🎯 Welcome to the Advanced BGP Lab
This comprehensive lab will take you through advanced BGP concepts and real-world configurations used in enterprise and service provider networks.
🎓 What You'll Learn
- Route Reflectors: Configure BGP route reflectors to scale iBGP without full mesh requirements
- BGP Confederations: Implement confederations to divide large AS into smaller sub-autonomous systems
- BGP Communities: Use standard and extended communities for traffic engineering and route manipulation
- Advanced Path Selection: Master BGP attributes including LOCAL_PREF, AS_PATH prepending, and MED
- Route Filtering: Apply prefix-lists, route-maps, and AS-path filters effectively
- BGP Best Path Algorithm: Understand the complete BGP decision process
- Traffic Engineering: Implement inbound and outbound traffic control techniques
🏢 Lab Environment
This lab simulates an enterprise network with multiple sites connected to two ISPs. You'll configure:
- 4 Internal routers forming an iBGP mesh with route reflectors
- 2 ISP connections with diverse paths
- Traffic steering using BGP communities
- Redundancy and failover scenarios
💡 Why This Matters
BGP is the routing protocol of the Internet. Understanding advanced BGP concepts is crucial for network architects, engineers managing multi-homed networks, and anyone working in service provider environments. These techniques are used daily to optimize traffic flow, ensure redundancy, and implement complex routing policies across thousands of production networks worldwide.
✨ Ready to Begin?
Click through the tabs above to progress through the lab. Start with the Topology to understand the network layout, then move to Prerequisites before diving into Configuration.
Click through the tabs above to progress through the lab. Start with the Topology to understand the network layout, then move to Prerequisites before diving into Configuration.
🗺️ Network Topology
Our lab network consists of an enterprise network (AS 65100) connected to two ISPs (AS 65200 and AS 65300).
Internet
|
+---------------+---------------+
| |
ISP-A (AS 65200) ISP-B (AS 65300)
192.168.1.1 192.168.2.1
| |
| .2 .2 |
| |
[R1]---------------------------- [R2]
(RR-Client) 10.0.12.0/30 (RR-Client)
.1 | \ / | .2
| \ / |
| \ 10.0.13.0/30 / |
| \ / |
| \ / |
| \ / |
| \ [R3] / |
| \ (RR) / |
| \ .3 / |
| 10.0.14.0/30 \ / 10.0.23.0/30
| \ / |
| X |
| / \ |
| / \ |
| / \ |
| .4/ \.4 |
| / \ |
| / \ |
| / \ |
| [R4]---------------+ |
| (RR-Client) 10.0.24.0/30 |
| .4 |
| |
LAN-A LAN-B
172.16.1.0/24 172.16.2.0/24
Enterprise AS: 65100
ISP-A AS: 65200
ISP-B AS: 65300
Route Reflector: R3
Route Reflector Clients: R1, R2, R4
📊 Network Details
| Router | Role | AS Number | Loopback |
|---|---|---|---|
| R1 | Edge Router / RR Client | 65100 | 1.1.1.1/32 |
| R2 | Edge Router / RR Client | 65100 | 2.2.2.2/32 |
| R3 | Route Reflector | 65100 | 3.3.3.3/32 |
| R4 | Internal Router / RR Client | 65100 | 4.4.4.4/32 |
📋 Prerequisites
🔧 Required Knowledge
- Strong understanding of BGP fundamentals (eBGP and iBGP)
- Familiarity with BGP attributes (AS_PATH, LOCAL_PREF, MED, NEXT_HOP)
- Experience with router CLI (Cisco IOS or similar)
- Understanding of IP routing and subnetting
- Knowledge of route-maps and prefix-lists
1
Verify Physical Connectivity
# Verify interface status
show ip interface brief
# Test connectivity to neighbors
ping 10.0.12.2
ping 10.0.13.3
✅ Pre-Configuration Checklist:
☐ All interfaces operational
☐ IGP (OSPF) converged
☐ Loopback addresses reachable
☐ All interfaces operational
☐ IGP (OSPF) converged
☐ Loopback addresses reachable
⚙️ Configuration Steps
1
Configure R1 - Edge Router
router bgp 65100
bgp router-id 1.1.1.1
neighbor 192.168.1.1 remote-as 65200
neighbor 192.168.1.1 description ISP-A
neighbor 3.3.3.3 remote-as 65100
neighbor 3.3.3.3 update-source Loopback0
neighbor 3.3.3.3 next-hop-self
network 1.1.1.1 mask 255.255.255.255
💡 Key Concept: next-hop-self
The next-hop-self command is critical for iBGP. It changes the next-hop to R1's IP so internal routers can reach external destinations.
2
Configure R2 - Edge Router
router bgp 65100
bgp router-id 2.2.2.2
neighbor 192.168.2.1 remote-as 65300
neighbor 192.168.2.1 description ISP-B
neighbor 3.3.3.3 remote-as 65100
neighbor 3.3.3.3 update-source Loopback0
neighbor 3.3.3.3 next-hop-self
network 2.2.2.2 mask 255.255.255.255
3
Configure R3 - Route Reflector
router bgp 65100
bgp router-id 3.3.3.3
bgp cluster-id 3.3.3.3
neighbor 1.1.1.1 remote-as 65100
neighbor 1.1.1.1 update-source Loopback0
neighbor 1.1.1.1 route-reflector-client
neighbor 2.2.2.2 remote-as 65100
neighbor 2.2.2.2 update-source Loopback0
neighbor 2.2.2.2 route-reflector-client
neighbor 4.4.4.4 remote-as 65100
neighbor 4.4.4.4 update-source Loopback0
neighbor 4.4.4.4 route-reflector-client
network 3.3.3.3 mask 255.255.255.255
💡 Route Reflector Magic
R3 reflects routes between clients, eliminating the need for full-mesh iBGP. With 4 routers, this reduces sessions from 6 to 3!
4
Configure R4 - Internal Router
router bgp 65100
bgp router-id 4.4.4.4
neighbor 3.3.3.3 remote-as 65100
neighbor 3.3.3.3 update-source Loopback0
network 4.4.4.4 mask 255.255.255.255
🔧 Troubleshooting Guide
1
BGP Neighbor Won't Establish
show ip bgp summary
show ip bgp neighbors 3.3.3.3
ping 3.3.3.3 source loopback0
⚠️ Common Causes:
• Wrong AS number in remote-as command
• No IP reachability (check IGP)
• Update-source mismatch
• Firewall blocking TCP 179
• Wrong AS number in remote-as command
• No IP reachability (check IGP)
• Update-source mismatch
• Firewall blocking TCP 179
2
Routes Not Being Advertised
💡 iBGP Split Horizon Rule
Routes learned via iBGP are NOT advertised to other iBGP peers. This is why route reflectors are essential!
✅ Verification Procedures
🔍 Step 1: Verify BGP Neighbors
show ip bgp summary
# All neighbors should show "Established" state
✅ Success Criteria:
• All neighbors in Established state
• Uptime is stable
• Prefix count is non-zero
• All neighbors in Established state
• Uptime is stable
• Prefix count is non-zero
🔍 Step 2: Verify Route Reflection
# On R4 - should see routes from ISPs
show ip bgp
# Look for ORIGINATOR_ID attribute
show ip bgp 0.0.0.0
📝 Knowledge Check
1. What prevents routing loops in route reflector topologies?
2. Which BGP attribute is MOST effective for controlling outbound traffic from your AS?
3. Why must you configure "next-hop-self" on edge routers for iBGP neighbors?