OSPF Flashcards
What are the criteria for DR / BDR election?
Priority, Highest RID
With what priority does a router not participate in the DR / BDR election?
0
OSPF multicast addresses?
224.0.0.5 All routers, 224.0.0.6 DR routers
What are the OSPF timers for broadcast and point-to-point networks? (both use the same timers)
hello 10, dead 40
Does OSPF support keys with lifetime?
False
What are the OSPF timers for NBMA networks, PMPe PMP NBMA?
30 120
What is the only network type where dynamic neighbor discovery does not occur?
NBMA
What are the only two network types that require DR/BDR?
Broadcast and Non-Broadcast Multi-Access, both multi-access
Which LSA is created by the DR?
Type 2 network, sh ip ospf database network
Which command allows viewing type 3 LSA?
show ip ospf database summary
Which command to view type 5 and type 4 LSAs?
show ip ospf database external, show ip ospf database asbr-summary
Neighbor in Attempt state?
Neighbor defined manually
What is the neighbor state when the first hello is received but the own RID is not yet listed?
init
What is the neighbor state when the hello is received and the own RID is listed?
2way
In which state does the master and slave negotiation occur?
exstart
In which state does the DDP exchange occur?
exchange
DDP is exchanged only for information between DROTHERS
False
Describe what happens in a broadcast network when a DROther’s link changes
The DROTHER originates LSA 1 for the DR, DR propagates via DDP to the DROTHERS, The DROTHERS request it from the DR via LSR, The DR delivers via LSU, The DROTHERS confirm via LSACK
What is the reflood period for LSAs?
30 minutes
What is the maximum ECMP path supported?
4 paths, modern IOS 16 to 32
Which LSAs cause SPF recalculation?
1 and 2
How to filter LSA 3 so that it does not enter area 0?
area 0 filter-list prefix-list FILTRO_OSPF in
How to filter OSPF routes so they do not enter the RIB?
router ospf 12, area 3 filter-list prefix DENY-OSPF in, ip prefix-list DENY-OSPF: 2 entries, seq 5 deny 12.0.255.23/32, seq 10 permit 0.0.0.0/0 le 32
What are the possibilities for route filtering?
Summary of filtering possibilities: Filter type 3 LSAs in ABRs, Filter type 5 LSAs in ASBRs, Filter routes to be installed in the local routing table
What metric will be assigned to a summarized route?
The best metric among the subordinate routes
What are the ways to generate a default route in OSPF?
area range 0.0.0.0 0.0.0.0 or summary address (ASBRs), Command default-information originate
Which type of special area does not receive a default route by default?
Not So Stub
Which LSAs are allowed in a Stub area?
1, 2, and 3 + default route via 3
Which LSAs are allowed in a Not So Stub Area?
1, 2, 3, and 7 (without default route)
Which LSAs are allowed in a Totally Stub Area?
1, 2 + default route via 3
Which LSAs are allowed in a Totally Not So Stub Area?
1, 2, and 7 + default route
Consider the topology: R1 R2 R3 R4. How should the virtual link be configured?
In R2 create a virtual link to the RID of R3 and vice versa, the transit area 1 must be referenced, in OSPFv3 this is done the same way but within the IPv6 unicast address family
In which network types does the next hop change occur?
In point-to-multipoint
In which network types must hellos be sent via unicast?
All non-broadcast, but why?
In which network types does the router announce the interface IP as /32?
In PMP and PMP NB and loopback
What is the AD for a summarized route in an ASBR?
254
What is the AD for a summarized route in an ABR?
110
Area x filter-list prefix-list in or out. The above command applies to which type of LSA?
Type 3
The filter list command in the in direction filters LSA entering the area
True
The filter list command in the out direction filters LSA entering the area
False
External routes are not filtered in ABRs due to the flooding scope of type 5 LSAs being the entire domain
True, filtering must be done in the ASBR
