IP Multicast Persistent Duplicate Packet Issue

Wed Apr 6 23:45:21 UTC 2022

	You can likely set "ip pim dr-priority" to get what you want

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti/command/imc-cr-book/imc_i3.html#wp1384657000

	- Jared

On Thu, Apr 07, 2022 at 09:07:34AM +1000, Roman Islam wrote:
> Thanks Jared. Yes it is SSM. I will try to flip PIM priority and align HSRP
> active.
> 
> My initial thought was keeping everything as it is. Can I simply flip PIM
> assert winner to PE1. Same way we can manually select STP root. Looks like
> this is probably not an option. Didn't find relevant doc on how to
> manipulate PIM assert winner in Cisco boxes though. Highest IP is the
> winner if IGP costs are the same to the source.
> 
> R
> 
> 
> On Thu, Apr 7, 2022 at 3:02 AM Jared Mauch <jared at puck.nether.net> wrote:
> 
> > If this is ASM, what device is the RP?  You may want to configure MSDP
> > between PE1/PE2 to help if that’s the case, or is this SSM or something
> > else you may want to just flip the PIM priority to make it pick what you
> > want and see if you can tie it to your HSRP (Cisco, might I suggest VRRP so
> > you could do dual-vendor later?) state, perhaps with EEM script to keep the
> > config in sync if required.
> >
> > - Jared
> >
> > > On Apr 6, 2022, at 3:25 AM, Roman Islam <romislam at gmail.com> wrote:
> > >
> > > 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
> >
> >

-- 
Jared Mauch  | pgp key available via finger from jared at puck.nether.net
clue++;      | http://puck.nether.net/~jared/  My statements are only mine.