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Module 53
Troubleshooting Routing Issues
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# 📘 CCNA 200-301 - Video 53: Troubleshooting Routing Issues ## Deep Study Notes --- ## 📌 Learning Objectives By the end of this video, you should understand: - Common routing issues and their causes - Static route troubleshooting - OSPF troubleshooting (neighbors, areas, LSAs) - EIGRP troubleshooting (neighbors, DUAL, metrics) - Routing protocol redistribution issues - Routing table analysis - Troubleshooting tools and commands --- ## 🧠 Core Concepts ### 1. Common Routing Issues Overview ``` ┌─────────────────────────────────────────────────────────────────────────────┐ │ COMMON ROUTING ISSUES │ ├─────────────────────────────────────────────────────────────────────────────┤ │ │ │ STATIC ROUTING ISSUES: │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Missing routes │ │ │ │ • Incorrect next-hop │ │ │ │ • Recursive routing │ │ │ │ • Floating static route not working │ │ │ │ • Default route missing │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ OSPF ISSUES: │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Neighbors not forming │ │ │ │ • DR/BDR election issues │ │ │ │ • Area mismatch │ │ │ │ • Network type mismatch │ │ │ │ • Authentication failure │ │ │ │ • Stub area issues │ │ │ │ • Route not advertised │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ EIGRP ISSUES: │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Neighbors not forming │ │ │ │ • AS number mismatch │ │ │ │ • K values mismatch │ │ │ │ • Auto-summarization issues │ │ │ │ • Stub issues │ │ │ │ • Metric calculation issues │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ REDISTRIBUTION ISSUES: │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Missing seed metrics │ │ │ │ • Routing loops │ │ │ │ • Suboptimal routing │ │ │ │ • Filtering issues │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ └─────────────────────────────────────────────────────────────────────────────┘ ``` --- ### 2. Routing Table Analysis **Routing Table Codes:** | Code | Meaning | |------|---------| | C | Connected (directly attached network) | | S | Static route | | O | OSPF intra-area | | O IA | OSPF inter-area | | O E1/E2 | OSPF external | | D | EIGRP internal | | D EX | EIGRP external | | R | RIP | | B | BGP | | L | Local (host route) | ```cisco ! Display routing table Router# show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route Gateway of last resort is 10.1.1.1 to network 0.0.0.0 C 10.1.1.0/30 is directly connected, GigabitEthernet0/0 L 10.1.1.1/32 is directly connected, GigabitEthernet0/0 C 192.168.1.0/24 is directly connected, GigabitEthernet0/1 L 192.168.1.1/32 is directly connected, GigabitEthernet0/1 S 172.16.0.0/16 [1/0] via 10.1.1.2 O 10.2.2.0/24 [110/2] via 10.1.1.2, 00:01:23, GigabitEthernet0/0 D 192.168.2.0/24 [90/307200] via 10.1.1.2, 00:01:23, GigabitEthernet0/0 S* 0.0.0.0/0 [1/0] via 10.1.1.1 ``` **Routing Table Troubleshooting:** | Observation | Possible Issue | |-------------|----------------| | Missing expected routes | Routing protocol not advertising, neighbor issues, filtering | | Route with wrong next-hop | Static route misconfigured, routing protocol metric issue | | No default route | Missing default route, DHCP not providing gateway | | Multiple routes to same destination | ECMP (if same metric) or routing issue | | Route not used | Higher administrative distance, route not valid | --- ### 3. Static Route Troubleshooting ```cisco ! Display static routes Router# show ip route static S 172.16.0.0/16 [1/0] via 10.1.1.2 S 10.2.0.0/16 [1/0] via 10.1.1.3 S* 0.0.0.0/0 [1/0] via 10.1.1.1 ! Check if next-hop is reachable Router# show ip route 10.1.1.2 ! Ping next-hop Router# ping 10.1.1.2 ! Check recursive routing Router# show ip route 10.1.1.2 Router# show ip route 10.1.1.2 ``` **Common Static Route Issues:** | Issue | Symptom | Solution | |-------|---------|----------| | **Next-hop