Verifying MLD Snooping on Switches
This topic uses Junos OS with support for the Enhanced Layer 2 Software (ELS) configuration style. If your switch runs software that does not support ELS, see Verifying MLD Snooping on EX Series Switches (CLI Procedure). For ELS details, see Using the Enhanced Layer 2 Software CLI.
Multicast Listener Discovery (MLD) snooping constrains the flooding of IPv6 multicast traffic on VLANs. This topic describes how to verify MLD snooping operation on a VLAN.
Verifying MLD Snooping Memberships
Purpose
Verify that MLD snooping is enabled on a VLAN and determine group memberships.
Action
Enter the following command:
user@switch> show mld snooping membership detail
Instance: default-switch
Vlan: v1
Learning-Domain: default
Interface: ge-0/0/1.0, Groups: 1
Group: ff05::1
Group mode: Exclude
Source: ::
Last reported by: fe80::
Group timeout: 259 Type: Dynamic
Interface: ge-0/0/2.0, Groups: 0Meaning
The switch has multicast membership information for one VLAN on the switch, v1. 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 about the group memberships for the VLAN:
Currently, the VLAN has membership in only one multicast group,
ff05::1.The host or hosts that have reported membership in the group are on interface ge-0/0/1.0.
The last host that reported membership in the group has address
fe80::.The interface group membership will time out in
259seconds if no hosts respond to membership queries during this interval.The group membership has been learned by MLD snooping, as indicated by
Dynamic.
Verifying MLD Snooping Interfaces
Purpose
Display MLD snooping information for each interface on which MLD snooping is enabled.
Action
Enter the following command:
user@switch>show mld snooping interface
Instance: default-switch
Vlan: v100
Learning-Domain: default
Interface: ge-0/0/1.0
State: Up Groups: 1
Immediate leave: Off
Router interface: no
Interface: ge-0/0/2.0
State: Up Groups: 0
Immediate leave: Off
Router interface: no
Configured Parameters:
MLD Query Interval: 125.0
MLD Query Response Interval: 10.0
MLD Last Member Query Interval: 1.0
MLD Robustness Count: 2Meaning
MLD snooping is configured on one VLAN on the switch, v100. Each interface in each VLAN is listed and the following information is provided:
How many multicast groups the interface belongs to.
Whether immediate leave has been configured for the interface.
Whether the interface is a multicast-router interface.
The output also shows the configured parameters for the MLD querier.
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 Vlan: v1 MLD Message type Received Sent Rx errors Listener Query (v1/v2) 0 4 0 Listener Report (v1) 447 0 0 Listener Done (v1/v2) 0 0 0 Listener Report (v2) 0 0 0 Other Unknown types 0 Vlan: v2 MLD Message type Received Sent Rx errors Listener Query (v1/v2) 0 4 0 Listener Report (v1) 154 0 0 Listener Done (v1/v2) 0 0 0 Listener Report (v2) 0 0 0 Other Unknown types 0 Instance: default-switch MLD Message type Received Sent Rx errors Listener Query (v1/v2) 0 8 0 Listener Report (v1) 601 0 0 Listener Done (v1/v2) 0 0 0 Listener Report (v2) 0 0 0 Other Unknown types 0 MLD Global Statistics Bad Length 0 Bad Checksum 0 Bad Receive If 0 Rx non-local 0 Timed out 0
Meaning
The output shows how many MLD messages of each type—Queries, Done, Report—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 Rx 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 Other Unknown types.
Viewing MLD Snooping Routing Information
Purpose
Display the next-hop information maintained in the multicast snooping forwarding table.
Action
Enter the following command:
user@switch>show multicast snooping route
Nexthop Bulking: OFF
Family: INET6
Group: ff00::/8
Source: ::/128
Vlan: v1
Group: ff02::1/128
Source: ::/128
Vlan: v1
Downstream interface list:
ge-1/0/16.0
Group: ff05::1/128
Source: ::/128
Vlan: v1
Downstream interface list:
ge-1/0/16.0
Group: ff06::1/128
Source: ::/128
Vlan: v1
Downstream interface list:
ge-1/0/16.0Meaning
The output shows the next-hop interfaces for a given multicast group on a VLAN.
For example, route ff02::1/128 on VLAN v1 has the next-hop interface ge-1/0/16.0.