vlc unicast / multicasting

[merrittr]

Hi all

Im trying to work my way up testing IGMP 

right now i have a 2950 that I am using trying to uni/multicast 

from 10.50.0.1 I am running:
vlc -vvv /home/ubuntu/Downloads/bird.avi --sout udp:10.50.0.2 --ttl 12 --loop

to another port where the machine 10.50.0.2 is but the packets arent getting through

I get nothing 10.50.0.2 end using wireshark ...I am able to ping both any ideas?

[Peter Paluch]

Hi,

Well, your configuration does not seem like one that would be using multicast and thus depend on IGMP. You are using unicast addressing in your VLC. The fact you do not see anything on the 10.50.0.2 is actually strange. Can you ping between the two machines? Can you verify using Wireshark on the 10.50.0.1 (source) that the packets are being sent out?

If you want to use multicasting you need to use a destination from the 224.0.0.0/4 scope, ideally, 239.0.1.x. Avoid addresses in the form of <224-239>.{0,128}.0.x because these addresses map to the link-local MAC address scope 01:00:5E:00:00:xx which is exempted from IGMP Snooping, and you would see the switch flooding them across all ports.

In addition, if you want the switch to properly forward multicast streams only to those ports where recipients have subscribed using IGMP, you need either to have a multicast-enabled router in your network (which is probably not the case), or configure your switch to act as an IGMP Snooping Querier to send out IGMP Membership Query messages to periodically find out and refresh the location of connected receivers. The configuration would be:

enable
configure terminal
interface Vlan1
 ip address 10.50.0.254 255.255.255.0
 no shutdown
 exit
ip igmp snooping querier

Please keep us posted!

Best regards,
Peter

[merrittr]

Thanks Pete

I was dummying out when streaming from VLC got that fixed and unicast works fine .

using udp:239.1.1.1 and I entered those commands however my 2950 doesnt seem to have that last command

ip igmp snooping querier

here are my options after snooping

sw1(config)#ip igmp snooping ?
  last-member-query-interval  Last member query interval
  mrouter                     Configure multicast router detection on the
                              switch
  report-suppression          Report suppression
  source-only-learning        Source only learning configuration
  tcn                         Topology change notification configuration
  vlan                        IGMP Snooping enable for Catalyst VLAN
  <cr>

here is the version information that i have.

sw1#show version
Cisco Internetwork Operating System Software
IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(22)EA10a, RELEASE SOFTWARE (fc2)
Copyright (c) 1986-2007 by cisco Systems, Inc.
Compiled Tue 24-Jul-07 17:13 by antonino
Image text-base: 0x80010000, data-base: 0x80570000

ROM: Bootstrap program is C2950 boot loader

sw1 uptime is 5 hours, 29 minutes
System returned to ROM by power-on
System image file is "flash:/c2950-i6q4l2-mz.121-22.EA10a.bin"

cisco WS-C2950-24 (RC32300) processor (revision S0) with 20957K bytes of memory.
Processor board ID FOC1222V4FA
Last reset from system-reset
Running Standard Image
24 FastEthernet/IEEE 802.3 interface(s)

32K bytes of flash-simulated non-volatile configuration memory.
Base ethernet MAC Address: 00:21:56:6E:4F:C0
Motherboard assembly number: 73-5781-14
Power supply part number: 34-0965-01

[Peter Paluch · Accepted solution]

Hi,

Oh... I am sorry. It seems that 2950 Catalyst switches do not support the IGMP Querier function, and are thus dependent on a multicast-enabled router to send queries.

Just to make sure you have an idea what I am talking about: Catalyst switches including 2950 support a so-called IGMP Snooping feature. Basically, it is a mechanism that watches for IGMP messages coming from multicast receivers, allowing the switch to learn which station is subscribed to which multicast group. When a multicast arrives to the switch, it will be forwarded only to subscribed stations, not through all ports.

IGMP Snooping depends on receiving IGMP Membership Report messages. Here's the gotcha: stations send these messages only when initially subscribing to a multicast group, and do not repeat this message afterwards. That would cause the switch to expire the learned multicast receivers after some time. Therefore, there must be a device on the network that sends periodic IGMP Membership Query messages to elicit the Membership Report responses from the receivers. Ordinarily, the device sending Queries would be a multicast-enabled router in the network. However, in networks without such routers, 2960 and higher switches have a feature called the IGMP Snooping Querier that allows a switch to send these Membership Queries on its own, allowing it to learn and maintain accurate information about multicast receivers even without a router.

It seems, unfortunately, that this feature is not supported on 2950. Therefore, the IGMP Snooping will be unable to operate properly, and I strongly suggest deactivating it if you do not have a multicast-enabled router sending IGMP Queries in your network. Deactivating the IGMP Snooping can be done by the no ip igmp snooping command in the global config mode.

Keep in mind that the IGMP messages are primarily used between a station and its gateway (the router). The fact that switches can also intercept and process IGMP messages is an added value to switches to optimize multicast delivery, and switches can also live and operate without it.

Please feel welcome to ask further!

Best regards,
Peter

[merrittr]

Gotcha that 2950 is back on my 3 device certification heap :)

I do have another router/Switch i can use for this application its a non cisco CENTEC switch (I swapped in a L2L3 image ...it was a OpenFlow image ...ill get back to that later quite cool)

anyway the L2/L3 image uses psudo IOS commands does this look like it would do the same job as your cisco specific commands?

ip igmp snooping query-interval 100

ip igmp snooping query-max-response-time 5

ip igmp snooping last-member-query-interval 2000

ip igmp snooping vlan 1 querier address 10.50.0.254

ip igmp snooping vlan 1 querier

ip igmp snooping vlan 1 query-interval 200

ip igmp snooping vlan 1 query-max-response-time 5

ip igmp snooping vlan 1 querier-timeout 100

ip igmp snooping vlan 1 last-member-query-interval 2000

ip igmp snooping vlan 1 discard-unknown

ip igmp snooping discard-unknown

mostly I am just setting parameters there is also some talk of setting up a mrouter port. in the pdf that i have here. I shouldnt need that right if the switch dev is acting as the multicast router as set up above

[merrittr]

i added these when the above didnt fix it, I dont think I need an mrouter port since the switch itself is acting as the mcast querier

ip igmp snooping vlan 1 mrouter interface eth-0-51
ip igmp snooping vlan 1 report-suppression
ip igmp snooping vlan 1 mrouter-aging-interval 200

ip igmp snooping querier tcn query-count 5
ip igmp snooping querier tcn query-interval 20
 

I am seeing on WireShark that a query and responses occur

[merrittr]

all working using the config up above all the 239.1.1.1 addresed packets were going out the default interface due to routing fixed thats and it all works sorry to bring a competing switch in I have a c3550 on requisition to take its place

[Peter Paluch]

Hi,

No problem with the other switch.

I am not sure after your last post whether you consider this issue closed, or if there are still questions to be answered so please feel welcome to ask further.

Best regards,
Peter

[merrittr]

Yes thanks I am all good you got me going on the right track , this switch had the facility to query Ill play around with the 2950 and 3550 being the querier
 

and the 2950 mrouter

thanks Peter