[AusNOG] IP Multicast Persistent Duplicate Packet Issue

Roman Islam romislam at gmail.com
Wed Apr 6 17:30:03 AEST 2022


Hi Everyone,

Has anyone experienced a TETRA Radio application issue if underlying IP
multicast transport sends persistent duplicate packets?

Here is my scenario as below:

PIM is running on the MPLS L3 VPN environment. C multicast is running on a
single VRF (TETRA) only. Source is running behind a dual home PE. HSRP, PIM
DR path is via PE1 to the source. Anycast RP is configured with PE1 & PE2.

On the receiver side there is a single PE. When I check (S,G) route on the
receiver side PE default MDT is working as expected. After the threshold
exceeds it switches to the data MDT. PIM Assert mechanism winner is PE2
though (Since PE 2 has the highest IP and source is behind dual home PE
with equal cost I guess).

Can this be a reason for persistent duplicate multicast packets at the
receiver side; since the assert winner is PE2 but HSRP, PIM DR path is via
PE1 to the source?

If this is the case is there any way to manually configure the assert
winner to PE1?

Roman
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