Ch 10: OSPF v3 Flashcards
OSPFv3 uses ___________ packet types for inter-router communication.
a. three
b. four
c. five
d. six
e. seven
C.
OSPFv3 uses five packet types for communication:
- hello
- database description
- link-state request
- link-state update
- link-state acknowledgment
These packet types have exactly same names and functions as the same packet types in OSPFv2.
The OSPFv3 hello packet uses the ___________ for the destination address.
- MAC address 00:C1:00:5C:00:FF
- MAC address E0:00:00:06:00:AA
- IP address 224.0.0.8
- IP address 224.0.0.10
- IPv6 address FF02::A
- IPv6 address FF02::5
- OSPFv3 uses link-local addresses for a majority of communication, but it uses the destination IPv6 address (FF02::5) for hello packets and link-state updates.
How do you enable OSPFv3 on an interface?
- Use the command network prefix/prefix-length under the OSPF process.
- Use the command network interface-id under the OSPF process.
- Use the command ospfv3 process-id ipv6 area area-id under the interface.
- Nothing. OSPFv3 is enabled on all IPv6 interfaces upon initialization of the OSPF process.
C. Enabling OSPFv3 requires the interface configuration command ospfv3 process-id ipv6 area area-id.
T/F: On a brand-new router installation, OSPFv3 requires only that an IPv6 link-local address be configured and that OSPFv3 be enabled on that interface to form an OSPFv3 neighborship with another router.
False. You need a router ID. This can be manually assigned with the command router-id router-id. Router ID can also be automatically set to an IPv4 address configured on a loopback or interface.
If not, the router ID is set to 0.0.0.0, and it will not be able to form a neighborship with another OSPFv3 router.
T/F: OSPFv3 support for IPv4 networks only requires that an IPv4 address be assigned to the interface and that the OSPFv3 process be initialized for IPv4.
False. OSPFv3 requires an IPv6 link-local address to establish neighborship to exchange IPv6 or IPv4 routes.
T/F: OSPFv3 supports IPv4 and IPv6 address families.
True.
Unlike IPv4, IPv6 supports both, backward compatible.
How is the IP prefix information carried in OSPFv3?
The IP prefix information is no longer present in the OSPF packet headers. Instead, it is carried as LSA payload information, making the protocol essentially address family independent, much like IS-IS.
OSPFv3 uses the term link instead of network because the SPT calculations are per link instead of per subnet.
T/F: OSPFv3 includes the same link-state type field that was used with OSPF and is also used to determine the flooding scope of LSA, as well as the handling of unknown LSA types.
False.
OSPFv3 includes a new link-state type field that is used to determine the flooding scope of LSA, as well as the handling of unknown LSA types.
T/F: The number of fields in the packet header has been increased to accomodate backward compatability with OSPF.
False.
OSPFv3 runs directly over IPv6, and the number of fields in the packet header has been reduced.
T/F: OSPFv3 will use the highest IPv4 address on a loopback or interface for the router ID if it is not set manually.
True.
OSPFv3 is backward-compatible with OSPF version 2. In OSPFv3 and OSPF version 2, the router uses the 32-bit IPv4 address to select the router ID for an OSPFv3 process.
If an IPv4 address exists when OSPFv3 is enabled on an interface, then that IPv4 address is used for the router ID. If more than one IPv4 address is available, a router ID is chosen using the same rules as for OSPF version 2.
If no IPv4 addresses are configured with the router-id command, the router selects a router ID automatically. Each router ID must be unique.
If no interfaces are configured with an IP then the router ID is 0.0.0.0 and does not form any adjacencies… epic fail.
T/F: Neighbor authentication has been removed from the OSPF protocol and is now performed through IPsec extension headers in the IPv6 packet.
True.
T/F: OSPFv3 allows for neighbor adjacency to form even if the two routers do not share a common subnet.
True.
OSPFv3 inter-router communication is handled by IPv6 link-local addressing. Neighbors are not automatically detected over non-broadcast multiple access (NBMA) interfaces. A neighbor must be manually specified using the link-local address.
IPv6 allows for multiple subnets to be assigned to a single interface, and OSPFv3 allows for neighbor adjacency to form even if the two routers do not share a common subnet.
T/F: In OSPFv3 neighbors are automatically detected over non-broadcast multiple access (NBMA) interfaces.
False.
OSPFv3 inter-router communication is handled by IPv6 link-local addressing. Neighbors are not automatically detected over non-broadcast multiple access (NBMA) interfaces. A neighbor must be manually specified using the link-local address. IPv6 allows for multiple subnets to be assigned to a single interface, and OSPFv3 allows for neighbor adjacency to form even if the two routers do not share a common subnet.
T/F: OSPFv3 inter-router communication is handled by IPv6 link-local addressing.
True.
OSPFv3 inter-router communication is handled by IPv6 link-local addressing. Neighbors are not automatically detected over non-broadcast multiple access (NBMA) interfaces. A neighbor must be manually specified using the link-local address. IPv6 allows for multiple subnets to be assigned to a single interface, and OSPFv3 allows for neighbor adjacency to form even if the two routers do not share a common subnet.
T/F: OSPFv3 packets include an instance ID field that may be used to manipulate which routers on a network segment are allowed to form adjacencies based on Address Family.
