Lec 4
It looks like you have some questions related to DHCP, subnetting, and other networking concepts. I'll help clarify each one and explain where you might have gone wrong.
### Question 1: Centralising DHCP Servers
Correct Answer: Configure DHCP relay agents in each building to forward DHCP packets to the DHCP servers in the ITS building.
Explanation: When you centralise DHCP servers, clients in different buildings won’t be able to communicate directly with the DHCP server without a DHCP relay agent. The 169.254.0.0/16 addresses indicate that the clients are using Automatic Private IP Addressing (APIPA) because they couldn't reach a DHCP server. Configuring DHCP relay agents will forward the DHCP requests from different subnets to the central DHCP server.
### Question 2: Subnetting
Correct Answer: 30.
Explanation: You borrowed 3 bits, so the new subnet mask is /27. This leaves 5 bits for host addresses, which allows for \(2^5 - 2 = 30\) usable host addresses per subnet.
### Question 3: DHCP Server Authorisation
Correct Answer: Kim forgot to authorise the new DHCP server.
Explanation: In a Windows Active Directory environment, DHCP servers must be authorised in AD to lease IP addresses. If this step is missed, the server will not function correctly, leading to clients not receiving IP addresses.
### Question 4: Finding a DHCP Server
Correct Answer: The PC sends out a broadcast in order to discover which DHCP servers are available.
Explanation: A client PC that is set to obtain an IP address automatically will send out a DHCPDISCOVER broadcast on the network to find available DHCP servers.
### Question 5: Supernetting
Correct Answer: 192.168.2.64/28 & 192.168.2.80/28.
Explanation: Supernetting combines smaller networks into a larger one, but the selected subnet pairs need to be contiguous and the network boundary must align. The pair 192.168.2.64/28 & 192.168.2.80/28 cannot be supernetted because they are not contiguous.
### Question 6: Network Subnetting
Correct Answer: Variable Length Subnet Masks (VLSM).
Explanation: VLSM allows for subnets of different sizes within the same network, enabling more efficient use of IP addresses by applying different subnet masks at different levels.
### Question 7: Creating Subnets
Correct Answer: 4.
Explanation: To create 14 subnets, you need to borrow enough bits to accommodate at least 14 subnets. \(2^4 = 16\), which is the smallest number that can cover 14, so 4 bits are required.
### Question 8: DHCP Options
Correct Answer: 10.0.0.3.
Explanation: DHCP options are applied in the following order of precedence: Reservation > Scope > Server > Class. Since a reservation was made for the PC with a gateway of 10.0.0.3, that would be the address assigned after the renewal.
### Question 9: Matching DHCP Option Codes
Correct Answer:
- 003: Router
- 006: DNS Servers
- 015: DNS domain name
- 007: Not a DHCP option, an MI6 spy
### Question 10: DHCP Renewal
Correct Answers:
- A PC will first attempt to renew its IP address when 50% of the lease time has expired.
- If the first attempt to renew an IP address fails, a PC will have a second attempt when 87.5% of the lease time has expired.
- If the PC has not successfully renewed its IP address, when 100% of the lease time has expired it will send a DHCPdiscover broadcast.
Explanation: The DHCP renewal process has specific timings, with the first renewal attempt at 50%, a second at 87.5%, and if both fail, the client will attempt a DHCPDISCOVER at 100% of the lease time.
### Question 11: DHCP Packet Order
Correct Order:
1. DHCPDISCOVER
2. DHCPOFFER
3. DHCPREQUEST
4. DHCPACK
### Question 12: DHCP Negotiation
Correct Answers:
- As a unicast, a DHCPoffer packet
- As a unicast, a DHCPack packet
- As a broadcast, a DHCPdiscover packet
Explanation: The DHCP server sends DHCPOFFER and DHCPACK as unicast packets to the requesting client. DHCPDISCOVER is broadcast by the client to discover available DHCP servers.
Hopefully, these explanations help clear up your misunderstandings! If you have more questions or need further clarification, feel free to ask.