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Questions and Answers
What happens when a timer expires for a host group?
What happens when a timer expires for a host group?
What does Report Suppression achieve?
What does Report Suppression achieve?
What is the significance of a TTL value of 1 for IGMP messages?
What is the significance of a TTL value of 1 for IGMP messages?
What occurs when TTL is greater than 1 in multicast routing?
What occurs when TTL is greater than 1 in multicast routing?
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What is the maximum response time (D) related to?
What is the maximum response time (D) related to?
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What is the range of multicast addresses classified as Class D?
What is the range of multicast addresses classified as Class D?
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What multicast address is used to reach all hosts and all routers on a network?
What multicast address is used to reach all hosts and all routers on a network?
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Which multicast address range is reserved for routing protocols?
Which multicast address range is reserved for routing protocols?
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What will happen to a multicast address when an application using it is terminated?
What will happen to a multicast address when an application using it is terminated?
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Which of the following addresses is reserved for IGMPv3?
Which of the following addresses is reserved for IGMPv3?
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What is the hexadecimal format of a MAC address?
What is the hexadecimal format of a MAC address?
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Which multicast address is specifically designated for all DVMRP routers on a network?
Which multicast address is specifically designated for all DVMRP routers on a network?
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Which of the following statements is true regarding multicast datagrams directed to reserved address ranges?
Which of the following statements is true regarding multicast datagrams directed to reserved address ranges?
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What does a unicast Ethernet frame contain?
What does a unicast Ethernet frame contain?
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What is the hexadecimal representation of a broadcast Ethernet frame's address?
What is the hexadecimal representation of a broadcast Ethernet frame's address?
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Which range of addresses are reserved for IP multicast?
Which range of addresses are reserved for IP multicast?
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What does the -r option do when using netstat?
What does the -r option do when using netstat?
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Which option will netstat use to show both multicast and unicast addresses?
Which option will netstat use to show both multicast and unicast addresses?
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What component of the MAC address is assigned by the manufacturer?
What component of the MAC address is assigned by the manufacturer?
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What address does a multicast frame contain?
What address does a multicast frame contain?
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Which statement about the address range 224.0.0.0 to 239.255.255.255 is true?
Which statement about the address range 224.0.0.0 to 239.255.255.255 is true?
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What is the main function of the Internet Group Management Protocol (IGMP)?
What is the main function of the Internet Group Management Protocol (IGMP)?
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Which version of IGMP introduced a leave processing mechanism?
Which version of IGMP introduced a leave processing mechanism?
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What does a multicast router do when there are no hosts joined to a multicast group?
What does a multicast router do when there are no hosts joined to a multicast group?
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In IGMP, what is the purpose of a General Query?
In IGMP, what is the purpose of a General Query?
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What additional capability does IGMPv3 provide compared to earlier versions?
What additional capability does IGMPv3 provide compared to earlier versions?
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What happens in IGMPv1 when a host wants to leave a multicast group?
What happens in IGMPv1 when a host wants to leave a multicast group?
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How does a host respond when it receives an IGMP query for a multicast group it belongs to?
How does a host respond when it receives an IGMP query for a multicast group it belongs to?
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Which of the following statements regarding IGMP is true?
Which of the following statements regarding IGMP is true?
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What is the main purpose of an IGMP leave message?
What is the main purpose of an IGMP leave message?
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Which address is used as the destination IP address when sending an IGMP group-specific query?
Which address is used as the destination IP address when sending an IGMP group-specific query?
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What is the maximum length of IGMP messages?
What is the maximum length of IGMP messages?
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Which of the following IGMP types correspond to a report message in IGMPv1?
Which of the following IGMP types correspond to a report message in IGMPv1?
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In IGMPv1, which of the following statements is true regarding leaving a group?
In IGMPv1, which of the following statements is true regarding leaving a group?
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What happens when a host receives a query in IGMP?
What happens when a host receives a query in IGMP?
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Which version of IGMP first introduced the group leave functionality?
