关系数据库有多种操作，其中从一个关系中选取某些属性的操作为 _______。A．投影B．选择C．连接D．交A．

A. If a packet is sent to a multicast group address, the multicast frame contains the source multicast address.

B. A router does not have to be a member of a multicast group to recei ve multicast data.

C. A router must be a member of a multicast group to send to the group.

D. A router does not have to be a member of a multicast group to send to the group.

E. If a packet is sent to a multicast group address, all members of the multic ast group will receive it.

F. A router must be a member of a multicast group to receive multicast data.

A．228.10.10.7

B． 229.11.10.7

C． 229.138.10.7

D． 229.138.10.8

E． 228.10.10.8

F． 228.10.138.7

A．Unicast

B． Private

C． Broadca st

D． Public

E． Multicast

F． Anycast

A．169.254.23.59

B． 223.254.255.254

C． 225.1.1.1

D． 227.43.34.2

E． 238.3.3.3

F． 249.1.2.3

A. There are three IGMP modes: dense mode, sparse mode, and sparse - dense mode

B. IGMP is used to register individual hosts with a multicast group

C. IGMP version 3 enables a multicast receiving host to specify to the router which sources it should forward traffic from

D. IGMP messages a re IP datagrams with a protocol value of 2, destination address of 224.0.0.2, and a TTL value of 1

E. IGMP is a multicast routing protocol that makes packet - forwarding decisions independent of other routing protocols such as EIGRP

F. IGMP snooping ru ns on Layer 3 routers

A. EIGRP supports five generic packet types, including hello, database description (DBD), link state request (LSR), link - state update (LSU), and LSAck.

B. EIGRP sends periodic hello packets to the multicast IP address 224.0.0.10.

C. EIGRP will not form a neighbor relationship with another peer when their K values are mismatched.

D. EIGRP sends periodic hello packets to the multicast IP address 224.0.0.9.

E. E IGRP will form a neighbor relationship with another peer even when their K values are mismatched.

F. EIGRP supports five generic packet types, including hello, update, query, reply, and ACK packets.

A. only the low-order 23 bits of the MAC address are used to map IP addresses

B. only the low-order 24 bits of the MAC address are used to map IP addresses

C. only the high-order 23 bits of the MAC address are used to map IP addresses

D. only the low-order 23 bits of the IP address are used to map MAC addresses

E. the 0x01004f MAC address prefix is used for mapping IP addresses to MAC addresses

F. the 0x01005e MAC address prefix is used for mapping IP addresses to MAC addresses

A. a request made by a node to join a specified multicast group

B. a request made by a node for its IP address

C. a request made by a node for the IP address of the DHCP server

D. a request made by a node for the IP address of the local router

A. show ip dhcp external

B. show dhcp binding relay-proxy

C. show ip dhcp binding relay-proxy

D. show dhcp relay proxy binding