Multicasting within UCS
Qiese Dides
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1. What is Multicasting?
2. Limitations and Different Multicasting Policies
within UCS
3. Configuration of Multicast within UCS and
Upstream
4. Troubleshooting / Previous Cases
What is Multicasting?
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• Multicast is the ability to send data across a network to multiple users at
the same time (one-to-many or many-many group communication)
• Internet Group Management Protocol (IGMP) is a crucial component of
Multicast.
• The Primary purpose of IGMP is to permit hosts to communicate their
desire, to receive multicast traffic, to the IP Multicast router(s) on the
local network.
• This in return, permits the IP Multicast router(s) to “Join” The specified
multicast group and to begin forwarding the multicast traffic onto the
network segment towards the host.
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4
http://mrncciew.com/2012/12/25/igmp-basics/
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http://mrncciew.com/2012/12/25/igmp-basics/
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http://mrncciew.com/2012/12/25/igmp-basics/
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http://mrncciew.com/2012/12/25/igmp-basics/
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http://mrncciew.com/2012/12/25/igmp-basics/
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Multicast Group Addresses (224.0.0.0/4)
Range: 224.0.0.0 – 239.255.255.255
Link-Local Address Range
224.0.0.0 – 224.0.0.255
Internetwork Control Block [Predefined routing services]
224.0.1.0 – 224.0.1.255
Administratively Scoped Address Range [Private Network, If you want to use Multicast stream
recommended use these IPS]
239.0.0.0 – 239.255.255.255
First 24 bits of MAC address is replaced by a multicast specific address – 01 00 5E
25th bit is reserved
Rest 23 bits are the same as the last 23 bits of the IP address.
Hence, first 9 bits of the IP address are provided for overlapping. Out of these, first 4 are 1110.
Rest 5 bits => 25 = 32 addresses
Example:
[0100.5e][7f.2604] = [224.][127.38.4 ] (Multicast Group Address)
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Because the upper five bits of the IP multicast address are dropped in this mapping, the resulting address
is not unique. In fact, 32 different multicast group IDs map to the same Ethernet address. Network
administrators should consider this fact when assigning IP multicast addresses. For example, 224.1.1.1 and
225.1.1.1 map to the same multicast MAC address on a Layer 2 switch. If one user subscribed to Group A
(as designated by 224.1.1.1) and the other users subscribed to Group B (as designated by 225.1.1.1), they
would both receive both A and B streams. This situation limits the effectiveness of this multicast
deployment.
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• IGMP snooping allows a Layer 2 switch to dynamically determine which
hosts connected to a particular VLAN in the switch need to receive a
particular multicast transmission. This is done by snooping or listening in
and inspecting on IGMP membership reports.
• In the absence of an upstream multicast router, enabling IGMP snooping
querier allows a Layer 2 switch to send IGMP queries to the host (in
place of the Multicast Router) so that the multicast membership is kept
up to date on the switch.
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UCS Limitations and Multicast
Configurations
Special Thanks to Michael Petrinovic ~
NPI Power Point..
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• Multicast on the UCS have IGMP snooping enabled by default
and this can not be disabled. (You could disable via the
debug)
• The UCS Fabric Interconnects have no IGMP querier
functionality this requires you to enable the querier
functionality on a device in the upstream L2 network.
• For this to work you need the following:
Multicast Router in the VLAN or IGMP querier in the VLAN.
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• By default, IGMP snooping is enabled. Network administrators
should carefully examine any requirements to disable IGMP
snooping and the detrimental performance that might be
experienced.
• IGMP Snooping configuration is only available and configurable
on a per VLAN basis. You cannot enable/disable IGMP Snooping
globally
• Disabling of IGMP snooping is supported in both End Host Mode
(EHM) and Switch Mode
• No support for Multicast Policies on network groups (another new
feature in Del Mar)
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• For a 6100 series Fabric Interconnect (FI), all VLANs can only
use the default multicast policy. However, the user can modify the
IGMP snooping/querier states of this default policy. Configuring
any other multicast policy will throw an error
• The changing of the multicast policy for a particular VLAN
(to something other than the default multicast policy) is only
supported on 6200 FIs and NOT on 6100s. The reason that
the 6100 FIs cannot have different multicast policies on its
VLANs is due to a limitation in the Gatos ASIC. This
limitation does not exist on the 6200 FIs with Carmel ASICs
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IGMP Snooping Enabled / IGMP Querier Enabled
•
Will only send the queries to the blades. Will not send IGMP queries to the upstream network
•
The FIs don’t send the IGMP queries to the upstream switch as this contradicts the role of End Host
mode in the network. This can lead to unwanted multicast traffic (both control and data) being sent to
the FIs. This is the reason why it was decided to have EHM FIs be responsible for sending IGMP
queries down to its blades only.
