CCNP CCNP Multicast and IPv6 3 — Questions and Answers
Question 1: What is the purpose of 6to4 tunneling in IPv6 transition?
- Encapsulates IPv6 packets inside IPv4 packets to traverse IPv4-only networks using the 2002::/16 prefix (Correct answer)
- Provides a stateful NAT translation between IPv6 and IPv4 addresses
- Assigns IPv4-compatible IPv6 addresses to dual-stack hosts
- Tunnels IPv4 traffic inside IPv6 packets for reverse compatibility
Correct answer: Encapsulates IPv6 packets inside IPv4 packets to traverse IPv4-only networks using the 2002::/16 prefix
6to4 automatically embeds the IPv4 address into a 2002::/16 IPv6 prefix, allowing isolated IPv6 sites to communicate over an IPv4 backbone without manual tunnel configuration.
Question 2: What is ISATAP (Intra-Site Automatic Tunnel Addressing Protocol) used for?
- Provides IPv6 connectivity between dual-stack nodes within an IPv4 site by using IPv4 addresses as the interface identifier (Correct answer)
- Connects two separate IPv6 sites over an IPv4 WAN using manually configured tunnels
- Translates IPv6 multicast addresses to IPv4 multicast addresses
- Assigns global unicast IPv6 addresses to hosts in an IPv4-only network
Correct answer: Provides IPv6 connectivity between dual-stack nodes within an IPv4 site by using IPv4 addresses as the interface identifier
ISATAP enables IPv6 communication within a site by embedding the IPv4 address into the interface ID (::0:5EFE:<IPv4>) to create an IPv6-over-IPv4 tunnel automatically.
Question 3: What is MLDv2 (Multicast Listener Discovery version 2) used for in IPv6 networks?
- Allows IPv6 hosts to report multicast group membership including source-specific requests to their local router (Correct answer)
- Provides router-to-router multicast routing for IPv6 networks
- Replaces PIMv6 for multicast tree building in IPv6 environments
- Manages multicast address allocation across the IPv6 address space
Correct answer: Allows IPv6 hosts to report multicast group membership including source-specific requests to their local router
MLDv2 is the IPv6 equivalent of IGMPv3 and allows hosts to signal both group membership and specific source preferences to their local router for SSM support.
Question 4: What is the key difference between PIM Dense Mode (PIM-DM) and PIM Sparse Mode (PIM-SM)?
- PIM-DM floods and prunes multicast traffic assuming receivers everywhere, while PIM-SM only forwards toward explicit receivers (Correct answer)
- PIM-SM uses an RP to flood traffic everywhere, while PIM-DM uses explicit join messages
- PIM-DM requires a Rendezvous Point while PIM-SM does not
- PIM-SM is used inside an AS while PIM-DM is used between ASes
Correct answer: PIM-DM floods and prunes multicast traffic assuming receivers everywhere, while PIM-SM only forwards toward explicit receivers
PIM-DM floods multicast traffic to all routers and then prunes branches without receivers, while PIM-SM uses explicit join messages and an RP, making it more scalable for WAN environments.
Question 5: What is Bidirectional PIM (Bidir-PIM) and when is it preferred over PIM-SM?
- A PIM mode where traffic flows in both directions along a shared tree, preferred for many-to-many multicast applications (Correct answer)
- A mode that creates both a shared tree and an SPT simultaneously from the start
- A PIM variant that uses two RPs for redundancy in case the primary RP fails
- An extension of PIM-SM that removes the need for source registration with the RP
Correct answer: A PIM mode where traffic flows in both directions along a shared tree, preferred for many-to-many multicast applications
Bidir-PIM builds a bidirectional shared tree rooted at the RP, allowing traffic to flow both toward and away from the RP, making it more scalable for many-to-many communication patterns.
Question 6: In a dual-stack IPv6 deployment, what is the purpose of a DHCPv6 prefix delegation (DHCPv6-PD)?
- Allows an ISP or upstream router to delegate an IPv6 prefix to a customer router for sub-allocation to its downstream interfaces (Correct answer)
- Provides stateful IPv6 address assignment to individual hosts on a LAN
- Assigns a unique /128 loopback address to each router in the network
- Translates DHCPv4 lease requests into DHCPv6 format for dual-stack hosts
Correct answer: Allows an ISP or upstream router to delegate an IPv6 prefix to a customer router for sub-allocation to its downstream interfaces
DHCPv6-PD (RFC 3633) enables an upstream device to delegate an IPv6 prefix (typically /48 or /56) to a CPE router, which then sub-delegates /64 prefixes to its LAN interfaces.
CCNP CCNP Multicast and IPv6 3
What is the purpose of 6to4 tunneling in IPv6 transition?