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The unknown multicast traffic suppress function on OLT causes Multicast stream freezes

Publication Date:  2012-07-25 Views:  57 Downloads:  0
Issue Description
A customer  discovered that some subscriber connected to MDU(MA5652G) have multicast stream freeze problem, to find out the cause they configured traffic mirror for vlan8(multicast vlan) on the uplink port on OLT, then the problem disappeared.
When the traffic mirror is deleted, the problem happens again.
traffic-mirror:
port 0/19/0: 
 Inbound:
   Matches: Acl 4000 rule 5     running
   Mirror to: port 0/20/1
OLT version: MA5600V800R005C32B150HP0001
Alarm Information
No alarm
Handling Process
1. Confirmed that this problem happens to all customers, no matter connected to MDU or ONT.
2. Confirmed that this problem happens to all programs configured.
3. According to above analysis, tried to disable multicast traffic suppress, problem solved.
Root Cause
There is a unknown multicast traffic suppress configured by default by the OLT which can be displayed with command:
MA5600T(config-if-giu-0/19)#display traffic-suppress all
Since this customer use double tagged vlan for multicast traffic, the OLT will broadcast these packets to GPBC boards as unknown multicast packets and thus affected by the suppress parameter.
The unknown multicast traffic suppress function is realized by acl 4000 rule ffff, and mirror function is also configured with acl 4000 rule 5, whose rule is permit with action mirror. 
since the last configured rule will take effect first, so this mirror function permits all the traffic flow and the packets will not be discarded. 
  
Suggestions
Disable multicast traffic suppress manually:
e.g.
MA5600T(config-if-giu-0/19)#undo traffic-suppress 0 multicast

END