unreachable** | Route not in routing table | Ensure next-hop reachable via another route | | **Incorrect next-hop** | Packets dropped | Verify next-hop IP address | | **Missing default route** | Internet access fails | Add default route: `ip route 0.0.0.0 0.0.0.0 [next-hop]` | | **Floating static not used** | Primary route down, backup not active | Check AD, ensure primary route removed | | **Recursive routing** | Route points to itself | Use exit interface instead of next-hop | --- ### 4. OSPF Troubleshooting **OSPF Neighbor States:** | State | Meaning | |-------|---------| | **Down** | No hello received | | **Attempt** | Manual neighbor configuration (NBMA) | | **Init** | Hello received, but no neighbor information | | **2-Way** | Bidirectional communication established | | **Exstart** | Master/slave election, ready to exchange | | **Exchange** | Exchanging database description (DBD) packets | | **Loading** | Exchanging link-state requests (LSR) | | **Full** | Fully adjacent (database synchronized) | ``` ┌─────────────────────────────────────────────────────────────────────────────┐ │ OSPF TROUBLESHOOTING FLOW │ ├─────────────────────────────────────────────────────────────────────────────┤ │ │ │ START: OSPF neighbors not forming │ │ │ │ │ ▼ │ │ Check physical connectivity │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Interface up/up? │ │ │ │ • Can ping neighbor? │ │ │ │ If NO → Fix physical layer │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ │ ▼ │ │ Check OSPF configuration │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Same area ID? │ │ │ │ • Same network type? │ │ │ │ • Same hello/dead timers? │ │ │ │ • MTU match? │ │ │ │ If NO → Fix configuration │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ │ ▼ │ │ Check authentication │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Same authentication type? │ │ │ │ • Same password/key? │ │ │ │ If NO → Fix authentication │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ │ ▼ │ │ Check DR/BDR election (broadcast networks) │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • DR/BDR elected? │ │ │ │ • Priority 0 routers not participating? │ │ │ │ If NO → Check priorities │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ │ ▼ │ │ Check OSPF routes │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Routes in routing table? │ │ │ │ • LSAs in database? │ │ │ │ If NO → Check network statements, passive interfaces │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ └─────────────────────────────────────────────────────────────────────────────┘ ``` **OSPF Verification Commands:** ```cisco ! Check OSPF neighbors Router# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 1 FULL/DR 00:00:35 10.1.1.2 GigabitEthernet0/0 3.3.3.3 1 FULL/BDR 00:00:32 10.1.1.3 GigabitEthernet0/0 ! Check OSPF interfaces Router# show ip ospf interface GigabitEthernet0/0 is up, line protocol is up Internet Address 10.1.1.1/30, Area 0 Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1 Transmit Delay is 1 sec, State DR, Priority 1 Designated Router (ID) 1.1.1.1, Interface address 10.1.1.1 Backup Designated router (ID) 2.2.2.2, Interface address 10.1.1.2 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:03 Neighbor Count is 2, Adjacent neighbor count is 2 ! Check OSPF database Router# show ip ospf database OSPF Router with ID (1.1.1.1) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 123 0x80000002 0x1234 3 2.2.2.2 2.2.2.2 110 0x80000003 0x5678 2 ! Check OSPF routes Router# show ip route ospf O 10.2.2.0/24 [110/2] via 10.1.1.2, 00:01:23, GigabitEthernet0/0 O 192.168.2.0/24 [110/3] via 10.1.1.2, 00:01:23, GigabitEthernet0/0 ``` **Common OSPF Issues:** | Issue | Symptom | Solution | |-------|---------|----------| | **Neighbor stuck in Exstart/Exchange** | MTU mismatch | Configure same MTU on both sides | | **Neighbor stuck in Init** | Hello not received | Check interface state, multicast reachability | | **Neighbor stuck in 2-Way** | DR/BDR election