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Community Member

PIM Join Packet - Encoded-Joined Source Address


Having a mad day, please could someone exactly explain what the Encoded-Joined Source Address-1 is (have marked the packet line with asterix's) and have included the RFC statement which is not making sense?

I know that the PIM join is sent with a ttl of 1 and that the router will look at the GDA in the join packet, determine where the RP is, add the IIF for the *,G, and then rebuild and send another pim join packet towards the RP (to the next hop router)

Frame 4 (72 bytes on wire, 72 bytes captured)

Arrival Time: Sep 10, 2002 01:30:45.363349000

Time delta from previous packet: 0.000004000 seconds

Time relative to first packet: 1.774545000 seconds

Frame Number: 4

Packet Length: 72 bytes

Capture Length: 72 bytes

Ethernet II, Src: 00:b0:c2:d1:8f:fc, Dst: 01:00:5e:00:00:0d

Destination: 01:00:5e:00:00:0d (01:00:5e:00:00:0d)

Source: 00:b0:c2:d1:8f:fc (Cisco_d1:8f:fc)

Type: IP (0x0800)

Trailer: 1DA490E8

Internet Protocol, Src Addr: (, Dst Addr: PIM-ROUTERS.MCAST.NET (

Version: 4

Header length: 20 bytes

Differentiated Services Field: 0xc0 (DSCP 0x30: Class Selector 6; ECN: 0x00)

1100 00.. = Differentiated Services Codepoint: Class Selector 6 (0x30)

.... ..0. = ECN-Capable Transport (ECT): 0

.... ...0 = ECN-CE: 0

Total Length: 54

Identification: 0x8d26 (36134)

Flags: 0x00

.0.. = Don't fragment: Not set

..0. = More fragments: Not set

Fragment offset: 0

Time to live: 1

Protocol: PIM (0x67)

Header checksum: 0x2e80 (correct)

Source: (


Protocol Independent Multicast

Version: 2

Type: Join/Prune (3)

Checksum: 0xa805 (correct)

PIM parameters


Groups: 1

Holdtime: 210

Group 0:

Join: 1

***** IP address: (SWR)

Prune: 0

Join Source Address-1 .. n

This list contains the sources that the sending router will forward multicast datagrams for if received on the interface this message is sent on.

Many thx indeed,


Community Member

Re: PIM Join Packet - Encoded-Joined Source Address


I believe that this join is creating an S,G entry, probably since the receiver's local router has determined that the traffic has exceeded the shortest path tree threshold,

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