All things related to multicast

[Bill Nickless <>]

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Michael (good to hear from you again!)

Where are your PIM Rendezvous Points in this picture?  What are their IP 
addresses?

I'm assuming that you have one PIM domain (that is, a collection of routers 
all sharing a PIM RP) at your "Internal Campus."

My first guess would be to check the actual PIM Rendezvous Point address of 
your "Internal Campus Router."  Remember that the MSDP RPF rules check the 
RP-address, not the address of the S in the (S,G).  If your "Internal 
Campus" router is a Cisco, you can discover the actual PIM Rendezvous Point 
address being put into the MSDP SA by running a command like the following:

Kiwi#show ip pim rp mapping in-use
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
This system is an RP-mapping agent
This system is the Bootstrap Router (v2)

Group(s) 224.0.0.0/4
   RP 192.5.170.2 (kiwi-loop.anchor.anl.gov), v2v1
     Info source: 192.5.170.2 (kiwi-loop.anchor.anl.gov), via Auto-RP
          Uptime: 3d05h, expires: 00:02:52

RPs in Auto-RP cache that are in use:
Group(s): 224.0.0.0/4,   RP: 192.5.170.2

It would not surprise me to discover that your RP has picked (or been 
configured with) an address that you don't have in your static mroutes in 
the "GigaPOP Border Router," and/or is not in the BGP NLRI=Multicast 
announcements.

Finally, ignore (thoroughly) anything you see from 'show ip mroute' on the 
GigaPOP Border Router until the MSDP SA shows up in

   show ip msdp sa-cache <group number>

because that's what you have to fix first.  'show ip mroute' is useless 
unless and until you get MSDP working.  And even when it is working, the 
*ONLY* router that will have the A flag in the 'show ip mroute' state will 
be the PIM RP/MSDP speaker that is responsible for the MSDP SA being 
generated.  Also, the MSDP SA will *NOT* show up in 'show ip msdp sa-cache' 
on the advertising router.

Hope this helps,






At 10:58 PM 1/7/2001 -0500, Michael H. Lambert wrote:
>All,
>
>I'm probably just demonstrating my cluelessness, but a session we are trying
>to announce isn't making it to Abilene and I can't figure out why.
>
>Topology (PIM SM [or Sparse/Dense] on all interfaces):
>
>    +-------+                 +-------+                  +--------+
>    |Abilene|  BGP UC+MC NLRI |GigaPoP|  Static mroutes  |Internal|
>    | Core  |<--------------->|Border |<---------------->| Campus |
>    |Router |      MSDP       |Router |       MSDP       | Router |
>    +-------+                 +-------+                  +--------+
>
>Note:  The "Internal Campus Router" is not our campus unicast border routers
>(which are a pair of UNIX boxes running GateD and screend).
>
>The multicast boundary and SA filter access lists are at least close to the
>BCP.
>
>A host inside our campus is announcing a session.  On our internal router, I
>see (from "show ip mroute 224.2.127.254"):
>
>(128.182.61.51, 224.2.127.254), 00:04:04/00:00:01, flags: CLTA
>   Incoming interface: GigabitEthernet5/0/0.1, RPF nbr 0.0.0.0
>   Outgoing interface list:
>     ATM0/0.2, Forward/Sparse-Dense, 00:04:04/00:03:25
>     GigabitEthernet5/0/0.7, Forward/Sparse-Dense, 00:04:04/00:02:54
>
>My understanding of the flags is that "A" means that this (S,G) (and any
>session announcements in it) is being announced via MSDP.
>
>Now, on our GigaPoP border router:
>
>(128.182.61.51, 224.2.127.254), 00:31:58/00:02:19, flags: CLMT
>   Incoming interface: ATM5/0/0.2, RPF nbr 192.88.115.130, Mroute
>   Outgoing interface list:
>     ATM5/0/0.4, Forward/Sparse-Dense, 00:31:10/00:02:35
>     ATM5/0/0.6, Forward/Sparse-Dense, 00:31:11/00:03:04
>     Loopback0, Forward/Sparse-Dense, 00:31:58/00:02:51
>     ATM5/0/0.3, Forward/Sparse-Dense, 00:31:58/00:02:55
>
>The "M" flag suggests that this router is hearing the (S,G) via MSDP, but I
>take it that the lack of an "A" flag means it is not being announced.  The
>RPF neighbor is correct.  In fact, if I do a "show ip rpf 128.182.61.51" on
>the Abilene core router (CLEV), I get the expected result.  (None of the
>outgoing interfaces is the Abilene interface.)
>
>My understanding is that nobody in the outside world can see our session
>announcement unless (128.182.61.51, 224.2.127.254) is announced to Abilene
>by our border router.
>
>I'm at a loss as to how to track this one down.  Can anyone offer any
>suggestions?
>
>Michael
>
>+-------------------------------------------------------------------------+
>| Michael H. Lambert, Network Engineer             Phone: +1 412 268-4960 |
>| Pittsburgh Supercomputing Center                 FAX:   +1 412 268-8200 |
>| 4400 Fifth Avenue, Pittsburgh, PA  15213         
>
>        |
>+-------------------------------------------------------------------------+

===
Bill Nickless    http://www.mcs.anl.gov/people/nickless      +1 630 252 7390
PGP:0E 0F 16 80 C5 B1 69 52 E1 44 1A A5 0E 1B 74 F7     


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