--- title: "Redundant hierarchical network design for bank" subject: "Internet and Intranet" chapter: 5 key: "semester_8/internet_and_intranet:redundant-network-bank-four-departments" source: https://www.bctengineer.com/q/semester_8/internet_and_intranet/redundant-network-bank-four-departments site: BCT Engineering --- # Redundant hierarchical network design for bank Internet and Intranet · Chapter 5: Designing Internet Systems and Servers - Asked in: 2072 Magh, 12 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/internet_and_intranet/redundant-network-bank-four-departments - Whole chapter: https://www.bctengineer.com/md/semester_8/internet_and_intranet/chapter-5 ## Question 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. ## 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. ## Answer #### 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 ```text 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. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which set lists factors for a well-designed network according to the answer? A. Performance, reliability, scalability, security, manageability, cost B. Colour, brand, weight, size C. Only speed and price D. Cable length, rack height, wall colour Answer: A. Key factors include performance, reliability/availability, scalability, security, manageability, cost, flexibility and QoS. (Key point: Design factors) 2. How does the design keep the default gateway available if one core switch fails? A. Two L3 core switches run VRRP and are joined by LACP B. A single large switch with a spare cable C. Each PC uses a static route to the internet D. The firewall acts as the only gateway Answer: A. VRRP shares a virtual gateway between the two core switches, so the gateway survives a failure. (Key point: Core redundancy) 3. How is each access switch connected to avoid loops while staying redundant? A. One uplink only, to a single core B. Two uplinks, one to each core, bundled as a port-channel, with RSTP as backup C. Daisy-chained to the next access switch D. Connected to the firewall directly Answer: B. Dual uplinks bundled into one port-channel give redundancy without a loop; RSTP is a backup protection. (Key point: Access uplinks) 4. Why does Finance get a /26 while HR gets a /27? A. Finance has 45 PCs plus DHCP and AP, which exceeds the 30 hosts of a /27 B. Finance needs fewer addresses C. A /26 is used for every department D. HR has more servers Answer: A. A /27 gives 30 usable hosts, enough for HR's 20 PCs and extras, but Finance with 45 PCs needs the 62 hosts of a /26. (Key point: Subnet sizing) 5. Where do the IT servers that are visible from the internet sit? A. In every department VLAN B. In a DMZ behind the firewall C. Outside the firewall with no protection D. On the management VLAN Answer: B. The firewall protects the internal network while internet-facing servers are placed in a DMZ. 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