Flashcards
OSPF
Cards in this deck (38)
- 1How many LSAs?11
- 2What is the LSDB?Link State Database, the neighbors, topology and routes
- 3What is an LSU?Link State Update, can contain LSAs
- 4What is the rule of thumb of max routers in an AS?50
- 5What is an LSALink state advertisement
- 6what is a Backbone router?Any router with an interface in area 0
- 7Whats an ABR?Area Border Router, sits on the edge of an area
- 8What is an internal routerany router in an Area that is not on the edge of that area
- 9What multicast address does the DR and BDR listen to?224.0.0.6
they send updates out
224.0.0.5 - 10How does OSPF relate to TCP/UPDWorks on top of IP (protocol #89) but is independent of transport layer protocols like TCP/UPD
- 11When does OSPF send updates?When a neighbor first comes up, sends full table, then just partial update during when new link comes up
- 12What is the metric OSPF uses?based on the cumulative costs of a
- 13what are the 5 general steps of ospf?1. Establish neighbor adjacencies
2. Exchange link-state advertisements
3. Build the topology table
4. Execute the SPF algorithm
5. Build the routing table - 14What are the 5 message types of OSFP?Type 1: Hello packet
Type 2: Database Description (DBD) packet
Type 3: Link-State Request (LSR) packet
Type 4: Link-State Update (LSU) packet
Type 5: Link-State Acknowledgment (LSAck) packet - 15What are type 1 LSAs and who sends them?Router, all routers send them
- 16What are the only 2 routers types that can send summaries?ABRs and ASBRs
you can only summarize on the boarders!!!! - 17default hello timer of ospf?10 seconds on broadcast and point to point
30 seconds on non-broadcast and multipoint - 18what attributes must be the same for an adjacency to form?hello/dead timers
netmasks
area id
authentication passwords - 19default dead timer40 seconds
- 20who sends DBD packet first?the Master. Router with higher priority sends first
- 21What is the DataBase Description packet? DBD?It's a cliff notes version of all the routes the router knows about. If the other router sees that it is missing some, it sends LSR to request missing routes
- 22when 2 routers are compatible but they don't continue to form adjacency, what state do they remain in?2-way
- 23what kind of topology change triggers SPF recalculation?intra-area topology change
- 24do type 3 LSAs trigger SPF recalculation?no, the input information for best path remains the same.
- 25what is the ospf cost formula?reference bandwidth divided by interface bandwidth
- 26What is the default ospf cost for Fastethernet, gigethernet, 10gigethernet?1....
- 27how can you influence the cost of a single interface?with the "bandwidth " command
- 28what are type 3 LSAs?intER-area route advertisements sent from ABRs
- 29How are ABRs and ASBRs different?An ABR is just on the boarder of an area within a single AS. An ASBR sits on the edge of the AS and connects to another AS outside the company's network
- 30what is the difference between intRA area and intER are?intRA is within an area
intER is between areas - 31Why do we cut OSPF up into multiple areas?to cut down on route updates and associated traffic, also to enable summation
- 32Where does route summarization happen in OSPF?only on the ABRs and ASBRs, not in internal routers
- 33What is a virtual link?like a trick to make an area think it's connected to area 0 when it's not, via a tunnel through a transit area.
- 34What is a STUB area?doesn't accept routes external to the AS. If need to route to address outside AS, gotta use default route. No ASBRs allowed in stub area
- 35what is a totally stubby area?cisco proprietary area, doesn't accept any routes places outside the AS OR from other areas internal to the AS.
- 36what is a NotSoStubbyArea?A stub area that allows injection of external routes in a limited way. (type 7 LSA)
- 37what is so big about OSPFv3?IPv6 support
- 38—
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- CWNA Networking (300-101 CCNP ROUTE Exam Topics) Flashcards on OSPF, created by Dustin Sanders on 11/06/2017.
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- Dustin Sanders
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