CCNP Route - 300-101 - Sub-Topics - DHCPv6 + Stateless Autoconfig

LynK · February 02, 2017, 02:00:14 PM

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DHCPv6

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There are two types of DHCPv6:

- Stateful
- Stateless

Stateful DHCPv6 – Address assignment is centrally managed, and that clients must obtain configuration information from address autoconfiguration and neighbor discovery.
Stateless DHCPv6 – Does not require a server to maintain any state/client information. This includes things such as DNS, domain searching.

Stateful DHCPv6 works almost identically to traditional DHCP. Host A sends a multicast looking for a DHCP server (SOLICIT MESSAGE). DHCP server REPLIES, then the client asks for an IP address. The server REPLIES giving a bunch of information:
-IPv6 address
-Prefix length
-DNS IP addresses

Multicast Address used by CLIENTS to find UNKNOWN DHCP SERVERS: FF02::1:2

*One of the things Stateful DHCP leaves out is the DEFAULT ROUTER INFORMATION. That is because it is relying on NDP (IPv6 ARP essentially) for that information.

Here are some KEY message types you need to know:
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SOLICIT - A DHCPv6 client sends a Solicit message to locate DHCPv6 servers.
ADVERTISE - A server sends an Advertise message to indicate that it is available for DHCP service, in response to a Solicit message received from a client.
REQUEST - A client sends a Request message to request configuration parameters, including IP addresses or delegated prefixes, from a specific server.
CONFIRM - A client sends a Confirm message to any available server to determine whether the addresses it was assigned are still appropriate to the link to which the client is connected.
RENEW - A client sends a Renew message to the server that originally provided the client's addresses and configuration parameters to extend the lifetimes on the addresses assigned to the client and to update other configuration parameters.
REPLY - A server sends a Reply message containing assigned addresses and configuration parameters in response to a Solicit, Request, Renew, Rebind message received from a client.
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To configure Stateful DHCPv6:

Code Select


!####################SERVER CONFIG####################!
!
ipv6 unciast-routing
!
ipv6 dhcp pool CCNP_IPV6_DHCP
   address prefix 2001:1111:9999:FFFF::/64 lifetime 21600 21600
   dns-server 2999:AAAA:BBBB::1
   domain-name networking-forums.com
!
interface gi0/0
 ipv6 address 2001:1111:9999:FFFF::1/64
 ipv6 nd prefix 2001:1111:9999:FFFF::/64 21600 21600 no-autoconfig
 ipv6 nd managed-config-flag
 ipv6 dhcp server CCNP_IPV6_DHCP

!####################CLIENT CONFIG####################!
!
ipv6 unicast-routing
!
interface gi0/0
   ipv6 address dhcp
   ipv6 enable

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Stateless Autoconfiguration

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Stateless DHCPv6 performs one action: it supplies the DNS server's IPv6 addresses to clients. Stateless DHCP goes hand in hand with stateless autoconfiguration, so lets talk about that!

Stateless Autoconfiguration

This is where it gets COOL (especially if you are into vulnerabilities). Stateless autoconfiguration permits a HOST to AUTOMATICALLY LEARN THE KEY PIECES OF ADDRESSING INFORMATION such as:
-Prefix
-Prefix Mask
-Host
-Prefix Length

Do you know how it learns all this information? Through its upgraded ARP (NDP). Host X needs to figure out his own address, he does this by using the EUI-64 format. Once he has a Link Local address this is how it works:

1) HOST X sends a Router Solicitation message to all routers (FF02::2) saying:
-TELL ME WHO YOU ARE. SPECIFICALLY TELL ME YOUR IPv6 ADDRESSES
-TELL ME YOUR PREFIXES
2) ROUTER-A responds with a Router Advertisement to all nodes (FF02::1), saying:
-MY PREFIX IS: 2300:1212:AAAA:1::/64
-MY DEFAULT ID IS: 2300:1212:AAAA:1:444:19FF:FE99:0945

To configure stateless-autoconfiguration:

Code Select


!####################SERVER CONFIG####################!

ipv6 dhcp pool CCNP_IPV6_STATELESS_DHCP
   dns-server 2999:AAAA:BBBB::1
   domain-name networking-forums.com
!
interface Gi0/0
   ipv6 address 2001:1111:9999:FFFF::1/64
   ipv6 dhcp server CCNP_IPV6_STATELESS_DHCP
   ipv6 nd other-config-flag

!####################CLIENT CONFIG####################!

interface Gi0/0
ipv6 address autoconfig default

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PRACTICE QUESTIONS:

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1) What two types of DHCP are there for IPv6?
2) Which type of DHCPv6 is most like traditional DHCP?
3) What two types of messages used between a client and a stateful DHCPv6 server?
4) What is the multicast address clients use to find unknown DHCPv6 servers?
5) True or False: A Stateless DHCP tracks client information such as prefix/length and DNS?
6) What is the purpose of a stateless DHCP server?
7) What two types of messages does stateless autoconfiguration use?
8.) If an interface is configured with "ipv6 address autoconfig" what type of DHCP is it using?
9) What is the EUI Format if my ipv6 prefix is: 2001:9999:1234:1::/64 and the MAC is: 0012.711b.1234?
10) Put the four DHCP messages in order: ADVERTISE, SOLICIT, REPLY, REQUEST. Then explain the process.
11) How many Messages are in the stateless DHCP communication with the client? Then explain the process

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PRACTICE ANSWERS:

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[spoiler]
1) A: Stateful & Stateless
2) A: Stateful DHCPv6
3) A: SOLICIT & REPLY
4) A: FF02::1:2
5) A: FALSE
6) A: To provide DNS IPs to clients
7) A: Router Soliciation & Router Advertisement
8.) A: Stateless autoconfiguration
9) A: 2001:9999:1234:1:0012:71FF:FE1b:1234
10) A: SOLICIT, ADVERTISE, REQUEST, REPLY
A: The client SOLICITs for any available servers, the server responds with an ADVERTISE message. The client sends a REQUEST message to confirm the information in the advertise message. Then the server REPLYs with the confirmed information.
11) A: 2 (SOLICIT & REPLY)
A: Client sents solicit asking for DNS, server reply's with DNS.
[/spoiler]

CCNP Route - 300-101 - Sub-Topics - DHCPv6 + Stateless Autoconfig

LynK