Stateful DHCPv6 Relay Configuration Example

Sivagami Narayanan · ‎11-27-2012

Introduction

This document discuss with an example how to configure Stateful DHCPv6 in Relay mode. Mostly, while configuring the DHCP, the DHCP server may not be connected to clients directly in practical scenarios due to management reasons.In such cases, a DHCP relay agent serves the purpose relaying the messages coming from the clients and server.The DHCPv6 Relay Agent uses Relay forward/Reply messages to relay the messages between Servers and clients.

Requirements

Understanding of IPv6 Addressing Scheme
Implementing DHCPv6 - An Introduction

Background

In this configuration example,the router R1 is configured as DHCPv6 server and R2 is configured as Relay Agent. The routers R3 and R4 are configured as DHCPv6Client.

Note: All configurations are tested in a lab environment involving ASR 1000 series router as DHCP server and Cisco 2800 series router as DHCP Clients.

Topology Diagram

Summary Steps

Server Configuration

In Global Configuration Mode

ipv6 unciast-routing
ipv6 dhcp pool <pool name>
address prefix <specify address prefix> lifetime <infinite> <infinite>
dns-server <specify the dns server address>
domain-name <specify the domain name>
exit

In Interface Configuration Mode

ipv6 address <specify IPv6 Address>
ipv6 dhcp server <server name>rapid-commit

Relay Agent Configuration

In Global Configuration Mode

enable
configure terminal
ipv6 unicast-routing

In Interface Configuration Mode

In DHCPv6 server Facing Interface:

ipv6 address autoconfig
ipv6 enable
exit

In Clients Facing Interface

ipv6 address <specify IPv6 address>
ipv6 dhcp relay destination <specify destination IPv6 address><interface type>

Note: Specify a destination address to which client packets are forwarded and enables DHCPv6 relay service on the interface.

Client Configuration

In Global Configuration Mode

enable
configure terminal
ipv6 unicast-routing
ipv6 nd route-owner

In Interface Configuration Mode

ipv6 address dhcp rapid commit
ipv6 enable
ipv6 nd autoconfig prefix
ipv6 nd autoconfig default-route
exit

Configuration

DHCPv6 ServerDHCPv6 Relay Agent
DHCPv6 Client

!
version 15.0
!
hostname R1
!
ipv6 unicast-routing
ipv6 cef
ipv6 dhcp pool test
address prefix 2001:DB8:11::/64 lifetime infinite infinite
dns-server AAAA:BBBB:FE10::100
dns-server 2001:DB8::5
domain-name example.com
!
!
!
interface FastEthernet1/0
no ip address
duplex auto
speed auto
ipv6 address 2001:DB8:10::1/64
ipv6 dhcp server test
!
!
!
ipv6 route 2001:DB8:11::/64 2001:DB8:10:0:C804:1AFF:FEAC:1C
!
!
end

!
version 15.0
!
hostname R2
!
ipv6 unicast-routing
ipv6 cef
!
!
interface FastEthernet1/0
no ip address
duplex auto
speed auto
ipv6 address autoconfig
ipv6 enable
!
!
interface FastEthernet1/1
no ip address
duplex auto
speed auto
ipv6 address 2001:DB8:11::2/64
ipv6 enable
ipv6 dhcp relay destination 2001:DB8:10::1 FastEthernet1/0
!
!
!
end

!
version 15.0
!
hostname R3/hostname R4
!
ipv6 nd route-owner
ipv6 unicast-routing
ipv6 cef
!
!
interface FastEthernet1/0
no ip address
duplex auto
speed auto
ipv6 address dhcp rapid-commit
ipv6 enable
ipv6 nd autoconfig prefix
ipv6 nd autoconfig default-route
!
!
!
end

Note:

Static route to reach the clients (client prefix 2001:db8:11::/64) is added in the DHCPv6 Server so that it can reach clients
Under Client configuration

The command ipv6 nd route-owner inserts Neighbor Discovery-learned routes into the routing table with "ND" status and enables ND autoconfiguration behavior.This command is configured in Global Configuration mode.

Enabling the command ipv6 nd autoconfig prefix in the interface configuration mode, uses Neighbor Discovery to install all valid on-link prefixes from RAs received on the interface.

To allow Neighbor Discovery to install a default route to the Neighbor Discovery-derived default router, use the command ipv6 nd autoconfig default-route in the interface configuration mode

Verify Commands

show ipv6 route

In client routers R3 and R4 default route is installed for the ND derived default router.Use this command show ipv6 route to check the routing table.

R3#show ipv6 route
IPv6 Routing Table - default - 5 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
       B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       D - EIGRP, EX - EIGRP external, ND - Neighbor Discovery
       O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
ND ::/0 [2/0]
     via FE80::C804:1AFF:FEAC:1D, FastEthernet1/0
ND 2001:DB8:11::/64 [2/0]
     via FastEthernet1/0, directly connected
LC 2001:DB8:11:0:209E:3F6C:3900:7602/128 [0/0]
     via FastEthernet1/0, receive
ND 2001:DB8:11:0:F145:5C6F:3658:7DB6/128 [2/0]
     via FastEthernet1/0, directly connected
L   FF00::/8 [0/0]
     via Null0, receive

show ipv6 dhcp pool

To display the DHCPv6 pool information, in the DHCPv6 server use this command. The output shows that the number of active clients is 2 and also displays other configuration parameter information, such as domain name server address and preferred life time information.

