IGMP Snooping Process Between Source and Receiver on Different VLANs
Host4 from a different VLAN has requested the multicast stream
239.1.1.1. (See Figure 9-6.)
A hardware shortcut is created by the MSFC in this scenario
because traffic is between different VLANs:
- Step 1. Host4, on port 1/2, sends an unsolicited IGMP membership
report to 239.1.1.1.
- Step 2. The switch intercepts the IGMP message:
MCAST-IGMPQ:recvd an IGMP V2 Report on the port 1/2 vlanNo 30 GDA
239.1.1.1
In ModifyMulticastEarlEntry
Creating new entry because it's the first Node
Creating initial node in ModifyMulticast
Updating portlist for initial hostlist add
The multicast forwarding table adds an additional line for VLAN 30 and
its associate port of 1/2 for Host4:
Switch1 (enable) show multicast group
VLAN Dest MAC/Route Des [CoS] Destination Ports or VCs/[Protocol Type]
---- ------------------ ----- --------------------------------------
3 01-00-5e-01-01-01 10/1-2,15/1
30 01-00-5e-01-01-01 1/2,15/1
- Step 3. The switch then sends the IGMP packet to the MSFC on port
15/1:
MCAST-RELAY:Relaying packet on port 15/1 vlanNo 30
MCAST-SEND: Inband Transmit Succeeded for IGMP RELAY msg on port 15/1 vlanNo 30
- Step 4. The router receives the unsolicited IGMP Join from the
receiver:
*Sep 30 09:06:58.881: IGMP: Received v2 Report on Vlan30 from 10.1.4.1 for 239.1.1.15. The
MSFC updates its IGMP membership table.
- Step 5. The router updates its IGMP membership table:
msfc_15#show ip igmp groups
IGMP Connected Group Membership
Group Address Interface Uptime Expires Last Reporter
239.1.1.1 Vlan30 00:00:46 00:02:55 10.1.4.1
- Step 6. Interface VLAN 30 is added to the OIF list. The letter H
denotes hardware switched:
msfc_15#show ip mroute 239.1.1.1
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, 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 - Advertised via MSDP, U - URD, I - Received Source Specific Host
Report
Outgoing interface flags: H - Hardware switched
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode
(*, 239.1.1.1), 00:05:45/00:02:59, RP 0.0.0.0, flags: DJC
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Vlan3, Forward/Sparse-Dense, 00:01:44/00:00:00
Vlan30, Forward/Sparse-Dense, 00:05:45/00:00:00
(10.1.3.5, 239.1.1.1), 00:00:21/00:02:59, flags: CT
Incoming interface: Vlan3, RPF nbr 0.0.0.0, RPF-MFD
Outgoing interface list:
Vlan30, Forward/Sparse-Dense, 00:00:21/00:00:00, H
- Step 7. The packets are now hardware switched between VLAN 3, the
multicast source, and VLAN 30, Host4, for 239.1.1.1 traffic:
msfc_15#show mls ip multicast group 239.1.1.1
Multicast hardware switched flows:
(10.1.3.5, 239.1.1.1) Incoming interface: Vlan3, Packets switched:
508380
Hardware switched outgoing interfaces: Vlan30
RPF-MFD installed
Total hardware switched flows : 1
An MMLS entry is created because the multicast packets are
hardware switched:
Switch1 (enable) show mls multicast entry
Router-IP Dest-IP Source-IP Pkts Bytes
InVlan Type OutVlans
--------------- --------------- --------------- -------------------- -----------
--------- ------ ---- -------------------------------------------
10.1.3.10 239.1.1.1 10.1.3.5 534751 794639986
3 C 30
Total Entries Displayed: 1 (1 complete flow (C) and 0 partial flow (P))
For the MMLS entry to be created and updated, the MMLS-route
processor (MMLS-RP), MSFC, and the MMLS-SE, the supervisor, must communicate
with each other to ensure consistent data on both devices. The show multicast statistics command displays
communication information between the MMLS-RP and MMLS-SE. (See Example 9-7.)
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