not complete | Check priorities, ensure at least one router can be DR | | **No routes** | OSPF neighbors Full but no routes | Check network statements, passive interfaces | | **Authentication failure** | "Authentication failed" in logs | Verify authentication type and key | | **Area mismatch** | Neighbors form, but routes missing | Check area configuration on interfaces | --- ### 5. OSPF Network Type Issues ```cisco ! Check OSPF network type Router# show ip ospf interface gigabitEthernet 0/0 | include Type Network Type BROADCAST, Cost: 1 ! Change network type Router(config)# interface gigabitEthernet 0/0 Router(config-if)# ip ospf network point-to-point ``` **Network Type Troubleshooting:** | Issue | Symptom | Solution | |-------|---------|----------| | **Broadcast network with no DR** | No adjacency | Verify DR election, ensure priorities not 0 | | **NBMA without neighbor statements** | No neighbors | Configure `neighbor` statements | | **Point-to-multipoint on broadcast** | Suboptimal routes | Use correct network type | --- ### 6. EIGRP Troubleshooting **EIGRP Neighbor States:** | State | Meaning | |-------|---------| | **Down** | No hello received | | **Pending** | Neighbor discovered, waiting for update | | **Up** | Fully operational | ``` ┌─────────────────────────────────────────────────────────────────────────────┐ │ EIGRP TROUBLESHOOTING FLOW │ ├─────────────────────────────────────────────────────────────────────────────┤ │ │ │ START: EIGRP neighbors not forming │ │ │ │ │ ▼ │ │ Check physical connectivity │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Interface up/up? │ │ │ │ • Can ping neighbor? │ │ │ │ If NO → Fix physical layer │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ │ ▼ │ │ Check EIGRP configuration │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Same AS number? │ │ │ │ • Same K values? │ │ │ │ • Network statement includes interface? │ │ │ │ If NO → Fix configuration │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ │ ▼ │ │ Check authentication │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Same authentication type? │ │ │ │ • Same key? │ │ │ │ If NO → Fix authentication │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ │ ▼ │ │ Check auto-summarization │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Auto-summary enabled? │ │ │ │ • Discontiguous networks? │ │ │ │ If YES → Disable auto-summary │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ │ ▼ │ │ Check EIGRP stub │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Stub router receiving queries? │ │ │ │ If YES → Configure stub appropriately │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ └─────────────────────────────────────────────────────────────────────────────┘ ``` **EIGRP Verification Commands:** ```cisco ! Check EIGRP neighbors Router# show ip eigrp neighbors EIGRP-IPv4 neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq 0 10.1.1.2 Gi0/0 12 00:01:23 1 100 0 15 1 10.1.2.2 Gi0/1 14 00:00:45 2 200 0 12 ! Check EIGRP topology Router# show ip eigrp topology EIGRP-IPv4 Topology Table for AS(100)/ID(1.1.1.1) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 10.1.1.0/24, 1 successors, FD is 281600 via Connected, GigabitEthernet0/0 P 192.168.1.0/24, 1 successors, FD is 307200 via 10.1.1.2 (307200/281600), GigabitEthernet0/0 P 10.2.2.0/24, 2 successors, FD is 284160 via 10.1.1.2 (284160/281600), GigabitEthernet0/0 via 10.1.2.2 (284160/281600), GigabitEthernet0/1 ! Check EIGRP interfaces Router# show ip eigrp interfaces EIGRP-IPv4 Interfaces for AS(100) Xmit Queue PeerQ Mean Pacing Time Multicast Interface Peers Un/Reliable Un/Reliable SRTT Un/Reliable Flow Timer Gi0/0 1 0/0 0/0 1 0/15 0 Gi0/1 1 0/0 0/0 2 0/15 0 ``` **Common EIGRP Issues:** | Issue | Symptom | Solution | |-------|---------|----------| | **AS mismatch** | No neighbors | Configure same AS number | | **K values mismatch** | Neighbors not forming | Configure same K values or default (1,0,1,0,0) | | **Auto-summary** | Routes