R1#show ipv6 dhcp pool
DHCPv6 pool: test
Address allocation prefix: 2001:DB8:11::/64 valid 4294967295 preferred 4294967295 (2 in use, 0 conflicts)
DNS server: AAAA:BBBB:FE10::100
DNS server: 2001:DB8::5
Domain name: example.com
Active clients: 2

show ipv6 dhcp binding

To display the information information about the clients, which includes their DUIDs, IAPDs, prefixes, and preferred and valid lifetimes.

R1#sh ipv6 dhcp bin
Client: FE80::C805:FFF:FE84:1C
DUID: 00030001CA050F840000
Username : unassigned
IA NA: IA ID 0x00040001, T1 43200, T2 69120
    Address: 2001:DB8:11:0:F145:5C6F:3658:7DB6
            preferred lifetime INFINITY, , valid lifetime INFINITY,
Client: FE80::C806:FFF:FE84:1C
DUID: 00030001CA060F840000
Username : unassigned
IA NA: IA ID 0x00040001, T1 43200, T2 69120
    Address: 2001:DB8:11:0:209E:3F6C:3900:7602
            preferred lifetime INFINITY, , valid lifetime INFINITY,

show ipv6 dhcp interface

This command shows that interface Fa1/1 is configured in Relay Mode and displays the relay destination to which messages from clients should be forwarded.

R2#show ipv6 dhcp interface
FastEthernet1/1 is in relay mode
Relay destinations:
2001:DB8:10::1 via FastEthernet1/0

The configuration on the client's side can be verified using the same command in router R3 and R4.

R4#show ipv6 dhcp interface
FastEthernet1/0 is in client mode
Prefix State is IDLE
Address State is OPEN
Renew for address will be sent in 06:26:48
List of known servers:
    Reachable via address: FE80::C804:1AFF:FEAC:1D
    DUID: 00030001CA031AAC0000
    Preference: 0
    Configuration parameters:
      IA NA: IA ID 0x00040001, T1 43200, T2 69120
        Address: 2001:DB8:11:0:F145:5C6F:3658:7DB6/128
                preferred lifetime INFINITY, valid lifetime INFINITY
      DNS server: AAAA:BBBB:FE10::100
      DNS server: 2001:DB8::5
      Domain name: example.com
      Information refresh time: 0
Prefix Rapid-Commit: disabled
Address Rapid-Commit: disabled

R3#show ipv6 dhcp interface
FastEthernet1/0 is in client mode
Prefix State is IDLE
Address State is OPEN
Renew for address will be sent in 06:11:30
List of known servers:
    Reachable via address: FE80::C804:1AFF:FEAC:1D
    DUID: 00030001CA031AAC0000
    Preference: 0
    Configuration parameters:
      IA NA: IA ID 0x00040001, T1 43200, T2 69120
        Address: 2001:DB8:11:0:209E:3F6C:3900:7602/128
                preferred lifetime INFINITY, valid lifetime INFINITY
      DNS server: AAAA:BBBB:FE10::100
      DNS server: 2001:DB8::5
      Domain name: example.com
      Information refresh time: 0
Prefix Rapid-Commit: disabled
Address Rapid-Commit: enabled

Ping

You can check the connectivity between the DHCPv6 server and Clients using the ping command

R1#ping 2001:DB8:11:0:209E:3F6C:3900:7602 (Pinging Client 1 R3 from DHCPv6 Server)

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:11:0:209E:3F6C:3900:7602, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/66/120 ms

R1#ping 2001:DB8:11:0:F145:5C6F:3658:7DB6(Pinging Client 2 R4 from DHCPv6 Server)

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:11:0:F145:5C6F:3658:7DB6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0/113/400 ms

Now ping the DHCPv6 server address from the clients R3 and R4.

R3#ping 2001:db8:10::1 (DHCPv6 server Fa1/0 Interface IPv6 address)

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:10::1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/48/168 ms

R4#ping 2001:db8:10::1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:10::1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/80/140 ms

References

Routing Information Protocol

jd219 · ‎08-29-2017

very good explanation.

rrsstefano · ‎03-22-2022

Hi, very interesting.

One question : if I'm not wrong, in this setup dhcp server is releasing only dns address and domain name, while addres is get by the client through nd from the router.

I'm trying to test an environment where dhcp offer also the ipv6 address to the client but for now it is not working.

Do you have a similar setup to share ?

thanks

Stefano

bintangprimadata · ‎12-12-2023

May i have the file? Or if possible, can you send the file to my email? or send the download link by replying to my comment

Thanks!