multicast packets dropped

I have Catalyst 3560 connected to end host recieving multicast traffic. RPF and other checks in the network are fine. Inbound interface shows ~100 pkts/sec, without signs of dropping, yet outbound interface connected to end host shows output of ~20 pkts/sec. Why are packets being "swallowed" by switch, and what show commands can I use to see what's happening? I should mention that both of my interfaces are beloning to separate vrf, but i don't think that matters.

 

SW1#sh int f0/23
FastEthernet0/23 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0011.5c68.eec3 (bia 0011.5c68.eec3)
Internet address is 10.21.22.1/24
MTU 1504 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:03, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
30 second input rate 738000 bits/sec, 91 packets/sec
30 second output rate 0 bits/sec, 0 packets/sec
11670 packets input, 11837149 bytes, 0 no buffer
Received 11603 broadcasts (11417 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 11603 multicast, 0 pause input
0 input packets with dribble condition detected
96 packets output, 10075 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out


SW1#sh int f0/2
FastEthernet0/2 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0011.5c68.eec2 (bia 0011.5c68.eec2)
Internet address is 10.21.21.254/24
MTU 1504 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
30 second input rate 0 bits/sec, 0 packets/sec
30 second output rate 146000 bits/sec, 17 packets/sec
255 packets input, 62332 bytes, 0 no buffer
Received 245 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 169 multicast, 0 pause input
0 input packets with dribble condition detected
3271 packets output, 3249185 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out

Comments

  • Anyone have an idea where to even start troubleshooting?

  • Does unicast work okay?

    Brian McGahan, CCIE #8593 (R&S/SP/Security)
     
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    On Aug 21, 2011, at 4:41 PM, "ccierating" <[email protected]> wrote:

    Anyone have an idea where to even start troubleshooting?




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  • Yes unicast works; Are there any show commands that will point out to why aren't packets forwarded across interfaces?

    #debug ip mpacket shows pakets are forwarded but obviously most aren;t.

    Thx

  • Are you saying multicast traffic reaches the switch which does not forward it outbound to multicast receivers? Do you have real hosts/multicast receivers? Have they correctly joined the multicast group "show ip igmp groups"? Check mac address table for the OIL, is the switch forwarding for the multicast mac address? try configuring an inbound ACL on the switch (incoming multicast interface) to see if multicast traffic reaches the switch.

    Good luck with your studies!

  • The switch has real win7 host connected to port f0/2 and it joined group to recieve VLC stream over network, Everything works fine, traffic comes to switch over network, but then the swith for some reason throttles or swallows some of the input rate on multicast packets. If you check interface f0/23 - inbound interface, and interface f0/2 - outbound connected to win7 host, you'll see huge difference to number of packets passing trough switch. There is no other configuration that would throttle packet ouput, and this only happens with multicast, not unicast. Tried this with two 3560 I have and its same thing, so i doubt they are both faulty in same way.

  • If you used two different switches running two different IOS versions, i doubt you could hit the same "feature". It may be related to your config. Did you try to make the switch static join the multicast group and see if behavior is the same? Then issue some pings to that multicast address from the subnet of the source and see if the switch responds.

    Good luck with your studies!

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