• The Dell Networking OS implementation of MTRACE is in accordance with IETF draft draft-fenner-traceroute-ipm.• Multicast is not supported on secondary IP addresses.• Egress L3 ACL is not applied to multicast data traffic if you enable multicast routing.Multicast PoliciesThe Dell Networking OS supports multicast features for IPv4.IPv4 Multicast PoliciesThe following sections describe IPv4 multicast policies.• Limiting the Number of Multicast Routes• Preventing a Host from Joining a Group• Preventing a PIM Router from Forming an Adjacency• Preventing a Source from Registering with the RP• Preventing a PIM Router from Processing a JoinLimiting the Number of Multicast RoutesWhen the total number of multicast routes on a system limit is reached, the Dell Networking OS does not process any IGMP ormulticast listener discovery protocol (MLD) joins to PIM — though it still processes leave messages — until the number of entriesdecreases below 95% of the limit.When the limit falls below 95% after hitting the maximum, the system begins relearning route entries through IGMP, MLD, andMSDP.• If the limit is increased after it is reached, subsequent join requests are accepted. In this case, increase the limit by at least 10%for IGMP and MLD to resume.• If the limit is decreased after it is reached, Dell Networking OS does not clear the existing sessions. Entries are cleared after atimeout (you may also clear entries using the clear ip mroute command).NOTE: Dell Networking OS waits at least 30 seconds between stopping and starting IGMP join processing. You mayexperience this delay when manipulating the limit after it is reached.When the multicast route limit is reached, Dell Networking OS displays the following:3w1d13h: %RPM0-P:RP2 %PIM-3-PIM_TIB_LIMIT: PIM TIB limit reached. No new routes willbe learnt until TIB level falls below low watermark.3w1d13h: %RPM0-P:RP2 %PIM-3-PIM_TIB_LIMIT: PIM TIB below low watermark. Route learningwill begin.To limit the number of multicast routes, use the following command.• Limit the total number of multicast routes on the system.CONFIGURATION modeip multicast-limitThe range if from 1 to 16000.The default is 4000.NOTE: The IN-L3-McastFib CAM partition is used to store multicast routes and is a separate hardware limit that existsper port-pipe. Any software-configured limit may supersede this hardware space limitation. The opposite is also true, theCAM partition might not be exhausted at the time the system-wide route limit is reached using the ip multicast-limit command.558 Multicast Features
