Three‑Site Routed LAN/WAN — RIP v2

Purpose: Demonstrate end‑to‑end networking fundamentals for recruiters: subnet design, interface addressing, routing (RIP v2), verification, and hardening basics — all implemented in Cisco Packet Tracer.

• Packet Tracer file: rip-routing-configuration.pkt
• Devices: 3x routers (2911/1941-class), 3x 2960 switches, 6x PCs (2 per site)
• WAN: 2 x point‑to‑point serial links using /30 subnets
• LANs: Three /24 networks (left/center/right sites)
• Routing protocol: RIP v2 (classless, multicast updates, no auto summary)
• Goal: Any PC can reach any other PC via dynamic routing; updates are restricted to WAN links (passive on LAN).

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1) Addressing Plan

WAN (Serial point‑to‑point)

Link	Network	Core Side	Edge Side	Mask
Left ↔ Core	10.0.0.0/30	10.0.0.1 (Core Se0/3/0)	10.0.0.2 (Left Se0/3/0)	255.255.255.252
Core ↔ Right	11.0.0.0/30	11.0.0.1 (Core Se0/3/1)	11.0.0.2 (Right Se0/3/0)	255.255.255.252

Why /30? A point‑to‑point link needs only two usable addresses; /30 conserves space and simplifies routes.

LANs

Site	Network	Default Gateway (Router LAN iface)	Example Hosts
Left	192.168.10.0/24	192.168.10.1	192.168.10.10, 192.168.10.11
Center	192.168.20.0/24	192.168.20.1	192.168.20.10, 192.168.20.11
Right	192.168.30.0/24	192.168.30.1	192.168.30.10, 192.168.30.11

Switches may optionally have a management SVI (e.g., 192.168.10.2/24) reachable via the router.

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2) Interface Mapping (topology labels)

• Core router: Se0/3/0 ↔ Left, Se0/3/1 ↔ Right, G0/0 (or F0/0) to the center switch.
• Left router: Se0/3/0 ↔ Core, G0/0 (or F0/0) to left switch.
• Right router: Se0/3/0 ↔ Core, G0/0 (or F0/0) to right switch.

Packet Tracer device models vary; use the LAN‑facing Gigabit/FastEthernet interface on each edge and center router to connect to the access switch.

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3) Router Configurations (Cisco IOS)

Replace interface names if your device uses different slot/port numbering.

3.1 Core Router

hostname CORE
!
interface GigabitEthernet0/0
 ip address 192.168.20.1 255.255.255.0
 no shutdown
!
interface Serial0/3/0
 ip address 10.0.0.1 255.255.255.252
 clock rate 64000    ! Only if this side has the DCE cable
 no shutdown
!
interface Serial0/3/1
 ip address 11.0.0.1 255.255.255.252
 clock rate 64000    ! Only if this side has the DCE cable
 no shutdown
!
router rip
 version 2
 no auto-summary
 passive-interface GigabitEthernet0/0
 network 10.0.0.0
 network 11.0.0.0
 network 192.168.20.0
!
line vty 0 4
 login local
 transport input ssh
!
ip domain-name demo.local
crypto key generate rsa modulus 1024
username admin privilege 15 secret cisco123

3.2 Left Edge Router

hostname EDGE-L
!
interface GigabitEthernet0/0
 ip address 192.168.10.1 255.255.255.0
 no shutdown
!
interface Serial0/3/0
 ip address 10.0.0.2 255.255.255.252
 no shutdown
!
router rip
 version 2
 no auto-summary
 passive-interface GigabitEthernet0/0
 network 10.0.0.0
 network 192.168.10.0

3.3 Right Edge Router

hostname EDGE-R
!
interface GigabitEthernet0/0
 ip address 192.168.30.1 255.255.255.0
 no shutdown
!
interface Serial0/3/0
 ip address 11.0.0.2 255.255.255.252
 no shutdown
!
router rip
 version 2
 no auto-summary
 passive-interface GigabitEthernet0/0
 network 11.0.0.0
 network 192.168.30.0

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4) Switch (2960) Baseline (all three sites)

hostname SW-<SITE>
!
interface range fa0/1-24
 switchport mode access
 spanning-tree portfast
 spanning-tree bpduguard enable
!
! Optional mgmt SVI
interface vlan 1
 ip address 192.168.<10|20|30>.2 255.255.255.0
 no shutdown
!
ip default-gateway 192.168.<10|20|30>.1

If you prefer, create user/data VLANs and trunk them to a router‑on‑a‑stick; for this lab the default access VLAN is sufficient.

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5) End‑Host Settings (per site)

Example (Left PC):

IP:   192.168.10.10
Mask: 255.255.255.0
GW:   192.168.10.1
DNS:  (optional in lab)

Repeat for the center/right sites using their respective subnets and gateways.

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6) Verification & Troubleshooting

On routers:

show ip interface brief
show ip route
show ip rip database
show ip protocols
debug ip rip       ! (lab use only; turn off with 'undebug all')

• Expect R routes for remote LANs (e.g., left sees 192.168.20.0/24 and 192.168.30.0/24 via Serial).
• Ensure no auto-summary is present to avoid classful summarisation issues.

From PCs:

ping 192.168.30.10     # Left PC to Right PC
tracert 192.168.30.10  # Windows traceroute in PT

• If pings fail: check host gateways, interface no shutdown, and that serial links have DCE clock on one side.

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7) Why RIP v2 here? When to use OSPF instead?

• RIP v2 is simple and perfect for demonstrating classless routing, route exchange, and passive interfaces. It supports VLSM and multicast (224.0.0.9).
• OSPF (recommended in production):
  • Faster convergence, loop prevention via SPF.
  • Areas for hierarchy and scale.
  • Rich metrics (cost), authentication, and summarisation.

To migrate: replace router rip with router ospf 1, advertise the three LANs and two /30 links, set passive on LANs, and verify show ip ospf neighbor & show ip route ospf.

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8) Security & Good Practice Highlights

• Passive interfaces on LAN to stop routing updates reaching endpoints.
• SSH for management (transport input ssh, local users, RSA keys).
• PortFast/BPDU Guard on access ports to protect STP.
• Optional ACLs on router LAN interfaces to limit inter‑site traffic.
• Consider NTP for consistent timestamps and Syslog/SNMP for monitoring.

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9) Learning Outcomes (talking points for recruiters)

• Designed VLSM addressing using /30 on WAN and /24 on LANs.
• Implemented dynamic routing (RIP v2), understood advertisements & hop‑count metric.
• Applied passive‑interface and basic switch hardening (STP edge, BPDU Guard).
• Validated reachability with show ip route, ping, and traceroute.
• Can extend to OSPF, DHCP, NAT/PAT, and ACL-based segmentation as next steps.

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10) How to Use

1. Open Cisco Packet Tracer 8.x.
2. Load rip-routing-configuration.pkt.
3. Use the CLI snippets above to re‑configure from scratch or compare with the saved configuration.
4. Test connectivity across sites and observe learned routes.

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Appendix A — OSPF Alternative (optional)

! Core
router ospf 1
 network 10.0.0.0 0.0.0.3 area 0
 network 11.0.0.0 0.0.0.3 area 0
 network 192.168.20.0 0.0.0.255 area 0
 passive-interface g0/0

! Left
router ospf 1
 network 10.0.0.0 0.0.0.3 area 0
 network 192.168.10.0 0.0.0.255 area 0
 passive-interface g0/0

! Right
router ospf 1
 network 11.0.0.0 0.0.0.3 area 0
 network 192.168.30.0 0.0.0.255 area 0
 passive-interface g0/0