Dell SmartFabric OS10 User Guide Release 10.5.3

Intermediate switch deployed between DHCPv6 client and the DHCPv6 relay agent

If your deployment includes an intermediate switch between the DHCP client and the DHCP relay agent, messages from the client might not reach the server.

In this example, the client sends a request for an IPv6 address to the DHCP server. The request is sent through the L2 switch, the Relay Agent, and then to the DHCP server. The server processes the request.

In OS10, the MLD snooping and the Unknown Multicast Flood Control feature are enabled by default. Hence, all the unknown multicast packets are dropped. In this case, the DHCPv6 solicit message is considered an unknown multicast packet and is dropped.

For the DHCPv6 solicit messages to reach the DHCP server:

1. On the intermediate switch (L2 switch), you must do one of the following:
   • Disable multicast snooping flood-restrict globally.

     L2switch(config)# no multicast snooping flood-restrict

   • Configure the specific VLAN interface as a multicast router interface using the ipv6 mld snooping mrouter command.

     L2switch(config)# interface vlan 10
     L2switch(conf-if-vl-10)# ipv6 mld snooping mrouter interface ethernet 1/1/51
     L2switch(conf-if-vl-10)# ipv6 mld version 2
     L2switch(conf-if-vl-10)# ipv6 mld snooping query-interval 60
     L2switch(conf-if-vl-10)# ipv6 mld snooping query-interval 130
     L2switch(conf-if-vl-10)# ipv6 mld snooping query-max-resp-time 10
     L2switch(conf-if-vl-10)# ipv6 mld snooping last-member-query-interval 1000
     L2switch(conf-if-vl-10)# exit

   • Disable MLD snooping on the specific VLAN interface.

     L2switch(config)# interface vlan 10
     L2switch(conf-if-vl-10)# no shutdown
     L2switch(conf-if-vl-10)# no ipv6 mld snooping enable

   • Disable MLD snooping globally.

     L2switch(config)# no ipv6 mld snooping enable
     

2. On the relay agent, enable MLD querier on the specific VLAN interface.

   L2switch(config)# interface vlan 10
   L2switch(conf-if-vl-10)# ipv6 mld version 2
   L2switch(conf-if-vl-10)# ipv6 mld snooping query-interval 60
   L2switch(conf-if-vl-10)# ipv6 mld snooping query-interval 130
   L2switch(conf-if-vl-10)# ipv6 mld snooping query-max-resp-time 10
   L2switch(conf-if-vl-10)# ipv6 mld snooping last-member-query-interval 1000
   L2switch(conf-if-vl-10)# exit

   RA(config)# interface vlan 10
   RA(conf-if-vl-10)# ipv6 address 3::1/64
   RA(conf-if-vl-10)# ipv6 mld snooping querier
   RA(conf-if-vl-10)# ipv6 helper-address 3::3
   RA(conf-if-vl-10)# ipv6 mld version 2
   RA(conf-if-vl-10)# ipv6 mld snooping query-interval 60
   RA(conf-if-vl-10)# ipv6 mld snooping query-interval 130
   RA(conf-if-vl-10)# ipv6 mld snooping query-max-resp-time 10
   RA(conf-if-vl-10)# ipv6 mld snooping last-member-query-interval 1000