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CCIE R&S - Multicast
CCIE R&S - Written - Multicast
| Question | Answer |
|---|---|
| What class and IPv4 range is reserved for multicast? | Class D, 224.0.0.0 - 239.255.255.255 |
| What is the multicast Local Link Range reserved for? | Reserved for routing protocols and other maintenance functions |
| What is the IPv4 multicast Local Link Range? | 224.0.0.0 - 224.0.0.255 (Local Network Control Block) |
| What is the ipv4 multicast Internet Application Range? | Range is 224.0.1.0 - 224.0.1.255 (Internetwork Control Block) |
| What is GLOP used for? | It is used for sourcing multicast content on the internet |
| How is GLOP assigned? | 233.AS_Value.Local_Assignment |
| What is the range of IPv4 multicast addresses that are administratively scoped for organizations? | 239.0.0.0 - 239.255.255.255 |
| What are the top 256 addresses in each Admin Scope reserved for? | Scope Relative Address, such as 239.255.255.249 (reserved for DHCPv4) |
| What is the disadvantage of IGMP Version 1 | Hosts have no way of notifying routers when they don't want the multicast stream |
| What major improvement was made with IGMP Version 2? | Hosts now have the ability to send a 'Leave Group' message |
| What is the benefit to IGMP Version 3 | It adds Source Specific Multicast (SSM) |
| What three messages are used by IGMP hosts? | Membership Report, Version 1 Membership Report, Leave Group |
| What two types of IGMP messages are used by routers? | General Query and Group-Specific Query |
| Command to turn multicast routing on globally | ip multicast-routing |
| Command to enable PIM on an interface | ip pim [sparse-mode | dense-mode| sparse-dense-mode] |
| Command to verify IGMP operation on an interface | show ip igmp interface |
| What is the PIM traffic forwarding concept? | Multicast traffic radiates away from a source rather than to a destination |
| What are the two types of PIM trees? | Source-Based Tree and Shared Tree |
| What does (S, G) mean? | Source-Based Tree where 'S' denotes class A,B, or C source IP address and 'G' denotes the multicast group address |
| What does (*, G) mean? | Shared Tree where '*' denotes any source and 'G' denotes multicast group address |
| What are the three modes of PIM? | Dense Mode, Sparse Mode, and Sparse-Dense Mode |
| How often does PIM DM flood and prune? | Every 3 minutes |
| Which PIM mode has an explicit join approach? | PIM Sparse Mode |
| What is a negative effect of PIM DM? | Requires a lot of CPU overhead |
| What is a negative effect of PIM SM? | May have increased delay |
| What is necessary when multiple multicast routers are connect to a multi-access network? | A designated router |
| How is the multicast Designated Router elected? | Highest IP address, Loopback, then other interfaces |
| What is the function of the multicast Designated Router? | To send Join and Prune message to the RP |
| Name the technology that is a variation on the PIM-SM mode introduced to address issues for groups with a large number of sources | Bidirectional PIM |
| How does Bidirectional PIM forward traffic? | with (*,G) mechanisms only |
| What are the two functions of the multicast designated Forwarder for Bidirectional PIM? | To prevent loops and forward appropriate multicast traffic upstream |
| How is the multicast Bidirectional PIM Designated Forwarder elected? | Best Unicast route to the RP |
| What does reverse path forwarding mean? | Moving traffic away from the source, instead of to a destination |
| How does the RPF Check work? | It uses the unicast IP routing table to determine the upstream bath to the source and checks the interface that a multicast packet was received on |
| What is the primary loop prevention mechanism in multicast? | RPF Check |
| What are the three ways to fix an RPF failure? Which one is the best? | Run PIM DM over necessary links, Change the unicast routing table, or Create a Static Multicast Route |
| Command for creating static multicast route | ip mroute (source ip) (network mask) (interface) |
| What two methods exist for automatically assigning the Rendezvous Point? | Auto-RP and Bootstrap Router (BSR or PIM Version 2) |
| What is the term for routers that want to be RPs? | Candidate RPs |
| What is the flaw with Auto-RP? | It uses a dense multicast address to speak to clients to give them the RP (multicast) address (A problem in sparse mode only) |
| What multicast address is used by Candidate RPs in Auto-RP? | 224.0.1.39 |
| What multicast address is used by the mapping agent? | 224.0.1.40 |
| Command to declare candidacy for RP? | ip pim send-rp-announce |
| Command to announce Mapping Agent? | ip pim send-rp-discovery |
| What are the two fixes for the SM problem with Auto-RP? | Statically assign the RP or use the 'ip pim auto rp listener' on each SM router |