missing/discontiguous | `no auto-summary` | | **Stub router issues** | Query stuck in Active (SIA) | Configure stub correctly, don't use `receive-only` | | **Passive interface** | No routes advertised | Remove passive interface or add network statement | | **Metric calculation** | Suboptimal routing | Check bandwidth and delay on interfaces | --- ### 7. Route Redistribution Troubleshooting ```cisco ! Check redistribution configuration Router# show ip protocols Routing Protocol is "ospf 1" Redistributing: eigrp 100 Redistributing protocols: eigrp 100 Redistributing: eigrp 100 route-map REDISTRIBUTE ! Check redistributed routes Router# show ip route | include EX D EX 10.1.0.0/16 [170/28160] via 192.168.1.2, 00:01:23, GigabitEthernet0/0 O E2 172.16.0.0/16 [110/20] via 192.168.1.1, 00:01:23, GigabitEthernet0/1 ! Check seed metrics Router# show running-config | include redistribute redistribute eigrp 100 metric 30 subnets ``` **Common Redistribution Issues:** | Issue | Symptom | Solution | |-------|---------|----------| | **Missing seed metric** | Routes not redistributed | Configure seed metric (EIGRP requires metric) | | **Missing subnets keyword** | Only classful routes redistributed | Add `subnets` to OSPF redistribution | | **Routing loops** | Routes flapping | Use route maps with tags to prevent loops | | **Suboptimal routing** | Traffic takes long path | Adjust metrics, use route maps | | **Filtering** | Some routes not redistributed | Check route maps, ACLs | --- ### 8. Inter-VLAN Routing Troubleshooting **Router-on-a-Stick:** ```cisco ! Check subinterfaces Router# show ip interface brief | include Gi0/0 GigabitEthernet0/0 unassigned YES unset up up GigabitEthernet0/0.10 192.168.10.1 YES manual up up GigabitEthernet0/0.20 192.168.20.1 YES manual up up ! Check trunk on switch Switch# show interfaces trunk Port Mode Encapsulation Status Native vlan Gi0/24 on 802.1q trunking 1 ! Verify connectivity Router# ping 192.168.10.10 source 192.168.20.1 ``` **Common Inter-VLAN Routing Issues:** | Issue | Symptom | Solution | |-------|---------|----------| | **Trunk not established** | Subinterfaces up, but no connectivity | Check trunk mode, allowed VLANs | | **Native VLAN mismatch** | Intermittent connectivity | Match native VLAN on both ends | | **Missing encapsulation** | Subinterface down | Configure `encapsulation dot1Q [vlan]` | | **Wrong default gateway** | Can't reach other VLANs | Configure correct gateway on hosts | --- ### 9. Troubleshooting with Debug **Debug Commands (Use with Caution):** ```cisco ! Debug OSPF (use ACL to limit) access-list 100 permit ip host 10.1.1.1 host 10.1.1.2 debug ip ospf events debug ip ospf hello debug ip ospf adj ! Debug EIGRP debug eigrp packets debug eigrp neighbors debug eigrp fsm ! Debug routing (general) debug ip routing ! Debug IP packets (with ACL) debug ip packet 100 ! Turn off all debugging undebug all no debug all ``` **Debugging Best Practices:** ``` ┌─────────────────────────────────────────────────────────────────────────────┐ │ DEBUGGING BEST PRACTICES │ ├─────────────────────────────────────────────────────────────────────────────┤ │ │ │ 1. USE SPECIFIC DEBUG COMMANDS │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • debug ip ospf events (not debug ip ospf all) │ │ │ │ • Use ACLs to limit output │ │ │ │ • Monitor CPU usage during debug │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ 2. KNOW WHEN TO DEBUG │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Low-traffic periods │ │ │ │ • Maintenance windows │ │ │ │ • When other troubleshooting fails │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ 3. CAPTURE OUTPUT │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • Log to buffer: logging buffered 16384 │ │ │ │ • Copy output for later analysis │ │ │ │ • Use terminal monitor to see output remotely │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ │ 4. DISABLE DEBUG WHEN DONE │ │ ┌─────────────────────────────────────────────────────────────────────┐ │ │ │ • undebug all │ │ │ │ • no debug all │ │ │ └─────────────────────────────────────────────────────────────────────┘ │ │ │ └─────────────────────────────────────────────────────────────────────────────┘ ``` --- ## 🔧 Complete Configuration Examples ### Lab 1: OSPF Neighbor Troubleshooting ```cisco ! Step 1: Check interface status show ip interface brief ! Step 2: Check OSPF neighbor show ip ospf neighbor ! Step 3: Check OSPF interface show ip ospf interface ! Step 4: Check MTU show interfaces gigabitEthernet 0/0 | include MTU ! Step 5: Debug OSPF events debug ip ospf events ``` --- ### Lab 2: EIGRP Troubleshooting ```cisco ! Step 1: Check EIGRP neighbors show ip eigrp neighbors ! Step 2: Check EIGRP topology show ip eigrp topology ! Step 3: Check EIGRP interfaces show ip eigrp interfaces ! Step 4: Check auto-summary show running-config | include auto-summary ! Step 5: Debug EIGRP debug eigrp packets ``` --- ### Lab 3: Static Route Troubleshooting ```cisco ! Step 1: Display static routes show ip route static ! Step 2: Check next-hop reachability show ip route 10.1.1.2 ! Step 3: Ping next-hop ping 10.1.1.2 ! Step 4: Check recursive routing show ip route 10.1.1.2 ! Step 5: Add missing route ip route 10.1.1.0 255.255.255.0 10.1.1.1 ``` --- ### Lab 4: Redistribution Troubleshooting ```cisco ! Step 1: Check routing protocols show ip protocols ! Step 2: Check redistributed routes show ip route | include EX|E2 ! Step 3: Check redistribution configuration show running-config | include redistribute ! Step 4: Add missing seed metric router eigrp 100 redistribute ospf 1 metric 10000 100 255 1 1500 router ospf 1 redistribute eigrp 100 subnets metric 30 ``` --- ## ✅ Exam Tips (For CCNA 200-301) | Topic | What Cisco Tests | |-------|------------------| | **Routing Table** | Interpret codes, metrics, administrative distance | | **OSPF States** | Down, Init, 2-Way, Exstart, Exchange, Loading, Full | | **EIGRP States** | Down, Pending, Up | | **Neighbor Requirements** | Same AS (EIGRP), same area (OSPF), reachability | | **Redistribution** | Seed metrics, subnets keyword | | **Inter-VLAN Routing** | Subinterfaces, trunk configuration | ### Common Exam Scenarios: **Scenario 1:** "OSPF neighbors are stuck in Exstart/Exchange state. What is the most likely cause?" - **Answer:** MTU mismatch between neighbors **Scenario 2:** "EIGRP neighbors are not forming. What should be checked first?" - **Answer:** AS numbers must match, interfaces must be up **Scenario 3:** "Routes are being redistributed into OSPF, but only classful networks appear. What is missing?" - **Answer:** The `subnets` keyword in redistribution command --- ## 📝 Summary (1-Minute Revision) ``` ROUTING TROUBLESHOOTING: ROUTING TABLE: ├── show ip route - View all routes ├── show ip route [network] - View specific route ├── C: Connected, S: Static, O: OSPF, D: EIGRP ├── O IA: Inter-area, O E1/E2: External ├── D EX: EIGRP external STATIC ROUTES: ├── ip route [network] [mask] [next-hop] ├── Check next-hop reachability ├── Use exit interface to avoid recursion └── Floating static: different AD OSPF TROUBLESHOOTING: ├── show ip ospf neighbor - Check adjacency ├── show ip ospf interface - Check timers, network type ├── show ip ospf database - Check LSAs ├── States: Down → Init → 2-Way → Exstart → Exchange → Loading → Full └── Common issues: MTU mismatch, area mismatch, authentication EIGRP TROUBLESHOOTING: ├── show ip eigrp neighbors - Check neighbors ├── show ip eigrp topology - Check routes ├── show ip eigrp interfaces - Check enabled interfaces ├── Requirements: Same AS, same K values └── Auto-summary: disable with no auto-summary REDISTRIBUTION: ├── OSPF: redistribute [protocol] subnets metric [value] ├── EIGRP: redistribute [protocol] metric [bw] [delay] [rel] [load] [mtu] ├── Missing seed metric = routes not redistributed └── Missing subnets = only classful routes DEBUGGING: ├── debug ip ospf events ├── debug ip eigrp ├── debug ip routing ├── Use ACLs to limit output └── undebug all to disable ``` --- ## 🧪 Practice Questions **1. What does the routing table code "O IA" indicate?