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121 Cards in this Set
- Front
- Back
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ASBR
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Connects to different domain
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ABR
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Connects different areas
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Backbone
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At least one interface in Area 0
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Internal
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All interfaces in same area
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Type 1 Flood
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Entire Area
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Type 2 Flood
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Entire Area
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Type 3 Flood
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Entire AS
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Type 5 Flood
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Entire AS
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Type 6 Flood
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Entire AS
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LSA Type 1
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Router
Route links and state Flooded in the area of orig. |
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LSA Type 2
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Network
Generated by DR Lists all attached routers flooded in the area of orig. |
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LSA Type 3
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Network Summary
Generated by ABRs set into an area to advertise prefixes in other areas flooded through the AS |
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LSA Type 4
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ASBR Summary
generated by ABRs advertises the ASBR flooded throughout the AS |
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LSA Type 5
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AS External
generated by the ASBR advertises external destination flooded throughout the AS |
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LSA Type 7
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NSSA External
generated by the ASBR in NSSA advertises external destination |
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Allows you to see LSA in the OSPF database
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show ip ospf database
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An OSPF router in area 0 that connects to another AS and Area
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Considered a backbone router, ABR, and ASBR
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What router in an OSPF AS generates a Type 2 LSA
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DR
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What router in an OSPF AS generates a Type 5 LSA
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ASBR
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What type of area do you have in OSPF if you note Type 7 LSAs in use?
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NSSA
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Backbone Area
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Area 0
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Backbone Area Truths
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All inter-area traffic passes through the backbone
The backbone summarizes each area to each other area The area must be labeled 0 or 0.0.0.0 |
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What connects one OSPF AS to another OSPF AS or an Area that does not connect directly to Area 0?
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Virtual Link
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Stub Area
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Blocks type 4,5 (external types)
receives 1 type 3 default route from ABR to reach external and internal |
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Stub Area restrictions
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No Virtual Links permitted in or through area
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Totally Stubby
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Allows 1,2 from ABR
Blocks 3, 4, 5 |
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Not so stubby
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(ASBR)External routes propagated as type 7 to ABR
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Command for summarization from one area to another
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area range
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Summarization of external prefixes
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summary-address
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Main reason to summarize in OSPF
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To reduce the convergence domain size
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OSPF Algorithm
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Dijkstra Shortest path first
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OSPF P2P Link Adjacency
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P2P links - neighbors become fully adjacent
Occurs through exchanges of hello packets Once adjacent LSDB synched DROTHERS maintain partial relationship with each other |
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OSPF LAN Adjacency
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LAN - all routers form adjacency with DR and BDR
Occurs through exchanges of hello packets Once adjacent LSDB synched |
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OSPF P2P Link Adjacency
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No DR / BDR
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OSPF LAN Adjacency
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DR / BDR
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DR / BDR election
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Highest IP address or Highest Priority value
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DR / BDR priority value
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default is 1, non-preemptive
set to 0 to disallow router to become DR |
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OSPF NBMA Adjacency
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DR / BDR
Manual neighbor config (unicast) |
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NBMA
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Non-Broadcast Multi-Access
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DR
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Designated Router
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BDR
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Backup Designated Router
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OSPF P2MP Adjacency
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No DR/BDR
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OSPF P2MP Non-Broadcast Adjacency
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No DR/BDR
Manual neighbor config (unicast) |
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True or false there is a DR in an NBMA network type
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True
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True or false setting a higher priority on a device does not preempt the existing DR
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True
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OSPF Graceful Restart
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Also known as NSF or NSR
Stabilizes the peer devices as well |
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On dual proc systems, its the ability to continue forwarding traffic while restarting control plane of the second processor
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OSPF Graceful restart
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Graceful restart
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Also available for IS-IS, EIGRP, LDP, and BGP
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OSPF Graceful restart peers
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They need to be able to understand the graceful restart messaging
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What does a device use to forward traffic during a restart if it is capable of OSPF Graceful Restart?
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Hardware-Based forwarding
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OSPF Neighbor list empty
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Not properly configured on interfaces
Layer 1 or 2 issue Passive interface Access list block error in layer 3 interface config hello or dead time mismatch auth config error area id mismatch stub flag mismatch secondary IP addressing issue incorrect network type config |
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OSPF Stuck in ATTEMPT state
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misconfigured neighbor statement
unicast non-functional in NBMA environment |
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OSPF Stuck in INIT state
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Hellos being blocked in one direction
Multicast nonfunctional on one side Authentication only on one side Broadcast keyword missing from map command |
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OSPF Stuck in TWO-WAY State
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Priority of 0 on all routers
neighbor stuck in EXSTART mismatched MTU Duplicated Router IDs Broken unicast connectivity |
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OSPF Stuck in LOADING State
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Mismatched MTU
Corrupted link-state request |
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Name two network types you might configure in OSPF over frame relay that do not use a DR
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P2P and P2MP
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OSPF Version 2 RFC
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2328
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OSPF Multicast address (All SPF)
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224.0.0.5
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OSPF Multicast address (All DR)
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224.0.0.6
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State DOWN
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This is the first OSPF neighbor state. It means that no information (hellos) has been received from this neighbor, but hello packets can still be sent to the neighbor in this state.
