Hitachi GR2000 Series Installation Manual page 288

In the system configuration allowing mixed use with a device other than this
device, multi-cast communication may become impossible due to difference in
the calculation range of check sum for PIM-Register message (capsulated packet).
If the Register message does not perform multi-cast relaying at the rendezvous
point due to a check sum error, change the range to calculate the PIM check sum
by using the configuration defining information of this device. For details, please
refer to the "Configuration definition command reference, pim".
4.14.2 Redundant route (route switching due to impediment)
Please pay attention to the following points if the multicast route is a redundant
route ins this router.
4.14.2.1 When using PIM-DM
In the case of PIM-DM, the time required to switch the multicast packet
communication from a redundant route is a maximum of 210 seconds.
4.14.2.2 When using DVMRP