# BGP & OSPF Multi-Area Routing Lab: ISP Peering & Route Redistribution ## Introduction This lab simulates an **enterprise network peering with two ISP routers via BGP**, while utilizing a **multi-layered, multi-area OSPF topology** for internal routing. The goal of this setup is to explore **BGP peering, OSPF multi-area configuration, route redistribution, VLAN segmentation, DHCP services, and external DNS integration**. This is part of my **Bits of Progress** journey, where I document my hands-on networking experience. Rather than a step-by-step tutorial, this blog post presents my thought process, configurations, and the learning experience gained from building this lab. --- ## **Lab Topology Overview** ### **Key Components:** 1. **ISP Routers (BGP AS 65010 & 65020)** – Simulate two separate ISPs peering with the enterprise network. 2. **Core Routers (BGP AS 65001, OSPF Backbone Area 0)** – Serve as the backbone of the enterprise, interconnecting various OSPF areas and managing route redistribution. 3. **Access Routers (OSPF Area 1, DHCP Services)** – Provide connectivity to end devices in separate VLANs. 4. **Access Switches (Layer 2 VLAN Segmentation)** – Facilitate communication between clients, servers, and IoT devices. 5. **ISP Exchange Router (BGP AS 65050)** – Acts as an intermediary router simulating upstream internet access. --- ## **Configuration Breakdown** ### **1\. BGP Peering & Route Redistribution** The **core routers** establish BGP sessions with the ISP routers while also redistributing internal OSPF routes into BGP. #### **CoreRouter1 BGP Configuration:** ```plaintext router bgp 65001 bgp log-neighbor-changes aggregate-address 192.168.0.0 255.255.0.0 summary-only aggregate-address 10.0.0.0 255.0.0.0 summary-only redistribute ospf 1 match internal external 1 external 2 neighbor 172.16.2.1 remote-as 65010 ``` * **Redistributes OSPF routes into BGP**, allowing the enterprise network to advertise summarized internal networks to the ISPs. * **Uses aggregate addressing** to reduce the number of advertised routes. #### **ISPRouter1 & ISPRouter2 BGP Configuration:** ```plaintext router bgp 65010 bgp log-neighbor-changes network 172.16.1.0 mask 255.255.255.252 network 172.16.2.0 mask 255.255.255.252 neighbor 172.16.1.2 remote-as 65020 neighbor 172.16.2.2 remote-as 65001 neighbor 172.16.2.2 route-map ADVERTISE-DEFAULT-ROUTE out neighbor 172.16.4.1 remote-as 65050 ``` ```plaintext router bgp 65020 bgp log-neighbor-changes network 172.16.3.0 mask 255.255.255.252 network 172.16.5.0 mask 255.255.255.252 neighbor 172.16.1.1 remote-as 65010 neighbor 172.16.3.2 remote-as 65001 neighbor 172.16.3.2 route-map ADVERTISE-DEFAULT-ONLY out neighbor 172.16.5.1 remote-as 65050 ``` * Both ISPs advertise a **default route** to the enterprise network. * **ISPRouter2 (AS 65020) also peers with ISPRouter1 (AS 65010)**, forming a redundant external connection. --- ### **2\. OSPF Multi-Area Design** The enterprise network follows a structured OSPF design with multiple areas for efficient routing and scalability. #### **CoreRouter1 OSPF Configuration:** ```plaintext router ospf 1 router-id 1.1.1.1 network 10.1.0.0 0.0.0.3 area 0 network 10.1.1.0 0.0.0.3 area 0 network 10.1.2.0 0.0.0.3 area 0 default-information originate metric-type 1 ``` * **OSPF Backbone (Area 0)** connects all access routers. * Advertises the default route to propagate **internet access throughout the network**. #### **AccessRouter1 OSPF Configuration:** ```plaintext router ospf 1 router-id 2.2.1.1 network 192.168.10.0 0.0.0.255 area 1 network 192.168.20.0 0.0.0.255 area 1 network 192.168.30.0 0.0.0.255 area 1 ``` * Belongs to **Area 1** and connects local VLANs to the enterprise network. * Establishes an **OSPF adjacency with CoreRouter1**. --- ### **3\. VLANs, Subnets, and DHCP** Each **Access Router** provides DHCP services for clients, servers, and IoT devices. #### **AccessRouter1 DHCP Configuration:** ```plaintext ip dhcp pool CLIENTS1 network 192.168.10.0 255.255.255.0 default-router 192.168.10.1 dns-server 8.8.8.8 ``` * Assigns IPs dynamically to devices in VLAN 10 (Clients). * Uses **Google’s DNS (8.8.8.8)** for external name resolution. --- ## **Testing & Validation** ### **1\. BGP Neighbor Verification** Checking BGP peers from **CoreRouter1**: ```plaintext CoreRouter1# show ip bgp summary ``` * Ensures BGP sessions are **established with ISP routers**. ### **2\. OSPF Neighbor Verification** Checking OSPF neighbors on **AccessRouter1**: ```plaintext AccessRouter1# show ip ospf neighbor ``` * Confirms **OSPF adjacencies with CoreRouter1**. ### **3\. Route Summarization Check** Checking advertised routes on **ISP Routers**: ```plaintext ISPRouter1# show ip bgp ``` * Confirms that **only summarized routes are advertised** to the ISPs. --- ## **Conclusion** This lab was a great learning experience in **BGP peering, OSPF multi-area routing, and network services like VLANs and DHCP**. By configuring an ISP environment and enterprise network, I gained hands-on insight into real-world networking scenarios. This is just one step in my **Bits of Progress** journey. Stay tuned for more labs and technical deep dives. --- 📺 **Watch the Lab in Action:** [https://youtu.be/cb68HlbxOk8](https://youtu.be/cb68HlbxOk8) 📂 **Download Config Files:** [https://github.com/PRivers251/RoutingLab\_BGP\_OSPF\_3-6-25](https://github.com/PRivers251/RoutingLab_BGP_OSPF_3-6-25)