Ticket#4 – BGP Route Not Installing in RIB – Path Attributes and Fix [CCNP Enterprise]

Problem Summary

A network engineer noticed that a BGP route was visible in the BGP table (show ip bgp) but not getting installed in the routing table (RIB) on a core router connected to multiple ISPs.

Traffic toward the advertised prefix was getting dropped. Despite the BGP session being established, the preferred route was not visible in show ip route.

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Symptoms Observed

• BGP route seen in show ip bgp
• Route not present in show ip route
• BGP session was ESTABLISHED
• No explicit route filtering configured
• Ping/traceroute toward destination IP failed
• Redistribution into IGP was not taking place

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Root Cause Analysis

When a BGP route appears in the BGP table but is missing from the RIB, it’s usually due to one of the following:

Most Common Causes:

• Higher Administrative Distance route exists (like static or connected)
• Invalid NEXT_HOP
• Route is not the best BGP path
• Route is marked as inaccessible
• Route is suppressed by RIB constraints

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The Fix

Let’s walk through step-by-step diagnostics and the final fix applied.

Step 1: Verify BGP Route Exists

show ip bgp <prefix>

Step 2: Check If Installed in Routing Table

show ip route <prefix>

If not present, continue…

Step 3: Verify Administrative Distance Conflict

show ip route <prefix>

Look for a connected/static/OSPF/EIGRP route overriding BGP

Step 4: Check Next-Hop Reachability

show ip bgp <prefix>
show ip route <next-hop>

If next-hop unreachable → BGP won’t install it in RIB

Step 5: Force Next-Hop Self (if needed for eBGP)

router bgp 65000
  neighbor x.x.x.x next-hop-self

Step 6: Check for RIB Filtering / Suppression

• BGP route-map might deny installation
• Check for maximum-paths, inbound filters, or route suppression

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EVE-NG Lab Topology

Lab Setup:

Device	Role	AS	Notes
R1	ISP-1	65001	Advertises 100.1.1.0/24
R2	Core	65000	Receives route, not in RIB
R3	ISP-2	65002	Competing route via R3

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Verification Commands

Purpose	Command	Expected Output
See if BGP learned route	show ip bgp <prefix>	Entry present with valid attributes
See if route in RIB	show ip route <prefix>	Should show BGP or missing if not in RIB
Check next-hop reachability	ping <next-hop> / show ip route	Should be reachable
See which route is best	show ip bgp (look for >)	Only best route installs to RIB
See AD precedence	show ip route	Lower AD route may override BGP

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Key Takeaways

• BGP routes in BGP table ≠ Installed in RIB
• Always check next-hop reachability
• Best path selection matters for RIB install
• Competing static or IGP routes can suppress BGP
• Administrative Distance of BGP = 20 (eBGP), 200 (iBGP)

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Best Practice / Design Tips

• Always configure next-hop-self for iBGP
• Use maximum-paths carefully in load sharing
• Redistribute BGP into IGP with proper route-maps
• Use loopback interfaces for peerings when possible
• Monitor route installation via syslog/snmp traps

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FAQs

1. Why is my BGP route not in the routing table?

Answer:
Because either it’s not the best path, the next-hop is unreachable, or another route with lower AD is already installed.

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2. What’s the administrative distance of BGP?

Answer:
eBGP: 20

iBGP: 200

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3. What does > mean in the BGP table?

Answer:
It means the route is the best path and eligible to be installed in the RIB.

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4. How can I check if a static route is overriding BGP?

Answer:

show ip route <prefix>

If static/connected/OSPF route is there, BGP won’t install.

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5. Does next-hop need to be reachable for BGP route to be in RIB?

Answer:
Yes. If next-hop is unreachable, BGP will not install the route.

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6. How to fix next-hop issues in iBGP?

Answer:
Use next-hop-self on the iBGP router:

router bgp 65000
 neighbor 10.0.0.1 next-hop-self

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7. Can BGP show a route that is not installed in RIB?

Answer:
Yes. It can be seen in show ip bgp but not in show ip route.

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8. How to check which BGP route is best?

Answer:
Use:

show ip bgp <prefix>

The > symbol indicates the best path.

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9. What if two BGP routes are equal?

Answer:
You can enable load balancing using:

maximum-paths eibgp 2

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10. Why does iBGP route not install even if it’s best?

Answer:
Because next-hop is not reachable or synchronization is enabled (older IOS versions).

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11. Can I manually install a specific BGP route?

Answer:
No. Only best route chosen by BGP is installed automatically.

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12. Does route filtering affect route installation?

Answer:
Yes. Route-maps or prefix-lists applied inbound may prevent the route from installing.

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13. How to make sure BGP routes are redistributed into IGP?

Answer:

router ospf 1
 redistribute bgp 65000 subnets route-map <map>

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14. How to log BGP route installation issues?

Answer:
Enable:

debug ip routing
debug ip bgp

(Use with caution in production)

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15. Can BGP advertise a route that is not in RIB?

Answer:
No. BGP will only advertise routes that exist in the RIB unless network <prefix> command is used with a matching route.

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YouTube Link

Watch the Complete CCNP Enterprise: BGP Route Not Installing in RIB – Path Attributes and Fix Demo & Explanation on our channel:

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Final Note

Understanding how to differentiate and implement BGP Route Not Installing in RIB – Path Attributes and Fix is critical for anyone pursuing CCNP Enterprise (ENCOR) certification or working in enterprise network roles. Use this guide in your practice labs, real-world projects, and interviews to show a solid grasp of architectural planning and CLI-level configuration skills.

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