DHCP

• dynamic host config protocol

  

  

  • lease time decided by server

  DHCP IP ALLOCATION

  • message types

    • DISCOVER
      • transport layer, udp broadcast
      • to find dhcp servers in that n/w
      • port UDP 67
    • OFFER
      • unicast to requested device, saying i cant offer you an ip
      • port UDP 68
    • REQUEST
      • broadcast - yes, not unicast, eventhough device knows dhcp address it will intentionally sends broadcast..
        • TO ENSURE OTHERS DHCP SERVERS IN N/W KNOW, THAT IP Assigned to that device is marked as BLOCKED + who given that ip to that device
    • ACK
      • unicast to device with requested IP
      • now device can use it

    

    DHCP Lease

    

    • additional settings like DNS server ip, etc..

    

  • Address pool may be

    1. start to end range
    2. start to max no.of hosts
    3. set of allowed ips along with mask

  

• starvation attack is kinda spamming the real dhcp server by sending huge no.of dhcp requests using fake MACs