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Configure Secure WAN Link and Network Redundancy

Summary​

Configured a secure WAN connection using PPP with CHAP authentication between ProvoRouter and ISP2, then implemented OSPF to provide a redundant path to the internet. Tested failover by shutting down the primary ISP link and verified continued connectivity via the secondary path.

From a gospel perspective, this reflects the principle of preparation and resilience. In Matthew 7:24–25, Christ teaches that building on a strong foundation helps withstand storms. Similarly, network redundancy ensures that systems remain functional even when part of the network fails.

Notes​

Initial Verification​

Accessed the ProvoRouter CLI and verified interfaces:

show ip int br

No serial interfaces were present, confirming that additional hardware was needed.

Adding the Serial Module​

Went to the Physical tab, powered off the router, installed the HWIC-2T module, and powered it back on. Verified that serial interfaces (s0/2/0 and s0/2/1) appeared after restart.

Interface Configuration​

conf t
int s0/2/0
ip address 198.3.26.1 255.255.255.252
no shutdown

Cable Connection​

Used a Serial DCE cable and connected:

  • ISP2 s0/0/0 (DCE)
  • ProvoRouter s0/2/0 (DTE)

PPP and CHAP Configuration​

Initial ping failed due to encapsulation mismatch. Fixed with:

conf t
int s0/2/0
encapsulation ppp
ppp authentication chap

Added authentication credentials:

username ISP2 password cisco

After waiting for negotiation, the link came up and a ping to 198.3.26.2 succeeded.

Part 2: Configuring OSPF for Redundancy​

Advertised the new WAN link via OSPF:

conf t
router ospf 4
network 198.3.26.0 0.0.0.3 area 0

Verification​

On TrainRouter:

show ip route

Confirmed 198.3.26.0/30 appeared in the routing table, verifying OSPF propagation.

Part 3: Testing Network Redundancy​

Before Failure​

On PC2, confirmed normal routing:

tracert www.cisco.com

Showed the expected route through the primary ISP.

Simulating Failure​

On the SLC DHCP Router:

conf t
int gi0/0/0
shutdown

After Failure​

Back on PC2:

  • Verified www.cisco.com still resolved and loaded
  • Ran tracert again and observed a different route

Traffic had failed over to the new WAN link automatically.

Results​

  • PPP with CHAP authentication successfully configured
  • OSPF advertised the new WAN network correctly
  • Internet connectivity remained after primary link failure
  • Traceroute confirmed failover behavior

Insights​

This lab demonstrated how redundancy and secure authentication work together to improve reliability. Without a secondary path, a single link failure takes down the entire network. By adding a secondary WAN and dynamic routing with OSPF, the network adapts automatically — no manual intervention required.

The CHAP authentication piece was a useful reminder that WAN links need to be secured just like LAN access. PPP encapsulation with CHAP ensures both sides authenticate before traffic flows.

From a gospel perspective, this connects to the principle in Ether 12:27 — that weaknesses can become strengths through preparation and effort. Designing networks with redundancy turns potential failure points into strengths. The same principle applies in life: building backup plans and resilient habits prepares us to weather disruptions without being taken down by them.

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