** - A) OSPF intra-area route - B) OSPF inter-area route - C) OSPF external route - D) OSPF NSSA route <details> <summary>Answer</summary> <b>B) OSPF inter-area route</b> - O IA indicates OSPF inter-area routes. </details> **2. OSPF neighbors are stuck in Exstart/Exchange state. What is the most likely cause?** - A) Authentication failure - B) MTU mismatch - C) Area mismatch - D) Hello timer mismatch <details> <summary>Answer</summary> <b>B) MTU mismatch</b> - MTU mismatch causes Exstart/Exchange state. </details> **3. Which command displays EIGRP neighbors?** - A) `show ip ospf neighbor` - B) `show ip eigrp neighbors` - C) `show ip route` - D) `show eigrp topology` <details> <summary>Answer</summary> <b>B) `show ip eigrp neighbors`</b> - Displays EIGRP neighbor table. </details> **4. What is the default administrative distance for OSPF?** - A) 90 - B) 110 - C) 120 - D) 170 <details> <summary>Answer</summary> <b>B) 110</b> - OSPF default AD is 110. </details> **5. What does the OSPF neighbor state "Full" indicate?** - A) Neighbor not responding - B) Fully adjacent, database synchronized - C) Exchanging routes - D) DR/BDR election in progress <details> <summary>Answer</summary> <b>B) Fully adjacent, database synchronized</b> - Full state indicates full adjacency. </details> **6. Which command is used to disable EIGRP auto-summarization?** - A) `no auto-summary` - B) `disable auto-summary` - C) `auto-summary off` - D) `no summary` <details> <summary>Answer</summary> <b>A) `no auto-summary`</b> - Disables automatic summarization in EIGRP. </details> **7. A static route appears in the routing table but traffic is not forwarded. What could be the issue?** - A) Next-hop unreachable - B) Administrative distance too high - C) Metric too high - D) Route is a summary route <details> <summary>Answer</summary> <b>A) Next-hop unreachable</b> - Next-hop must be reachable for route to be used. </details> **8. What is required for EIGRP neighbors to form?** - A) Same area ID - B) Same AS number - C) Same router ID - D) Same metric type <details> <summary>Answer</summary> <b>B) Same AS number</b> - EIGRP requires the same autonomous system number. </details> **9. Which command shows OSPF LSAs?** - A) `show ip ospf` - B) `show ip ospf database` - C) `show ip ospf neighbor` - D) `show ip route ospf` <details> <summary>Answer</summary> <b>B) `show ip ospf database`</b> - Displays OSPF link-state database. </details> **10. When redistributing OSPF into EIGRP, what is required?** - A) Subnets keyword - B) Metric values - C) Route map - D) Default route <details> <summary>Answer</summary> <b>B) Metric values</b> - EIGRP requires explicit metric for redistributed routes. </details> **11. What does the routing table code "D EX" indicate?** - A) EIGRP internal route - B) EIGRP external route - C) OSPF external route - D) Static route <details> <summary>Answer</summary> <b>B) EIGRP external route</b> - D EX indicates redistributed (external) EIGRP routes. </details> **12. Which debug command helps troubleshoot OSPF adjacency issues?** - A) `debug ip ospf events` - B) `debug ip routing` - C) `debug ip packet` - D) `debug ip ospf flushes` <details> <summary>Answer</summary> <b>A) `debug ip ospf events`</b> - Shows OSPF adjacency events. </details> --- ## 📌 Next Steps After completing Video 53, you should be ready for: - **Video 54:** Troubleshooting WAN Issues - **Video 55:** Troubleshooting Wireless Issues **Lab Practice:** 1. Configure OSPF with issues and troubleshoot 2. Configure EIGRP with auto-summary issues 3. Create static route issues and fix 4. Configure redistribution and troubleshoot 5. Practice with debug commands --- **Ready for Video 54?** Share the link or say "next" and I'll continue with Troubleshooting WAN Issues. I'll continue with **Video 54: Troubleshooting WAN Issues** based on the standard CCNA 200-301 curriculum. ---