Users Guide

DHCP relay agent
A DHCP relay agent relays DHCP messages to and from a remote DHCP server, even if the client and server are on different IP
networks. You can configure the IP address of the remote DHCP server.
You can configure a device either as a DHCP server or a DHCP relay agent — but not both.
If routes are not leaked between VRFs, the DHCP relay agent supports multi-virtual routing and forwarding (VRF) instances.
The client-facing and server-facing interfaces must be in the same VRF.
NOTE: DHCP relay implementation supports IPv4 and IPv6 addresses.
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
System management
265