Multicast routing issue

Unanswered Question
Feb 20th, 2012

Hi all,

i'm facing a strange problem with multicast routing. I have got a cisco3750 switch configured with different VLANs (just to keep things simple).

On VLAN 5 I have got a Linux box running Mediatomd dlna media server and on VLAN 6 I've got 2 different dlna clients : one Samsung TV and one Philips WAS7500 station. I configured both VLANs to be in dense-mode and the TV gets connected to the Media Server without problems, but the Philips stations doesn't. From the linux box i can ping the Philips stations (acutally the TV doesn't reply to ping which is a standard behaviour i guess). When trying to ping the multicast address both clients should be joining from the Linux box i don't get any reply. Please find hereafter some output i get from variuos show/debug commands from the switch :

CISCO3750G#sh ip igmp groups

IGMP Connected Group Membership

Group Address    Interface                Uptime    Expires   Last Reporter   Gr

oup Accounted

239.255.255.250  Vlan6                    00:42:56  00:02:50  192.168.2.137     (Philips station)

224.0.1.40       Vlan5                    1d06h     00:01:57  192.168.2.1

CISCO3750G#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,

       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

       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

(*, 239.255.255.250), 3d02h/stopped, RP 192.168.2.129, flags: SJC

  Incoming interface: Null, RPF nbr 0.0.0.0

  Outgoing interface list:

    Vlan6, Forward/Dense, 00:44:02/00:00:00

(192.168.2.137, 239.255.255.250), 01:22:45/00:02:58, flags: PT     (Philips station)

  Incoming interface: Vlan6, RPF nbr 0.0.0.0

  Outgoing interface list: Null

(192.168.2.2, 239.255.255.250), 1d07h/00:02:38, flags: T     (Linux box)

  Incoming interface: Vlan5, RPF nbr 0.0.0.0

  Outgoing interface list:

    Vlan6, Forward/Dense, 00:44:02/00:00:00

(*, 224.0.1.40), 4d11h/00:02:48, RP 192.168.2.129, flags: SJCL

  Incoming interface: Null, RPF nbr 0.0.0.0

  Outgoing interface list:

    Vlan5, Forward/Dense, 1d06h/00:00:00

CISCO3750G#sh ip mroute count

IP Multicast Statistics

4 routes using 2220 bytes of memory

2 groups, 1.00 average sources per group

Forwarding Counts: Pkt Count/Pkts(neg(-) = Drops) per second/Avg Pkt Size/Kilobi

ts per second

Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 239.255.255.250, Source count: 2, Packets forwarded: 3986, Packets receiv

ed: 1197

  RP-tree: Forwarding: 0/0/0/0, Other: 1192/0/1192

  Source: 192.168.2.137/32, Forwarding: 502/1/1/0, Other: 4/0/0

  Source: 192.168.2.2/32, Forwarding: 3484/0/1/0, Other: 1/0/0

Group: 224.0.1.40, Source count: 0, Packets forwarded: 0, Packets received: 0

CISCO3750G#sh ip mcache

IP Multicast Fast-Switching Cache

(192.168.2.137/32, 239.255.255.250), Vlan6, Last used: mdfs, MinMTU: 18010

(192.168.2.2/32, 239.255.255.250), Vlan5, Last used: mdfs, MinMTU: 1500

CISCO3750G#sh ip rpf 192.168.2.2

RPF information for ? (192.168.2.2)

  RPF interface: Vlan5

  RPF neighbor: ? (192.168.2.2) - directly connected

  RPF route/mask: 192.168.2.0/25

  RPF type: unicast (connected)

  RPF recursion count: 0

  Doing distance-preferred lookups across tables

CISCO3750G#sh ip rpf 192.168.2.137

RPF information for ? (192.168.2.137)

  RPF interface: Vlan6

  RPF neighbor: ? (192.168.2.137) - directly connected

  RPF route/mask: 192.168.2.128/26

  RPF type: unicast (connected)

  RPF recursion count: 0

  Doing distance-preferred lookups across tables

CISCO3750G#sh ip mroute active

Active IP Multicast Sources - sending >= 4 kbps

a negative Rate counts pps being fast-dropped

CISCO3750G#sh ip pim int

Address          Interface                     Ver/   Nbr    Query  DR     DR

                                                       Mode   Count  Intvl  Prior

192.168.2.1         Vlan5                    v2/D   0      30     1      192.168.2.1

192.168.2.129     Vlan6                    v2/D   0      30     1      192.168.2.129

20 2012 22:55:00.209: MRT(0): Update Vlan6/239.255.255.250 in the olist of (*,239.255.255.250), Forward state - MAC not built

Feb 20 2012 22:55:00.209: MRT(0): Update Vlan6/239.255.255.250 in the olist of (192.168.2.2, 239.255.255.250), Forward state - MAC not built

Feb 20 2012 22:56:08.198: MRT(0): Update (*,239.255.255.250), RPF  /0.0.0.0

Any help is really appreciated

Thanks

I have this problem too.
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mgalazka Mon, 02/20/2012 - 19:53

One quick note for you -- I have learned from experience that the 3560/3750 platform does not show accurate info for "show ip mroute count" as well as "show ip mroute active".  So if you're wondering why you show no active sources, that is likely why!

Matt

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