Verifying MLD Snooping on EX Series Switches (CLI Procedure)
Multicast Listener Discovery (MLD) snooping constrains the flooding of IPv6 multicast traffic on VLANs on a switch. This topic describes how to verify MLD snooping operation on the switch.
Verifying MLD Snooping Memberships
Purpose
Determine group memberships, multicast-router interfaces, host MLD versions, and the current values of timeout counters.
Action
Enter the following command:
user@switch> show mld snooping membership detail
VLAN: mld-vlan Tag: 100 (Index: 3)
Router interfaces:
ge-1/0/0.0 dynamic Uptime: 00:14:24 timeout: 253
Group: ff1e::2010
ge-1/0/30.0 Timeout: 180 Flags: <V2-hosts>
Last reporter: fe80::2020:1:1:3
Include source: 2020:1:1:1::2
Include source: 2020:1:1:1::5
Meaning
The switch has multicast membership information for one VLAN on the switch, mld-vlan. MLD snooping might be enabled on other VLANs, but the switch does not have any multicast membership information for them. The following information is provided:
Information on the multicast-router interfaces for the VLAN—in this case, ge-1/0/0.0. The multicast-router interface has been learned by MLD snooping, as indicated by dynamic. The timeout value shows how many seconds from now the interface will be removed from the multicast forwarding table if the switch does not receive MLD queries or Protocol Independent Multicast (PIM) updates on the interface.
Information about the group memberships for the VLAN:
Currently, the VLAN has membership in only one multicast group, ff1e::2010.
The host or hosts that have reported membership in the group are on interface ge-1/0/30.0. The interface group membership will time out in 180 seconds if no hosts respond to membership queries during this interval. The flags field shows the lowest version of MLD used by a host that is currently a member of the group, which in this case is MLD version 2 (MLDv2).
The last host that reported membership in the group has address fe80::2020:1:1:3.
Because interface has MLDv2 hosts on it, the source addresses from which the MLDv2 hosts want to receive group multicast traffic are shown (addresses 2020:1:1:1::2 and 2020:1:1:1::5). The timeout value for the interface group membership is derived from the largest timeout value for all sources addresses for the group.
Verifying MLD Snooping VLANs
Purpose
Verify that MLD snooping is enabled on a VLAN and display MLD snooping information for each VLAN on which MLD snooping is enabled.
Action
Enter the following command:
user@switch> show mld-snooping vlans detail
VLAN: v10, Tag: 10
Interface: ge-1/0/0.0, tagged, Groups: 0, Router
Interface: ge-1/0/30.0, untagged, Groups: 1
Interface: ge-12/0/30.0, untagged, Groups: 0
VLAN: v20, Tag: 20
Interface: ge-1/0/0.0, tagged, Groups: 0, Router
Interface: ge-1/0/31.0, untagged, Groups: 0
Interface: ge-12/0/31.0, untagged, Groups: 1Meaning
MLD snooping is configured on two VLANs on the switch: v10 and v20. Each interface in each VLAN is listed and the following information is provided:
Whether the interface is a trunk (tagged) or access (untagged) interface.
How many multicast groups the interface belongs to.
Whether the interface is a multicast-router interface (Router).
Viewing MLD Snooping Statistics
Purpose
Display MLD snooping statistics, such as number of MLD queries, reports, and leaves received and how many of these MLD messages contained errors.
Action
Enter the following command:
user@switch> show mld snooping statistics
Bad length: 0 Bad checksum: 0 Invalid interface: 0
Not local: 0 Receive unknown: 0 Timed out: 0
MLD Type Received Transmitted Recv Errors
Queries: 74295 0 0
Reports: 18148423 0 16333523
Leaves: 0 0 0
Other: 0 0 0
Meaning
The output shows how many MLD messages of each type—Queries, Reports, Leaves—the switch received or transmitted on interfaces on which MLD snooping is enabled. For each message type, it also shows the number of MLD packets the switch received that had errors—for example, packets that do not conform to the MLDv1 or MLDv2 standards. If the Recv Errors count increases, verify that the hosts are compliant with MLDv1 or MLDv2 standards. If the switch is unable to recognize the MLD message type for a packet, it counts the packet under Receive unknown.
Viewing MLD Snooping Routing Information
Purpose
Display the next-hop information maintained in the multicast forwarding table.
Action
Enter the following command:
user@switch> show mld-snooping route detail
VLAN Group Next-hop
mld-vlan ::0000:2010 1323
Interfaces: ge-1/0/30.0, ge-1/0/33.0
VLAN Group Next-hop
mld-vlan ff00:: 1317
Interfaces: ge-1/0/0.0, ge-1/0/33.0
VLAN Group Next-hop
mld-vlan ::0000:0000 1317
Interfaces: ge-1/0/0.0
VLAN Group Next-hop
mld-vlan1 ::0000:2010 1324
Interfaces: ge-12/0/31.0
VLAN Group Next-hop
mld-vlan1 ff00:: 1318
Interfaces: ae200.0
VLAN Group Next-hop
mld-vlan1 ::0000:0000 1318
Interfaces: ae200.0Meaning
The output shows the next-hop interfaces for a given multicast group on a VLAN. Only the last 32 bits of the group address are shown because the switch uses only these bits in determining multicast routes. For example, route ::0000:2010 on mld-vlan has next-hop interfaces ge-1/0/30.0 and ge-1/0/33.0.