True.
Support of Address Families in OSPFv3:
OSPFv3 has a mechanism for supporting multiple address families (AFs). It maps an AF to an OSPFv3 instance using the Instance ID field in the OSPFv3 packet header. This approach is fairly simple and minimizes extensions to OSPFv3 for supporting multiple AFs.
T/F: OSPFv3 packets use protocol ID 88, and routers communicate with each other using the local interface’s IPv6 link-local address.
False and True.
OSPFv3 packets use protocol ID 89, and routers communicate with each other using the local interface’s IPv6 link-local address.
Which of the following is not correct:
- OSPFv3 modifies the structure of the router LSA (type 1), renames the network summary LSA to the interarea prefix LSA
- OSPFv3 renames the ASBR summary LSA to the intra-area router LSA.
- The principal difference is that the router LSA is only responsible for announcing interface parameters such as the interface type (point-to-point, broadcast, NBMA, point-to-multipoint, and virtual links) and metric (cost).
2 is not correct.
The OSPF link-state database information is organized and advertised differently in Version 3 than in Version 2.
- OSPFv3 modifies the structure of the router LSA (type 1), renames the network summary LSA to the interarea prefix LSA
- OSPFv3 renames the ASBR summary LSA to the interarea router LSA.
- The principal difference is that the router LSA is only responsible for announcing interface parameters such as the interface type (point-to-point, broadcast, NBMA, point-to-multipoint, and virtual links) and metric (cost).
How many packet types are used by OSPFv3?
OSPFv3 uses the same five packet types and logic as OSPFv2. Table 10-3 shows the name, address, and purpose of each of the five packets types.
Match up the OSPFv3 LSA types with their functions.
- Hello
- Database description
- Link-state request
- Link-state update
- Link-state acknowledgment
- Database information request
- Initial adjacency forming, in response to a link-state request, Database update
- Summarize database contents
- Initial adjacency forming, in response to a link-state update, Flooding acknowledgment
- Discover and maintain neighbors, Initial adjacency forming, immediate hello
1 - 5
2 - 3
3 - 1
4 - 2
5 - 4
What is the command to show OSPFv3 neighbors?
show ospfv3 ipv6 neighbor (IPv6 neighbors)
and
show ip ospf neighbor (IPv4 neighbors)
What is the command to show an OSPFv3 interface?
show ospfv3 interface [interface-id]
What is the command to show an OSPFv3 interface summary?
show ospfv3 interface brief
What is the command to view the routing table with OSPFv3?
show ipv6 route ospf
Intra-area routes are indicated with O, and interarea routes are indicated with OI.
Example 10-5 shows this command being executed on R1. The forwarding address for the routes is the link-local address of the neighboring router.
T/F: OSPFv3 no longer supports the ability to mark an interface as passive.
False.
OSPFv3 supports the ability to mark an interface as passive.
The command is placed under the OSPFv3 process or under the specific address family. Placing the command under the global process cascades the setting to both address families.
An interface is marked as being passive with the command passive-interface interface-id or globally with passive-interface default, and then the interface is marked as active with the command no passive-interface interface-id.
What is the command to verify the active/passive state of an interface?
The active/passive state of an interface is verified by examining the OSPFv3 interface status using the command show ospfv3 interface [interface-id] and searching for the Passive keyword. In Example 10-7, R1 confirms that the Gi0/3 interface is passive.
What is the OSPFv3 command for summarization and where is it applied?
Summarization involves the command area area-id range prefix/ prefix-length, which resides under the address family in the OSPFv3 process.
T/F: OSPFv3 supports the same OSPF network types as OSPFv2.
True.
OSPFv3 supports the same OSPF network types as OSPFv2.
Example 10-11 shows that R2’s Gi0/3 interface is set as a broadcast OSPF network type and is confirmed as being in a DR state.
What is the OSPFv3 command to change the network type?
The OSPFv3 network type is changed with the interface parameter command ospfv3 network {point-to-point | broadcast}.
Example 10-12 shows the interfaces associated with the 2001:DB8:0:23::/64 network being changed to point-to-point.
What are the steps to enable IPv4 in OSPFv3?
OSPFv3 supports multiple address families by setting the instance ID value from the IPv6 reserved range to the IPv4 reserved range (64 to 95) in the link LSAs. Enabling IPv4 support for OSPFv3 is straightforward and only involves two steps:
- Ensure that the IPv4 interface has an IPv6 address (global or link local) configured. Remember that configuring a global address also places a global address; alternatively, a link-local address can statically be configured.
- Enable the OSPFv3 process for IPv4 on the interface with the command ospfv3 process-id ipv4 area area-id.
Example 10-14 demonstrates the deployment of IPv4 using the existing OSPFv3 deployment.
What are two commands that will show the Address Family info for interfaces in OSPFv3?
The command show ospfv3 interface [brief] displays the address families enabled on an interface. When IPv4 and IPv6 are both configured on an interface, an entry appears for each address family. Example 10-16 lists the interfaces and associated address families.
The command show ospfv3 neighbor will also show this info. Example 10-17 shows how to view the OSPFv3 neighbors to display the neighbors enabled for IPv4 and IPv6 as separate entities.