•
As a result, require one of the following to be configured:
1.
Configure IGMP querier on upstream switch with IGMP snooping enabled; or
2.
Disable IGMP snooping on upstream switch to flood mcast traffic; or
3.
Alternatively, change the FIs to switch mode
IGMP Snooping Enabled / IGMP Querier Disabled
•
Default mode, same as pre Del Mar release
•
Requires either:
1.
IGMP Querier in the upstream switch for the VLAN with IGMP snooping enabled; or
2.
Multicast router in the VLAN
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IGMP Snooping Disabled / IGMP Querier Disabled
• FIs will flood multicast traffic in the VLAN
• Requires one of the following to work successfully:
1.
Upstream switch can have IGMP snooping enabled or
2.
alternatively have it disabled on the upstream switch to flood multicast traffic
IGMP Snooping Disabled / IGMP Querier Enabled
• This is not a valid configuration
• This is correctly blocked by the UCSM
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IGMP Snooping Enabled / IGMP Querier Enabled
• FIs will forward IGMP queries to the upstream network
• Upstream switches will learn of IGMP querier configured on FIs, will then build and forward
mcast traffic towards FIs
• Requires either:
1.
Upstream switch can have IGMP snooping enabled or
2.
alternatively have it disabled to flood multicast traffic
IGMP Snooping Enabled / IGMP Querier Disabled
• Default mode, same as pre Del Mar release
• Requires either:
1.
IGMP Querier in the upstream switch for the VLAN with IGMP snooping enabled; or
2.
Multicast router in the VLAN
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IGMP Snooping Disabled / IGMP Querier Disabled
• FIs will flood multicast traffic in the VLAN
• Requires either:
1.
Upstream switch can have IGMP snooping enabled or
2.
alternatively have it disabled to flood multicast traffic
IGMP Snooping Disabled / IGMP Querier Enabled
• This is not a valid configuration
• This is correctly blocked by the UCSM
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UCS and Upstream
Configuration
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• IGMP snooping is available on VLAN basis and not on interface
level. From UCSM, this can be configured by referring to a
Multicast Policy on a named Vlan.
1.
2.
3.
4.
Add a new “Multicast Policies” node under LAN -> LAN-> Policies -> root
Support for creation/modification/deletion of Multicast Policies
Option for selecting existing Multicast policy when a VLAN is created.
Support for attaching an existing Multicast policy with a VLAN which is
already created
• Multicast Policies are only under the root policies tree and you
cannot create individual policies under a sub-organization
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• Default multicast policy keeps in line with Fabric Interconnect
behaviour prior to 2.1 Del Mar release:
IGMP Snooping – Enabled
IGMP Querier - Disabled
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• Add a new “Multicast Policies” node under LAN -> LAN-> Policies -> root
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• Right Click on Multicast Policies, then “Create Multicast Policy”
• Presented with the following
• Provide a Name and configure the IGMP Snooping and Snooping
Querier states
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• If you attempt to have IGMP Snooping disabled while having the IGMP
Snooping Querier enabled, this will throw an error, as this isn’t a valid
configuration
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• When creating a new VLAN, now additionally have option to specify
Multicast Policy Name
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• Examples with different policies set on the VLAN
• Multicast Policy Name is what you have configured where Multicast
Policy Instance is what is actually being used by the Fabric
Interconnects
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• If you create multiple VLAN objects, which point to the same VLAN ID, when you apply a
Multicast policy, it will be applied to all VLAN objects with the same VLAN ID. The latest
Multicast policy applied is applied to all. Eg: QMulticast changed to Snoop_off_qu_off
(Vlan 38)
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• Add a new command to create multicast policy under scope org.
MiniMe-B# scope org
MiniMe-B /org # create mcast-policy <name>
• Set properties for multicast policy
MiniMe-B /org/mcast-policy #set querier <enable/disable>
MiniMe-B /org/mcast-policy #set snooping <enable/disable>
• New command to view existing multicast policies.
MiniMe-B # scope org
MiniMe-B /org # show mcast-policy
• New command to delete existing multicast policy.
MiniMe-B # scope org
MiniMe-B /org # delete mcast-policy <name>
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• When creating a VLAN, user allowed to add an existing
multicast policy to the VLAN
MiniMe-B# scope eth-uplink
MiniMe-B /eth-uplink # scope vlan <vlan>
MiniMe-B /eth-uplink/vlan # set mcastpolicy <name>
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• When creating a VLAN, user allowed to add an existing
multicast policy to the VLAN
MiniMe-B# scope eth-uplink
MiniMe-B /eth-uplink # scope vlan <vlan>
MiniMe-B /eth-uplink/vlan # set mcastpolicy <name>
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• On the upstream switch you must configure the igmp snooping
querier on a specific VLAN and the igmp snooping querier must
match the IP in the UCS multicast policy.
