitch McConnell appears to have the upper hand if impeachment moves to trial in the Senate. No one doubts he intends to stand by the party rather than the country – he already committed to that choice in the election of 2016 when he refused to support President Obama’s actions against Russian interference.

However, Nancy Pelosi gets to manage the process before it goes to the Senate. She has an impressive record of winning when she commits to fights and should not be underestimated. She has also demonstrated her commitment to country more than party. If her strategy leads to successfully bringing down Donald Trump, it will almost certainly follow a route no one can predict as public hearings begin.

Lesson Three: Russia and China. Nixon meddled in two elections while we were in a war in Vietnam. Our enemy was North Vietnam, but we knew they were a proxy for China and Russia. Nixon was also extremely skillful in reorienting national policies toward China and Russia in ways that clearly promoted world peace and did not undermine our international alliances.

Any true disciple of Nixon Republicanism must be shocked that the Nixon revenge squad of Roger Ailes, Paul Manafort, and Roger Stone used Russian help to elect Donald Trump. The meddling in Ukraine also helps Russia while demonstrating to other allies that we can’t be trusted.

Eisenhower, Nixon, and Reagan would roll over in their graves (if such a thing were possible) at the prospect of a Republican president single-handedly cow-towing to Russia, attacking our European allies, undermining the confidence of South Korea and Japan, and sending our farmers into recession through a trade war with China that has permanently undermined agricultural supply chains. These achievements of the first term will be followed by greater catastrophes if current election meddling brings a second Trump presidential term.

Conclusion. Richard Nixon undermined peace efforts in Vietnam as part of running for president in 1968. Lyndon Johnson hid that deed from the public out of concern for national security. Nixon meddled in the election of 1972, was caught, and had to resign to escape impeachment. Three Nixon followers out for revenge (Roger Ailes, Paul Manafort, and Roger Stone) helped Donald Trump win the election of 2016 with Russian support. Trump’s opponent was known to be under FBI investigation but news of a more serious investigation into Trump was kept secret. The FBI investigation resulted in the work of Special Prosecutor Robert Mueller which was successfully obstructed. Mueller’s results played by the rules in a way that seemed to reward obstruction. With the help of a compliant Attorney General, it looked as if Trump had escaped. Then came news of a whistleblower, like the surprising news of the Watergate break-in. This led to a series of professionals telling the truth to congress and prompted an impeachment inquiry.

Like Nixon, Trump was caught with smoking gun in his hand. Both got away with murder the first time. Will Trump escape the second time?

The answer depends on the American people and Nancy Pelosi. The public is about to hear the truth. Will we recognize it and demand removal of this president? If impeachment succeeds, it will happen because of the insight and integrity of Nancy Pelosi and her team. And the outcome will be something none of us can predict as the public hearings begin.

References on Nixon’s 1968 Election Interference:

Peter Baker, “Nixon Tried to Spoil Johnson’s Vietnam Peace Talks in ’68, Notes Show,” The New York Times (January 2, 2017), https://www.nytimes.com/2017/01/02/us/politics/nixon-tried-to-spoil-johnsons-vietnam-peace-talks-in-68-notes-show.html.

John A. Farrell, “When a Candidate Conspired With a Foreign Power to Win An Election,” Politico Magazine (August 6, 2017), https://www.politico.com/magazine/story/2017/08/06/nixon-vietnam-candidate-conspired-with-foreign-power-win-election-215461.

Robert Johnson, “Did Nixon Commit Treason in 1968? What The New LBJ Tapes Reveal,” History News Network, https://historynewsnetwork.org/article/60446.

Charles Wheeler, “The Lyndon Johnson tapes: Richard Nixon’s ‘treason’,” BBC News Magazine (March 22, 2013), https://www.bbc.com/news/magazine-21768668.