| What technology allows multiple RPs to load share and provide hot backups for each other? | Anycast RP |
| What protocol does Anycast RP rely on? | Multicast Source Discovery Protocol (MSDP) |
| What is the range of the IPv4 permanent multicast group? | 224.0.0.0 - 224.0.1.255 |
| What range of the IPv4 permanent multicast group is not routed? | 224.0.0.0 - 224.0.0.255 |
| What range of the IPv4 permanent multicast group is routed? | 224.0.1.0 - 224.0.1.255 |
| What is the IPv4 Source-Specific Multicast Range? | 232.0.0.0 - 232.255.255.255 |
| What is a IPv4 multicast transient address? What is its range? | A transient address must be shared by all users of the internet. They are all remaining multicast addresses that aren't reserved. |
| What are the three rules for mapping an IPv4 multicast address to a MAC address? | Start with hex 01005e. Followed by binary zero. Followed by last 23 bits of IP address |
| What are the three multicast distribution management protocols? | CGMP, IGMP, RGMP |
| What IP protocol number does IGMP datagram messages use? | 2 |
| What is the IP TTL set to in IGMP messages? | 1 |
| What is the default version of IGMP? | Version 2 |
| IGMP version 2 is automatically enabled when _____ and _____ are configured. | multicast routing, PIM |
| What are the four fields of an IGMP Version 2 message? | Type, Maximum Response Time, Checksum, Group Address |
| What are the four different messages that can be in the IGMP 'type' field? | Membership Query, Version 1 Membership Report, Version 2 Membership Report Leave Group |
| The IGMP maximum response time is only included in ______ messages. | query |
| How is the IGMP version 2 maximum response time measured? | |
| What is the default IGMP version maximum response time value? What is the range? | 100, 1-255 |
| What multicast address does IGMP version 3 use as a destination? | 224.0.0.22 |
| When does a IGMP host send an unsolicited Host Membership Report? | When the host first comes online or wants to join the group |
| In IGMP version 2, What does the router do when it receives a leave group message from a host? | Sends a group-specific query |
| What two values does an IGMP version 2 router use to determine if there are still listeners? What are their default values? | Last Member Query Count - 2, Last Member Query Interval - 1 second |
| How often are general queries sent by default in IGMP version 2? | Every 60 seconds |
| How does report suppression work in IGMP version 2 when hosts receive a general or group-specific query? | They start a random timer anywhere between 0 and the configured maximum response time. They will send their membership report at the end of that timer only if they have not heard another host's report |
| How does the IGMP version 2 Querier election work? | Routers send their general query messages to 224.0.0.1. Lowest address wins. |
| How do IGMP routers determine when an elected querier is dead? | 2 missed query intervals plus 1/2 query response interval = dead time. If no queries within dead time, new election will take place. Default query interval is 125 seconds. Default query response interval is 10 seconds. |
| What layer does CGMP operate at? | Layer 2 |
| In CGMP, only _____ produce messages. | routers |
| In CGMP, only _____ listen to messages. | switches |
| What is the destination MAC address used for CGMP messages | 0100.0cdd.dddd |
| What addresses are included in CGMP messages? | Group Destination Address (GDA) and Unicast Source Address (USA) |
| How often does a router send a CGMP message? | Every 60 seconds |
| When a router sends a leave message in CGMP for a group, what is the GDA and USA set to? | Group address, zero |
| When a router wants the switch to release the CGMP router port, what is the GDA and USA set to in that leave message? | Zero, Router MAC |
| What are GDA and USA values when the command 'clear ip cgmp' is given on a router? | Zero, Zero |
| In CGMP, what does a router do when it receives an IGMP message from a host? | It creates a CGMP message with USA and GDA set and sends it to the CGMP well-known MAC address |
| How does a switch with IGMP Snooping determine which ports have routers connected to them? | Switch listens to routing protocol messages from well-known router MAC addresses. When it hears them, those ports are added to GDA list for that VLAN. |
| What three things does a IGMP Snooping switch do when it receives an IGMP report? | CPU looks at the GDA, creates CAM table entry, and adds it to the port to the entry |
| What is the default IGMP snooping Last Member query interval? | 1000 seconds |
| Which method is less efficient, IGMP Snooping or CGMP? | IGMP Snooping |
| What address is used for all RGMP messages sent to? | 224.0.0.25 |
