Which set lists factors for a well-designed network according to the answer?

Performance, reliability, scalability, security, manageability, cost

Cable length, rack height, wall colour

How does the design keep the default gateway available if one core switch fails?

Two L3 core switches run VRRP and are joined by LACP

A single large switch with a spare cable

Each PC uses a static route to the internet

The firewall acts as the only gateway

How is each access switch connected to avoid loops while staying redundant?

Two uplinks, one to each core, bundled as a port-channel, with RSTP as backup

One uplink only, to a single core

Daisy-chained to the next access switch

Connected to the firewall directly

Why does Finance get a /26 while HR gets a /27?

Finance has 45 PCs plus DHCP and AP, which exceeds the 30 hosts of a /27

A /26 is used for every department

Where do the IT servers that are visible from the internet sit?

Outside the firewall with no protection

2072 Magh · 12 marks

Redundant hierarchical network design for bank

Short answer

Factors include performance, reliability through redundancy, scalability, security, manageability, cost, flexibility, and QoS. The hierarchical design uses dual edge routers and firewalls in HA for internet, two L3 core switches with VRRP and LACP for redundancy, and separate L2 access switches per department (two for Finance). VLANs, a DMZ, and dual NIC server connections are employed.

What are the factors to be considered for a well designed network? Considering these factors, propose a redundant network design architecture in hierarchical form for a bank having four departments namely Human Resources (20 PCs), Marketing (20 PCs), Finance (45 PCs) and IT (30PCs). Each department has managed own DHCP server. IT department has managed FTP server, HTTP server and DNS server as well. Use suitable L1, L2 and L3 devices, physical wires, patch cords, patch panels and wireless access points.

Factors for a well-designed network

Factor	Meaning
Performance	Enough bandwidth, low delay and low oversubscription
Reliability / availability	Redundant paths and devices, UPS, fast recovery
Scalability	Easy to add users, floors and services
Security	Firewall, VLANs, ACLs, authentication, encryption
Manageability	Monitoring, standard devices, documentation
Cost	Good value over the whole life
Flexibility / standards	Open standards, modular design
Quality of service	Priority for voice and critical traffic

Assumptions

The departments are in one building with 4 floors: HR (20 PCs), Marketing (20), Finance (45), IT (30). Each department has its own DHCP server (4 DHCP servers).
IT also manages the FTP, HTTP and DNS servers (3 servers). One AP and one printer per department.
Average horizontal cable length 35 m.

Hierarchical redundant design

      ISP-1                ISP-2
        |                    |
   [Edge Router-1]    [Edge Router-2]
        |       \      /     |
   [Firewall-1]==HA==[Firewall-2] --- DMZ (HTTP/FTP/DNS)
        |       /      \     |
    [Core-1]===LACP===[Core-2]    Core + distribution
     |  \        /   |             (L3, VRRP gateways)
     |   \      /    |
  +--+----+----+-----+--+
  |       |         |   |
[SW-HR][SW-MK][SW-FIN a/b][SW-IT]  Access (L2)
 20PC   20PC   45PC       30PC
 DHCP   DHCP   DHCP       DHCP
 AP     AP     AP         AP

Edge: two routers, each on a different ISP, and two firewalls in an active/standby HA pair, so neither the internet link, the router nor the firewall is a single point of failure.
Core/distribution layer: two L3 switches, joined by an LACP peer link and working as one logical pair (stack/MLAG). They route between VLANs and run VRRP so the default gateway survives the failure of one core.
Access layer: one L2 switch per department (two for Finance). Every access switch has two uplinks, one to each core switch, bundled as one port-channel, so there is no loop. RSTP runs as a backup.
Servers: dual NICs (teamed) connected to two switch ports.
The firewalls protect the internal network; the IT-managed servers that must be reached from the internet (HTTP, FTP, public DNS) sit in a DMZ.

Devices and wires

Layer	Device	Qty
L1	CAT6 UTP cable (123 drops x 35 m x 1.1 = 4,740 m)	16 boxes
L1	Fibre/CAT6 uplinks core-to-access (5 switches x 2)	10
L1	Patch panels 24-port (123 drops)	6
L1	Patch cords 2 m / 1 m	123 / 123
L1	Faceplates	123
L2	24-port PoE switch (HR, Marketing)	2
L2	48-port PoE switch (Finance, IT)	2
L2	24-port switch (Finance extra, printers)	1
L3	L3 core switch, 24-port + SFP+	2
L3	Edge router; firewall (HA pairs)	2; 2
Other	Wireless AP	4
Other	DHCP servers (one per dept); FTP, HTTP, DNS servers	4; 3

The 123 drops are 115 PCs + 4 APs + 4 printers. The 7 servers are patched directly to switch ports in the server room.

IP plan (172.16.0.0/16)

Department	Hosts needed	Subnet	Usable	Gateway
HR	20 PCs + DHCP + AP + printer	172.16.10.0/27	30	.1
Marketing	20 PCs + DHCP + AP + printer	172.16.20.0/27	30	.1
Finance	45 PCs + DHCP + AP + printer	172.16.30.0/26	62	.1
IT	30 PCs + DHCP + AP + printer	172.16.40.0/26	62	.1
DMZ	HTTP, FTP, DNS servers	172.16.50.0/28	14	.1
Management		172.16.99.0/27	30	.1

The .1 gateway in each VLAN is the VRRP virtual address shared by the two core switches. Each department's DHCP server is in its own VLAN, so no relay is needed. Each server has its own scope (for example .2 - .25 in HR for PCs and the AP), and static addresses at the top of the range (.26 - .30 in HR) are kept for the DHCP server and the printer.

✓ Answer checked by Claude Opus 5.5 (high effort)

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