Which version of IGMP first introduced the group leave functionality?
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If a host needs to leave a specific multicast group in IGMPv3, which address is used for the leave message?
If a host needs to leave a specific multicast group in IGMPv3, which address is used for the leave message?
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What does the second octet of an IGMP message represent?
What does the second octet of an IGMP message represent?
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Which destination IP address is used for an IGMP general query?
Which destination IP address is used for an IGMP general query?
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Study Notes
Wireless Mobile & Multimedia Networking Lecture 2: IGMP
- IGMP is a protocol for IP multicast
- IGMP operates on a single Ethernet segment
- Multicast routers track membership in multicast groups
- Routers maintain a table of multicast groups that hosts have joined
- Routers forward packets only when a host is still in the group
- IGMP supports joining, leaving, membership queries, and membership reports
Multicast Addresses
- Class D addresses are multicast addresses
- The range of multicast addresses is from 224.0.0.0 to 239.255.255.255
- Multicast addresses are dynamically assigned
- Multicast addresses are released (implicitly) when an application terminates
- Specific ranges of multicast addresses are reserved for routing protocols and topology discovery
Reserved IP Multicast Addresses
- The range 224.0.0.0 to 224.0.0.255 is reserved
- Multicast routers do not forward multicast datagrams with destination addresses in this range
- Important permanent multicast groups include:
- 224.0.0.1: All hosts and routers on a network
- 224.0.0.2: All routers on a network
- 224.0.0.22: IGMPv3
- Other protocols may reserve specific multicast groups
IP Multicast Addresses for Autonomous Systems (AS)
- Each AS (autonomous system) owns a range of multicast addresses
- Example: AS 0x8080 owns the range 233.128.128.0 to 233.128.128.255
MAC Addresses
- MAC addresses consist of 12 hexadecimal digits (48 bits)
- Ethernet addresses have three types:
- Unicast: Unique destination MAC address
- Broadcast: All binary 1s (FF:FF:FF:FF:FF:FF)
- Multicast: Unique multicast MAC address for applications, protocols, or data streams
Mapping Multicast Address: IP -> MAC
- Class D IP addresses (with 01:00:5e in the first 3 bytes) are reserved for IP multicast
netstat command
-
netstat -nra
displays numeric IP addresses, routing table, and all addresses
IGMP Messages
- IGMP query: used by routers to learn about groups on an attached network (general or group-specific)
- IGMP membership report: a host responds to an IGMP query indicating membership in certain groups
- IGMP join report: a process joining a multicast group
- IGMP leave: a process leaving a group (with some versions)
IGMP Protocol
- IGMP operates at the network layer
- It is specifically used for tracking multicast memberships
- The Destination IP address is a group address
- The Source IP address is the initiating host's address
IGMPv1 Packet Format
- IGMPv1 messages are 8 bytes long
- Includes version, type, checksum, and 32-bit class D address
IGMPv2 and IGMPv3 Packet Format
- These versions have a specific format which differ from IGMPv1
- The first octet defines the type; Query (0x11), vl Report (0x12), v2 Report (0x16), v3 Report (0x22), Leave (0x17)
Timing Issues
- Query interval: Hosts respond to queries with a delay (random value) to spread out reports
- Maximum response time: Maximum time a host waits before responding to a query
- Report suppression: Prevents duplicate reports
Time-To-Live (TTL)
- TTL is a scope-limiting parameter for IP multicast datagrams
- It controls the number of hops a multicast packet can travel
- IGMP messages always have TTL=1 to restrict them to the local network
- Multicast routers can have TTL > 1 to forward packets further
IGMP Versions Comparison
- A table comparing features of IGMPv1, IGMPv2, and IGMPv3 (e.g., message formats, join/leave functionality, query types) is also presented.
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Description
Explore the intricacies of IGMP, a protocol vital for IP multicast within Ethernet networks. This quiz covers multicast address ranges, membership management, and reserved IP multicast addresses critical for networking professionals. Test your understanding of these concepts essential for effective network design and operation.