Multicast traffic not going through

sci10270 · 08-15-2017, 12:10 AM

hello all,

I am pretty new to linux networking and linux in general.
I am trying to send multicast traffic across 2 different subnets, connected via Cisco switches.

I'm using iperf to test, so on machine A (IP 192.168.1.1) on 192.168.1.x subnet, I run the below

Code:

iperf -s -u -B 239.168.120.1 -i 1
------------------------------------------------------------
Server listening on UDP port 5001
Binding to local address 239.168.120.1
Joining multicast group  239.168.120.1
Receiving 1470 byte datagrams
UDP buffer size:  122 KByte (default)

on machine B with ip 192.168.1.2, I run the

Code:

iperf -c 239.168.120.1 -u

and I'm able to get a response. I guess because they are within the same subnet.

on machine C with ip 10.68.1.1, I run the same

Code:

iperf -c 239.168.120.1 -u

but the traffic didn't go through. Multicast seems to have been enabled on each host too. as shown below.

Code:

netstat -g
IPv6/IPv4 Group Memberships
Interface       RefCnt Group
--------------- ------ ---------------------
lo              1      all-systems.mcast.net
eth2            1      all-systems.mcast.net

ifconfig eth2
eth2      Link encap:Ethernet  HWaddr 33:33:33:33:6C:40
          inet addr:10.65.51.20  Bcast:10.65.51.255  Mask:255.255.255.0
          inet6 addr: f000::3333:bbff:fe3f:6c40/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

I've enabled multicast-routing on the Cisco switches and setup pim rp mapping.

Code:

show ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP-mapping agent

Group(s) 239.0.0.0/8
  RP 10.68.245.2 (test.net), v2v1
    Info source: 10.68.245.2 (test.net), elected via Auto-RP
         Uptime: 00:12:54, expires: 00:02:05
Group(s): 224.0.0.0/4, Static
    RP: 10.68.245.2 (test.net)

Code:

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

(*, 224.0.1.39), 01:01:43/stopped, RP 10.68.245.2, flags: SJPCLF
  Incoming interface: Vlan908, RPF nbr 10.68.245.2
  Outgoing interface list: Null

(10.65.245.2, 224.0.1.39), 00:49:43/00:02:24, flags: PLFT
  Incoming interface: Vlan908, RPF nbr 0.0.0.0
  Outgoing interface list: Null

(*, 224.0.1.40), 01:15:27/00:02:29, RP 10.68.245.2, flags: SJPCL
  Incoming interface: Vlan908, RPF nbr 10.68.245.2
  Outgoing interface list: Null

Appreciate if someone could point me in the right direction.

nini09 · 08-15-2017, 03:51 PM

You are better to setup a multicast router using Linux machine between two subnet network.

lazydog · 08-15-2017, 08:13 PM

Question but is this cisco switch doing routing?

sci10270 · 08-15-2017, 10:03 PM

Quote:

Originally Posted by nini09

You are better to setup a multicast router using Linux machine between two subnet network.

Could you please show me the ropes? Really can't thank you enough!

Quote:

Originally Posted by lazydog

Question but is this cisco switch doing routing?

Yes, it is.

nini09 · 08-16-2017, 04:50 PM

You can use igmpproxy.

lazydog · 08-16-2017, 09:43 PM

Is the switch showing multicast on the interfaces when you do a 'sh int <interface>'?

sci10270 · 08-17-2017, 04:59 AM

Quote:

Originally Posted by nini09

You can use igmpproxy.

Will spend some time to find out how that works. Thank you.

Quote:

Originally Posted by lazydog

Is the switch showing multicast on the interfaces when you do a 'sh int <interface>'?

Seems like it doesn't show. Could you explain further on how I could make this work?

#show int gi1/3
GigabitEthernet1/3 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet Port, address is xxxx
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 2/255, rxload 22/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, link type is auto, media type is 10/100/1000-TX
input flow-control is on, output flow-control is on
Auto-MDIX on (operational: off)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo

lazydog · 08-17-2017, 09:29 AM

What type of switch is this? If you are not sure run 'sh ver'.
Do you have a need for flow control to be turned on?

sci10270 · 08-17-2017, 09:31 AM

Quote:

Originally Posted by lazydog

What type of switch is this? If you are not sure run 'sh ver'.
Do you have a need for flow control to be turned on?

It's a Cisco 4948E. Not sure about flow control too.. my understanding of network is elementary, at best.

lazydog · 08-17-2017, 10:06 AM

A quick Google search tells me you have to setup multicast routing.

nini09 · 08-17-2017, 03:40 PM

Quote:

A quick Google search tells me you have to setup multicast routing.

Does it request another router to take care of PIM?

sci10270 · 08-18-2017, 02:51 AM

Quote:

Originally Posted by lazydog

A quick Google search tells me you have to setup multicast routing.

Multicast routing has been configured on the Cisco switches already.

Quote:

Originally Posted by nini09

Does it request another router to take care of PIM?

This, I'm not so sure..

Anybody ever did Multicasting end to end before on Cisco switches and Linux hosts?
Mind stating the steps down? I might have missed one or two here.