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Unit 2: Chapter 8: DHCP (Troubleshooting DHCP (Verify relay agent…

- - - - Router can do DHCPv4 in small enviroment
    - - Lease info admin defined
      - CLient must ask for new address with expires - usually the same
  - - - Broadcast
        
        Layer 2
        
        Layer 3
      - Finds DHCPv4 servers
      - Sent from client
    - - Sent from server
      - Reserves avaliable IPv4 address
      - ARP entry consists of
        
        MAC address of rquesting client
        
        Leased IPv4 address of the client
      - "Offers" address to client
    - - Broadcast
        
        Tells other DHCPv4 servers that their offer has not been used
      - Lease origination
        
        Serves are binding acceptance notice for select server
        
        Server as implicit deny for other servers #
      - Lease renewal
    - - Server verifies lease information not already used
        
        ICMP ping
      - ARP message
        
        Client MAC address
        
        New IP address
      - Exactly the same as DHCPOFFER except for different mssage type field
      - When client receives
        
        Logs configuration information
        
        Peforms ARP
        
        makes sure there is no other client
        
        If no reply sets addresing information
  - - - Sent by client before lease expires
      - Sent directly to DHCPv4 server
      - If no response; DHCPRQUEST sent to another server
- - - - 4 steps
        
        RA
        
        "Here a Prefix, prefix length.
        
        IPv6 Globl Unicast Address
        
        genetates interface ID then uses the Prefix length and prefx to create IPV6 Address
        
        EUI-64
        
        Create IID with 48-bit MAC ddress
        
        Randomly generated
        
        the 64 bit IID can be a randomly generate number from the OS
        
        RS
        
        "I need an RA from the router
        
        Duplicate Address detection
        
        duplicates the last 24-Bits of the address (solicited-node multicast address)
        
        if no devices respond with NA message then the address is not in use
        
        Part of ICMP v6 neighbor discovery called DAD
        
        "is the address ready to use"
      - Ipv6 unicast routing command before use
    - - decsion on configuration of ipv6 addres depends on two flags
        
        Other Configuration Flag (O Flag)
        
        O flag not M Flag is Statless
        
        No Flags set is SLAAC
        
        Regardless of what flags are set they all use DAD
        
        Managed Address configuaton Flag (M Flag)
        
        M Flag not O flag is Stateful
    - - dynamic assginment of IPV6 Addresses
        
        Stateful DHCP
        
        full Server
        
        SLAAC
        
        No server, Stateless
        
        Uses RS and RA messages
        
        RA
        
        FF02::1
        
        sent routers to provide addressig to clients
        
        RS
        
        Sent by client to router
        
        FF02::2
    - - Default Option
      - Uses infomation in the RA message exlucisilvely
        
        Prefix-Length
        
        DNS Server
        
        Prefix
        
        MTU
        
        Default gateway
      - resetting flags
        
        no ipv6 nd other-config-flag
        
        no ipv6 nd managed-config-flag
    - - uses the infomation in the RA for addressing but addtional infomation is gained from the server
        
        server gives
        
        IPv addresses
        
        lists of DNS Server
      - Command to set the interface to stateless
        
        ipv6 nd other-config-flag
    - - All addressing and configuration infomation is gained rom the Server
      - Command to se statful on the Interface
        
        ipv6 nd managed-config-flag
      - Mos simliar to DHCpv4
    - - DHCv6 client locating server
        
        DHCPv6 REQUEST or INFORMATION-REQUEST
        
        depends if its stateful or stateless
        
        DHCPv6 REPLY unicast message
        
        cotains infomation requested
        
        DHCPv6 ADVERTISE unicast message
        
        informs DHCpv6 clent that the server is available
        
        DHCPv6 SOLICIT message
        
        FF02::1:2 (link scope routers do not forward)
      - DHCPv6 messges are sent over UDP
        
        Client to server destinaton port 547
        
        Server to client destination port 546
- - - - Broadcast address of 255.255.255.255
    - - CIADDER: CLient IP address
      - GIADDR: CLient default gateway address
      - CHADDER: Client Hardware Address (Usually sorce MAC address)
- - - - Put router in DHCPv4 config mode
  - - - Define pool address
    - - Define default gateway IP address
    - - Define DNS server (single address)
    - - Define domain name
    - - Change default lease time
  - - - Disable DHCPv4
    - - Enable DHCPv4
  - - - Verify messages are being received or sent
- - - - Port 37: Time
        
        Port 49: TACACS
        
        Port 53: DNS
        
        Port 67: DHCP/BOOTP client
        
        Port 68: DHCP/BOOTP server
        
        Port 69: TFTP
        
        Port 137: NetBIOS name service
        
        Port 138: NetBIOS datagram service
- - - - Uses ARP
  - - - debug ip packet access-list
        
        An list defining ports 67 and 68 would have to be defined - an EXTEDNED ACL
    - - debug ip dhcp server events