| Since RGMP does not work with CGMP, when one is _____ the other is _____. | |
| How often are RGMP Hello messages sent? | Every 30 seconds |
| What does a switch do when it receives an RGMP hello message? | Stop forwarding all multicast traffic on that port |
| How does a router indicate that it wants to receive multicast traffic for a group? | Join G message, G is the multicast group |
| How does a router indicate that it wants to stop receiving multicast traffic for a group? | Leave G message, G is the multicast group |
| When a switch receives an RGMP Bye message, what action does it take? | Forwards all multicast traffic on that port |
| What is the default version of PIM? | Version 2 |
| What type of messages does PIM Version 1 use for adjacencies? | Query Messages |
| What IP protocol number does PIM Version 1 use? What multicast destination? | 2, 224.0.0.2 |
| What is the hello time and dead time of PIM version 2? | 30 seconds, Dead timer is 3 times hello |
| What IP protocol and destination address does PIM Version 2 use? | IP protocol 103, 224.0.0.13 |
| Where does PIM Version 3 have to be configured? | Only on edge routers |
| Aside from not having any devices interested, why would a PIM Dense mode router prune? | Receiving packets on non-RPF interface |
| What does a PIM Register message contain? | Multicast packets encapsulated in Unicast register header |
| When the RP replies, what does it send to the source router in response to a Register message? | Register Stop message |
| What does the source router do once it receives a Register Stop message from RP? | Set a 1 minute timer before it sends again |
| 5 seconds before Register Stop timer expires on source router, what does it send to the RP? | Register message with Null-Register bit set (no encapsulated packets) |
| What PIM version 2 message is used to form adjacencies? | Hello |
| What PIM version 2 message is used before timer expiration to keep the pruned state? | State Refresh |
| What PIM version 2 message is used to request traffic that was previously pruned? | Graft |
| What PIM version 2 message is sent in response to a Graft message? | Graft Acknowledgment |
| What PIM version 2 message is used for adding and removing branches to the PIM tree? | Join/Prune Message |
| Once prune messages are sent in PIM version 2, how long does the receiving router wait for Prune Override messages? | 3 seconds |
| What PIM version 2 message is used to determine who will be the multicast forwarder on a multi-access segment? | Assert |
| What three things are checked to determine which router will become the designated forwarded on a multi-access segment in PIM version 2? | Lowest administrative distance to the source, lowest routing protocol metric to the source, highest IP address] |
| Once (*, G) entries have been made, when does shortest path switchover take place by default | As soon as the router receives its first multicast packet |
| How is the PIM version 2 value for spt-threshold measured? | kbps |
| What does an 'R' mean in the multicast routing table? | (S,G) entry is pointing toward the RP |
| What does an 'F' mean in the multicast routing table? | Software is registering for a multicast source |
| What does an 'T' mean in the multicast routing table? | Packets received on shortest-path source tree |
| When is a PIM Designated Router elected? | Only in when IGMPv1 is used |
| What does a source router do in Bidirectional PIM instead of using register messages? | Send traffic toward the RP |
| What are the two options of multicast scoping? | TTL and Administrative Scoping |
| What is the default TTL value on all Cisco interfaces? | 0 |
| What are the other two multicast protocols besides PIM? | DVMRP and MOSPF |
| What is the multicast source address in PIM dense mode? | Actual source address of multicast packets |
| What is the multicast source address in PIM sparse mode? | RP |
| How often are Auto-RP Candidate messages sent? | Every minute |
| How does the Auto-RP mapping agent determine which router will be the RP for a multicast group? | Highest IP address |
| What happens to the traffic that began before the router learned of a RP? | Traffic still uses dense-mode rules |
| How is a BSR router different from an Auto-RP Mapping agent? | BSR router sends all group-to-RP mapping information so PIM routers can select their own RP |
| What destination does BSR use to flood messages out all non-RPF interfaces? | 224.0.0.13 |
| If there are multiple BSR routers, which one becomes active? | Highest IP address |
| How does Anycast's MSDP work? | Peers are statically configured and then share all known multicast source information with each other |
| How often are MSDP messages sent? | Every 60 seconds |
Created by:
ajballer15
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