Chap 6 - IP Routing Essentials Flashcards
What is a network of interconnected routers and systems under a common administration called?
Autonomous System or Routing Domain
What are the 5 most common routing protocols found on most routing platforms?
- RIPv2
- EIGRP
- OSPF
- IS-IS
- BGP
What is the difference between an IGP and an EGP?
- IGPs are optimized for routing within an AS
- EGPs are optimized for routing between Ass
What is BGP called when it is used within an autonomous system?
Interior BGP
What is BGP called when it is used to route between autonomous systems?
Exterior BGP
What does a Distance Vector routing protocol base its route computation on?
- Distance (number of hops)
- Vector (the local interface it uses to send the packet on its way)
What are 2 advantages of a Distance Vector routing protocol?
- Requires less CPU and memory
- Can run on low-end routers
What is the name of an enhanced Distance Vector algorithm used to calculate the shortest path to a destination?
Diffusing Update Algorithm (DUAL)
Which routing protocol uses DUAL?
EIGRP
Which routing protocol uses Bellman-Ford?
RIP or other Distance Vector protocols
What are 5 enhancements introduced by DUAL?
- Rapid Convergence
- Sends updates only when there’s a change
- Uses Hellos and forms Neighborships
- Uses bandwidth, delay, reliability, load and MTU
- can Load Balance across equal or un-equal cost links
Why is EIGRP called a Hybrid Routing Protocol?
Because it has characteristics of both Distance Vector and Link State routing protocols
By default what does EIGRP advertise?
- Total path delay
- Minimum bandwidth
What are 2 Link State routing protocols?
- OSPF
- IS-IS
What are OSPF advertisements called?
Link State Advertisements (LSAs)
What are IS-IS advertisements called?
Link State Packets (LSPs)
Where does an OSPF router store its LSAs?
Link State Database (LSDB)
What calculation method does OSPF use?
Djikstra Shortest Path First algorithm
What does OSPF use to enable features for Service Providers?
Opaque LSAs
What does IS-IS use to enable features for Service Providers?
TLVs (type, length, value)
What disadvantage is there to using a link state routing protocol?
They use more CPU and memory.
What 2 advantages are there to using a link state routing protocol rather than a distance vector routing protocol?
- Link State protocols make better routing decisions
- Link State protocols are less prone to routing loops
What type of routing protocol is BGP?
Path Vector Algorithm
What does BGP use to compute routes?
BGP Path Attributes
What are the 13 BGP Path Attributes?
- Weight
- Local Pref
- Locally originated
- AIGP
- Shortest AS_PATH
- Origin Type
- Lowest MED
- EBGP over IBGP
- Lowest IGP Next Hop
- If eBGP then oldest route
- Peer with lowest router-id
- Minimum cluster length
- Peer with the Lowest Neighbor IP address
How does a Path Vector Algorithm prevent loops?
If it receives an advertisement that already includes its AS in it drops the advertisement
What 3 steps does a router take to identify the path a packet should take?
- Routing table populated with routes presented from routing protocol processes
- FIB is programed through the routing table
- Forwarding decision is a function of the FIB and results from calculations performed in the RIB
What 3 components determine Path Selection?
- Prefix Length
- Administrative Distance
- Metrics
What is the forwarding decision a function of?
- The FIB
- Calculations done in the routing table
How is the RIB calculated?
- Administrative Distance
- Metric
What is ECMP?
Equal Cost Multipathing
What are 2 cases when static routes are needed?
- Dynamic routing protocols can’t be used due to limited CPU and/or memory
- Routes learned from Dynamic Routing Protocol needs to be superseded.
What are 3 types of static routes?
- Directly attached static routes
- Recursive static routes
- Fully specified static routes
If a directly attached static route has been configured and the interface goes down what happens to the route?
It is removed from the RIB.
What 3 advantages does using VRFs with IP routing have over Layer 2 technology?
- improved convergence times
- dynamic traffic load sharing
- the ability to use ping and traceroute troubleshooting tools
Display the routes in a VRF.
show ip route vrf (vrf_name)
What 4 pieces of information does every routing protocol present to the RIB for insertion?
- Destination network
- Next-hop IP address
- AD
- Metric values
What are the 3 factors are used by the RIB when deciding to accept or reject a route?
- If the route does not exist in the RIB then accept the route
- If the route exists and its AD is lower than that of the new route then the new route is rejected.
- If the route exists and its AD is higher than that of the new route then the new route is accepted and the old route is removed
When configuring a static route in IPV6 when would you need to use a fully specified static route?
If the next hop address is a link local address
What is the name of a distance vector algorithm that is not enhanced?
Bellman-Ford