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OSPF Neighbor State Attempt
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This state is only valid for manually configured neighbors in an NBMA environment. In Attempt state, the router sends unicast hello packets every poll interval to the neighbor, from which hellos have not been received within the dead interval
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OSPF Neighbor State Init
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This state specifies that the router has received a hello packet from its neighbor, but the receiving router's ID was not included in the hello packet.
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OSPF Neighbor State 2-Way
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This state designates that bi-directional communication has been established between two routers. Bi-directional means that each router has seen the other's hello packet.
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OSPF Neighbor State Exstart
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In this state, the routers and their DR and BDR establish a master-slave relationship and choose the initial sequence number for adjacency formation.
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OSPF Neighbor State Exchange
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In the exchange state, OSPF routers exchange database descriptor (DBD) packets.
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OSPF Neighbor State Loading
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In this state, the actual exchange of link state information occurs.
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OSPF Neighbor State FULL
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In this state, routers are fully adjacent with each other. All the router and network LSAs are exchanged and the routers' databases are fully synchronized.
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configure ospf priority
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interface sub-config mode
ip ospf priority 1 |
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Routing between AS's
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BGP
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BGP Features
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Reliable updates
Triggered updates Rich metrics Extremely scalable |
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True or false BGP discovers neighbors
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False, BGP requires manual neighbor configuration
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BGP uses TCP port #
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179
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This command is used for Internal BGP and external BGP peerings
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neighbor remote-as
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Assumed to be directly connected
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eBGP
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Use this command when eBGP neighbors are not directly connected
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neighbor ebgp-multihop
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This command is used to advertise prefixes in BGP
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network
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True or false the prefix must be in the routing table for the BGP network command to advertise the prefix
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True
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iBGP split horizon
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An iBGP learned route will not be forwarded on to another iBGP peer.
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Ways around BGP Split horizon
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route reflector
confederations full mesh |
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DUAL
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Diffusing Update Algorithm
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True or False Auto-summary is enabled by default with EIGRP
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True
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The 5 EIGRP Metrics
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Bandwidth (weakest link)
Delay (sum for path) Reliability Load MTU |
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Real metrics used by EIGRP
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Bandwidth
Delay |
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CIR
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Committed Information Rate
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K value
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constant value, coordinate the use of metrics in the metric formula
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true or false K values must match between your EIGRP speakers
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True
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True or false reliability and load are not considered by default in EIGRP
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True
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True or false it is the weakest link bandwidth that is considered in the calculation in EIGRP
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True
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True or False MTU does not have a corresponding K Value
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True
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What is feasible distance?
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the cost between the local router and the destination prefix
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What does the feasible distance consist of?
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the cost to the next hop, added to the cost that the next hop is advertising to the local router (Advertised Distance)
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What is a Successor?
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the best (lowest cost) route to a destination
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What is a feasible successor?
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The second best route
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What is required of Feasible successors next hop? Feasibility condition..Loop prevention measure DUAL takes
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next hop must have Advertised Distance less than the current FD of the successor
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Another name for advertised distance is
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Reported Distance
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Successor
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The best path to the destination
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FD
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cost from local device to destination
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Feasible successor
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the second best path
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Advertised distance (AD)
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cost from the next hop to destination
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Passive
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network available
State seen in show ip eigrp topology |
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Active
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network unavailable
State seen in show ip eigrp topology |
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Update
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network is being updated
State seen in show ip eigrp topology |
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Query
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Outstanding query wait for ACK
State seen in show ip eigrp topology |
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Reply
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generating a reply to a Query
State seen in show ip eigrp topology |
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SIA (Stuck in active)
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convergence problem
State seen in show ip eigrp topology |
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Describe the rule for the selection of a Feasible Successor route in EIGRP and why does the condition exist?
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The feasibility condition states that the advertised distance (AD) of a potential Feasible successor route must be less than the Feasible Distance (FD) of the current successor route. This is a loop prevention mechanism.
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Use of MTU in the EIGRP metric calculation...
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MTU is a tiebreaker and is not actually used in the calculation of the EIGRP metric
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True or false EIGRP is plug and play
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False
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EIGRP passive routes are better than active routes true or false
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True
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In the EIGRP topology table, what is the ( x/x )
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(FD/AD)
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describe two methods of scoping queries of EIGRP
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Queries can be scoped using summarization or the EIGRP stub feature
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Describe the EIGRP SIA problem
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As EIGRP router sends a query becuase a route has been removed from the EIGRP topology table and there is no feasible successor route. If the query is not responded to by a neighbor within a certain time limit, the neighbor relationship between the devices resets
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PBR
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Policy Based routing
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PBR is built using what
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Route map
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PBR traffic is matched based on
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Access list protocol or app
Access list source and/or destination Layer 3 packet length |
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What type of behaviors can be set by PBR
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Next hop
output interface default next hop or interface |
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PBR only affects traffic...
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through the router
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benefits for multi-area OSPF
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reduction in SPF calculations
Memory and CPU utilization reduction in routing table size |
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Valid reasons an OSPF neighborship might not form:
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timer mismatch
stub flag setting MTU mismatch |
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highest to lowest preference for OSPF route selection process:
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intra-area
inter-area External type 1 External type 2 |
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two modes for router under IETF NSF
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restarting mode
helper mode |
