ICND2 Section 3 - IPv4 Routing Protocols Flashcards
In OSPF, what’s the difference between the init and 2way states?
Init 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.
2way is attained when the router receiving the hello packet sees its own Router ID within the received hello packet’s neighbor field.
What are the 8 states of OSPF neighbors?
Down Attempt Init 2way ExStart Exchange Loading Full
In what type of environment is an OSPF state of Attempt valid?
NBMA only
What kind of packet is used during the ExStart and Exchange phases?
DDP
What does DDP stand for?
Database Descriptor Packet
What kind of packets are used during the Loading phase?
LSU
What does an LSU contain?
One or several LSA’s
What information is in a Network LSA?
the DR on a broadcast segment lists which routers are joined together by the segment. The LSID of the type 2 LSA is the IP interface address of the DR.
What information is in a Summary LSA?
Information about subnets in other areas
Subnet ID,
mask,
RID of ABR that advertises the LSA
In what OSPF phase do neighbors pass each other their LSA’s?
Loading
What are the 2 primary timers in OSPF?
Hello
Dead Interval
What are the default settings for the OSPF hello and dead intervals on non-serial interfaces?
Hello = 10 seconds
Dead Interval = 4*(HelloInterval)
For DROthers, what is the maximum state that they reach with each other?
2way
List the first 3 OSPF LSAs
Router
Network
Summary
What info is in a Router LSA?
RID Directly connected interface info -network -mask -cost
What is the area scope of type 1 and 2 LSAs?
Intra-area only
What router type advertises type 3 LSAs, and what are they used for?
ABRs advertise them.
They are used for advertising networks from one area into another.
When an ABR floods a summary LSA, what is the advertising router set to?
Itself, so the ABR looks like the one that has all of the routes directly connected.
OSPF command to set the number of paths that will be used in ECMP
maximum-paths
How does route poisoning work?
A route that is no longer valid will be advertised with the max metric, to let all other routers know that it’s no longer available.
How does split horizon work?
Do not advertise routes out an interface which is the exit interface to get to said routes.
When does EIGRP send full and partial updates?
Full on neighbor adjacency
Partial as needed when network topology changes
What are the 2 primary timers for EIGRP?
Hello
Hold
What are the default values for the Hello and Hold timers in EIGRP?
Hello = 5 seconds Hold = 3xHello, or 15 seconds by default
What are EIGRP’s 2 primary metrics?
Bandwidth and Delay
What is the multicast address for EIGRP?
224.0.0.10
Does EIGRP ever flood updates periodically?
No, only during adjacency setup or topology changes
What are the 3 required and 1 optional attributes that must pass before an EIGRP adjacency will be established?
Required: 1. Same AS number 2. Same IP subnet 3. Matching K values Optional: 1. Authentication, if configured, must match.
What is the Feasible Distance in EIGRP?
The metric of an EIGRP route on the local router.
What is the Reported Distance in EIGRP?
The next-hop router’s best metric for a FD subnet
What algorithm is used by EIGRP
DUAL
What does DUAL stand for?
Diffusing Update ALgorithm
Does the EIGRP ASN need to match between neighbors?
Yes
Syntax to include interfaces into EIGRP
conf t
router eigrp
network \
What 5 attributes must match for OSPF neighbors to become adjacent?
- Same subnet
- Hold/dead timers
- Authentication
- Same area
- Same interface MTU
What 3 attributes must match for EIGRP neighbors to become adjacent?
- Same subnet
- Same ASN
- Matching K-values
