Avaya 8800 Planning And Engineering, Network Design page 204

Multicast network design
Figure 96: Redundant MBR configuration with two separate VLANs
The following paragraphs describe a failure scenario possible with this configuration.
Assume that switch A has a multicast sender, and switch C has a receiver. The RP is at D. Then,
suppose that the unicast route on C allows data to reach source A through B, and that DVMRP tells
upstream switch B to reach the source on A. If so, data flows from A to B to C and traffic that comes
from D is discarded.
If the link between C and B fails, the unicast route on switch C indicates that the path to reach the
source is through D. If DVMRP has not yet learned the new route to the source, then it cannot
create an mroute for the stream when traffic is received and the stream is discarded.
Even after learning the route, DVMRP does not create an mroute for the stream. Thus, data is
discarded. To resolve this issue, stop the affected streams until DVMRP ages out the entries.
Another alternative is to reinitialize DVMRP (disable and reenable) and then restart the multicast
streams.
June 2016 Planning and Engineering — Network Design
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