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Multicast (S,G) entry 224.0.1.39 for non Mappig Agent router

Federico Olivieri
Level 1
Level 1

‎02-13-2018 03:37 AM - edited ‎03-08-2019 01:49 PM

I have a simple topology like this:

AutoRP.png

So, I have Auto-RP configured where R3 and R4 are RP and c-RP for the same group and R5 is mapping agent and R2 is just a PIM neighbor. R1 and R6 are multicast source and dest.

So, after the magic of the Auto-RP happens, I can see the mroute table correctly populated in R5 with the (S,G) for 224.0.1.39 (R3 and R4 RPs)  and 224.0.1.40 for R5 (itself) for receiving RP mapping (see output below)

R5#sh ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP-mapping agent (Loopback0)

Group(s) 224.1.1.1/32
  RP 3.3.3.3 (?), v2v1
    Info source: 3.3.3.3 (?), elected via Auto-RP
         Uptime: 00:09:35, expires: 00:02:08

R5#sh ip mroute
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
       L - Local, P - Pruned, R - RP-bit set, F - Register flag,
       T - SPT-bit set, J - Join SPT, M - MSDP created entry, E - Extranet,
       X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
       U - URD, I - Received Source Specific Host Report,
       Z - Multicast Tunnel, z - MDT-data group sender,
       Y - Joined MDT-data group, y - Sending to MDT-data group,
       G - Received BGP C-Mroute, g - Sent BGP C-Mroute,
       Q - Received BGP S-A Route, q - Sent BGP S-A Route,
       V - RD & Vector, v - Vector
Outgoing interface flags: H - Hardware switched, A - Assert winner
 Timers: Uptime/Expires
 Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 224.0.1.39), 00:06:12/stopped, RP 0.0.0.0, flags: DCL
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    FastEthernet1/0, Forward/Sparse-Dense, 00:06:12/stopped
    FastEthernet0/1, Forward/Sparse-Dense, 00:06:12/stopped
    FastEthernet0/0, Forward/Sparse-Dense, 00:06:12/stopped
    Loopback0, Forward/Sparse-Dense, 00:06:12/stopped

(4.4.4.4, 224.0.1.39), 00:06:06/00:02:14, flags: LT
  Incoming interface: FastEthernet1/0, RPF nbr 10.1.1.4
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:06:06/stopped
    FastEthernet0/0, Forward/Sparse-Dense, 00:06:06/stopped
    FastEthernet0/1, Forward/Sparse-Dense, 00:06:06/stopped

(3.3.3.3, 224.0.1.39), 00:06:12/00:02:07, flags: LT
  Incoming interface: FastEthernet0/0, RPF nbr 35.1.1.3
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:06:12/stopped
    FastEthernet0/1, Forward/Sparse-Dense, 00:06:12/stopped
    FastEthernet1/0, Forward/Sparse-Dense, 00:06:12/stopped

(*, 224.0.1.40), 00:06:12/stopped, RP 0.0.0.0, flags: DCL
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    FastEthernet1/0, Forward/Sparse-Dense, 00:06:12/stopped
    FastEthernet0/0, Forward/Sparse-Dense, 00:06:12/stopped
    Loopback0, Forward/Sparse-Dense, 00:06:12/stopped

(5.5.5.5, 224.0.1.40), 00:05:40/00:02:16, flags: LT
  Incoming interface: Loopback0, RPF nbr 0.0.0.0
  Outgoing interface list:
    FastEthernet0/0, Forward/Sparse-Dense, 00:05:40/stopped
    FastEthernet1/0, Forward/Sparse-Dense, 00:05:40/stopped

On R2, being a normal PIM Neighbor, I expected to see just and (S,G) for 224.0.1.40, however I see also entries for 224.0.1.39 as in R5. My understanding is that just mapping-agent join group for RP-announcement when the other PIN-Neighbors join just the RP-Discovery. Can you help me to understand this part?


R2#sh ip mroute
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
       L - Local, P - Pruned, R - RP-bit set, F - Register flag,
       T - SPT-bit set, J - Join SPT, M - MSDP created entry, E - Extranet,
       X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
       U - URD, I - Received Source Specific Host Report,
       Z - Multicast Tunnel, z - MDT-data group sender,
       Y - Joined MDT-data group, y - Sending to MDT-data group,
       G - Received BGP C-Mroute, g - Sent BGP C-Mroute,
       Q - Received BGP S-A Route, q - Sent BGP S-A Route,
       V - RD & Vector, v - Vector
Outgoing interface flags: H - Hardware switched, A - Assert winner
 Timers: Uptime/Expires
 Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 224.1.1.1), 00:12:56/00:03:09, RP 3.3.3.3, flags: S
  Incoming interface: FastEthernet0/0, RPF nbr 23.1.1.3
  Outgoing interface list:
    FastEthernet0/1, Forward/Sparse-Dense, 00:12:56/00:03:09

(*, 224.0.1.39), 00:13:57/stopped, RP 0.0.0.0, flags: DC
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    FastEthernet0/0, Forward/Sparse-Dense, 00:13:28/stopped
    FastEthernet0/1, Forward/Sparse-Dense, 00:13:28/stopped
    FastEthernet1/0, Forward/Sparse-Dense, 00:13:57/stopped

(3.3.3.3, 224.0.1.39), 00:10:55/00:01:37, flags: T
  Incoming interface: FastEthernet0/0, RPF nbr 23.1.1.3
  Outgoing interface list:
    FastEthernet1/0, Forward/Sparse-Dense, 00:10:55/stopped
    FastEthernet0/1, Forward/Sparse-Dense, 00:10:55/stopped

(4.4.4.4, 224.0.1.39), 00:12:54/00:01:47, flags: T
  Incoming interface: FastEthernet1/0, RPF nbr 10.1.1.4
  Outgoing interface list:
    FastEthernet0/1, Forward/Sparse-Dense, 00:12:54/stopped
    FastEthernet0/0, Forward/Sparse-Dense, 00:12:54/stopped

(*, 224.0.1.40), 00:13:57/stopped, RP 0.0.0.0, flags: DCL
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:13:57/stopped
    FastEthernet0/0, Forward/Sparse-Dense, 00:13:28/stopped
    FastEthernet0/1, Forward/Sparse-Dense, 00:13:28/stopped
    FastEthernet1/0, Forward/Sparse-Dense, 00:13:30/stopped

(5.5.5.5, 224.0.1.40), 00:12:56/00:02:27, flags: LT
  Incoming interface: FastEthernet1/0, RPF nbr 10.1.1.5
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:12:56/stopped
    FastEthernet0/1, Forward/Sparse-Dense, 00:12:56/stopped
    FastEthernet0/0, Prune/Sparse-Dense, 00:02:30/00:00:29

ThankYou!!!
 
 
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Federico Olivieri
Level 1
Level 1

‎02-13-2018 08:54 AM

I might have found the answer by myself. I remembered that Auto-RP use DM to join 224.0.1.39 and 224.0.1.40. I have done a quick test and isolated the PIM router from the RP and c-RP (just a point to point between PIM Router and mapping agent). Doing that, the (S,G) for 224.0.1.39 expire and removed from mroute table. It remains only a (*,G) for that group

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