48502: 22: 20: 40: DVMRP: Graft source 192.168.1.105, group 224.1.1.102: 22: 20: 40: DVMRP: Send graft-ACK on vlan1 to 105.1.1.2, len 1602: 22: 20: 40: DVMRP: Graft-Ack Vers: majorv 3, minorv 25502: 22: 20: 40: DVMRP: Graft-ACK source 192.168.1.105, group 224.1.1.116.5.4.2 DVMRP Troubleshooting HelpIn configuring and using DVMRP protocol, the DVMRP protocol may fail to run properlydue to reasons such as physical connection failure or wrong configurations. The usershould ensure the following: Good condition of the physical connection. All interface and link protocols are in the UP state (use “show interfaces status”command). Ensure the interface has an IP address properly configured (use “ip address”command). Next, enable DVMRP on the interface (use the “ip dvmrp” command). Multicast protocols use unicast routes to perform RPF check, for this reason, theunicast route correctness must be ensured. (DVMRP uses its own unicast route table,use the “show ip dvmrp route” command to view that table.) If connectivity with CISCO is required, make sure the CISCO connex command isconfigured (use “ip dvmrp cisco-compatible” command)16.6 IGMP16.6.1 Introduction to IGMPIGMP (Internet Group Management Protocol) is a TCP/IP protocol responsible for IPmulticast member management. It is used to establish and maintain multicast groupmembership between IP hosts and direct neighbor multicast switches. IGMP does notinclude the populating and maintenance of membership between multicast switches,which is covered by multicast routing protocols. All hosts participate in multicast mustimplement IGMP.Hosts participate in IP multicast can join/quit multicast groups at any position, any time,and of any number. The multicast switches do not save all host memberships, which isalso impractical. They just obtain information about whether receivers of a multicast group(group member) exist in network segments connecting to its interfaces. As to the hosts,they only need to keep the information about the multicast groups joined.IGMP is asymmetric for hosts and switches: The hosts respond IGMP query packets sent