• AGR012-5K-A(config)# vlan 38
• AGR012-5K-A(config-vlan)# vlan configuration 38
• AGR012-5K-A(config-vlan-config)# ip igmp snooping querier
172.16.38.124
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Troubleshooting / Previous
Cases
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• Show ip igmp snooping vlan <vlan id> [This can be done on either
the Upstream switch or Fabric Interconnect]
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• Show ip igmp snooping querier vlan <vlan id> [This can be done
on either the Upstream switch or Fabric Interconnect]
• Show ip igmp snooping groups vlan <vlan id> [This can be done
on either the Upstream switch or Fabric Interconnect]
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• Show ip igmp snooping statistics vlan <vlan id> [This can be done
on either the Upstream switch or Fabric Interconnect]
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• AGR012-5K-A# show mac address-table multicast
Legend:
- primary entry, G - Gateway MAC, (R) - Routed MAC, O - Overlay MAC age - seconds since last seen,+ primary entry using vPC Peer-Link
VLAN
MAC Address
Type
age
Secure NTFY
Ports
---------+-----------------+--------+---------+------+----+-----------------38
0100.5e10.2604
38
0100.5e7f.fffd
igmp
igmp
0
0
F
F
F Eth1/2 Router
F Eth1/2 Router
0100.5e7f.2604 = 224.127.38.4 (Multicast Group Address)
0100.5e7f.fffd = 224.127.255.253 (Multicast Group Address)
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• AGR012-5K-A# ethanalyzer local interface inbound-low display-filter igmp
limit
- This does not capture actual video stream data, just IGMP data. This tool will capture
control traffic. (EX; it shows when a host joins or leaves the group.
Capturing on inband
2009-12-02 02:11:34.435559 172.16.38.5 -> 224.0.0.22 IGMP V3 Membership Report / Join group 224.0.0.252 for any
sources
2009-12-02 02:11:55.416507 172.16.38.6 -> 224.0.0.22 IGMP V3 Membership Report / Leave group 236.16.38.4
2009-12-02 02:11:55.802408 172.16.38.6 -> 224.0.0.22 IGMP V3 Membership Report / Leave group 236.16.38.4
2009-12-02 02:11:59.378576 172.16.38.6 -> 224.0.0.22 IGMP V3 Membership Report / Join group 236.16.38.4 for any
sources
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• UDPCAST (http://www.udpcast.linux.lu/cmd.html)
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• UDPCAST (http://www.udpcast.linux.lu/cmd.html)
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•
VLC (http://www.videolan.org/vlc/index.html)
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•
623539901
Reported problem: Customer has esx hosts where multicast works when all the virtual machines are on the same
host, if they separate virtual machines on different hosts then multicast stops working
Solution: IGMP querier needed to be configured upstream on VLAN 5
623539901
Reported problem: Customer experiencing problems with multicast traffic between two B200M2 blades in the same chassis
Solution: Customer was incorrectly using reserved multicast addresses & IGMP querier needed to be configured upstream
626082965
Reported problem: Customer is trying to create multicast policy in UCS for a specific VLAN and receiving an error stating only
default Multicast Policy is supported
Solution: Multicast policy on 6100 series FI is applied to all VLANs, customer needed a 6200 to specify multicast policy on
individual vlans
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•
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•
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http://en.wikipedia.org/wiki/Multicast
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli
_rel_4_0_1a/CLIConfigurationGuide/QoS.html
https://techzone.cisco.com/t5/B-Series/Troubleshooting-Multicast-on-UCS-and-Nexus-1000v/tap/454663
https://techzone.cisco.com/t5/B-Series/Del-Mar-UCS-IGMP-Snooping-and-Querier/ta-p/106748
https://techzone.cisco.com/t5/B-Series/Q-amp-A-Multicast-failover-and-Best-Practices-inUCS/ta-p/163514
https://techzone.cisco.com/t5/B-Series/Multicast-Can-Cause-MAC-Flapping-with-UCS-in-EndHost-Mode/ta-p/684859
https://techzone.cisco.com/t5/General-Knowledge-Base/UCS-2-0-Networking-ConfigurationLimits/ta-p/251020
https://techzone.cisco.com/t5/C10K-Router/Multicast-Troubleshooting-Guide/ta-p/219766
https://techzone.cisco.com/t5/Multicast/Summary-IGMP-v1-v2-and-v3-messages-timers-andcontrol-IPs/ta-p/128932
https://techzone.cisco.com/t5/B-Series/FI-6248-6296-Mapping-QoS-groups-to-internal-classesand-buffer/ta-p/732375
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Thank you.