IPv6 Configuration Guide K/KA/KB.15.15

• The routing switch supports concurrent, independent operation of DHCPv4 and DHCPv6.
• Operating limits:
MaximumDHCPv6-relay feature
32
1
Unique helper addresses supported on the routing switch
32
1
Unique helper addresses per VLAN interface
1
If the same helper address is used on multiple VLANs, it is counted as one address toward these maximums.
About configuring DHCPv6 relay
Beginning with software release K.15.01, the routing switches include operation as DHCPv6 relay
agents between DHCPv6 servers and clients.
Dynamic Host Configuration Protocol (DHCPv6) is used for configuring clients with IPv6 address
and other configuration parameters without user intervention on the client. Where a DHCPv6 server
and a client exist on the same local network, the client's requests for service are received directly
by the DHCPv6 server, and a relay agent is not needed. However, if a client and the DHCPv6
server available to support it are in different networks, or subnets, a DHCPv6 relay agent is needed
to forward client service requests to the server and to relay server responses back to the client.
(The DHCPv6 relay agent is transparent to the client.)
Three main elements comprise DHCPv6-relay operation:
• DHCPv6 clients per-VLAN or subnet
• A routing switch configured with the following:
Either IPv6 static routing or the OSPFv3 routing protocol (or both)•
• DHCPv6 relay agent enabled to forward DHCPv6 client/server traffic between a host or
another relay agent and a remote DHCPv6 server
• One or more remote DHCPv6 servers reachable from the routing switch
DHCPv6 request forwarding
With DHCPv6-relay enabled and a reachable unicast helper address configured on a given VLAN,
a client request for DHCPv6 service will be routed to the designated server. If a multicast helper
address is configured on the VLAN, the client request will be sent from the routing switch on the
VLAN designated in the configuration for that helper address.
DHCPv6-relay helper addresses
A unicast helper address enables routing of a client service request to the IPv6 address of a specific,
remote DHCPv6 server.
The multicast forwarding options route DHCPv6 requests on a VLAN interface to either
• The "All_DHCP_Servers" (FF05::1:3) multicast address
• A user-selected multicast address
The routing switch supports up to 32 unique helper addresses and counts multiple instances of the
same helper address on different VLANs as one address. Where multiple helper addresses are
configured on the same VLAN, the routing switch forwards client service requests to all such
addresses, and selects the server from which it receives the first response.
General steps for enabling DHCP relay operation
For the DHCPv6 relay agent to function on the routing switch, you must complete the following
steps:
206 DHCPv6-Relay