📡 show ip protocols – Viewing and Troubleshooting Routing Protocols

Welcome, future network professionals!
Understanding show ip protocols will take your CCNA exam preparation—and your real-world troubleshooting skills—to the next level. Master this command, and you’ll unlock the secrets behind how routers learn, share, and select the best paths in any network. Let’s dive in step-by-step!

Purpose of `show ip protocols` Command

Definition: show ip protocols is a Cisco IOS command that displays a summary of all IPv4 routing protocols active on the device, including their key operational parameters.

When/Why to Use:

Monitor routing protocol status and verify which protocols are active (OSPF, EIGRP, RIP, etc.).
Troubleshoot routing issues, filters, timers, and redistribution.
Get a quick overview of timers, networks included, router IDs, and more.

Information Displayed by the Command

Router# show ip protocols

Routing Protocol is "eigrp 10"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Default networks flagged in outgoing updates
  Routing for Networks:
    192.168.1.0
    10.1.1.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    192.168.1.2     90           00:00:22
  Distance: 90

Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 1.1.1.1
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    10.10.10.0 0.0.0.255 area 0
  Routing Information Sources:
    Gateway         Distance      Last Update
    10.10.10.2      110          00:00:10
  Distance: 110
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

Key Details and How to Use Them

Section	What to Look For	Actions / Importance
Routing Protocol is	EIGRP, OSPF, RIP, etc.	Which protocols are running
Router ID	Router’s unique ID (OSPF/EIGRP)	Must be unique in the topology; used in neighbor relationships
Networks	Network statements listed (e.g., 192.168.1.0/24)	Which interfaces/subnets are included in routing
Interfaces	Interfaces under “Routing for Networks”	Verify participation in routing
Distance	Administrative distance (e.g., 90 for EIGRP, 110 for OSPF)	Determines protocol preference in the routing table (lower is better)
Routing Information Sources	Neighbor routers’ IPs, their AD, last update time	Should see expected neighbors with recent update times
Timers	Protocol-specific (Hello, Dead, etc.)	Timer mismatches can break adjacencies
Outgoing/Incoming filter lists	Distribute-list, route-map, or ACL	Filters can block needed updates
Passive Interface	Interfaces set as passive	No routing updates sent—common exam topic
Redistribution Information	Is redistribution active?	Critical when multiple protocols coexist
Default Originate	Is default route advertised?	“Gateway of last resort” distribution
Protocol Version Details	OSPF areas, EIGRP AS, RIP version	Troubleshooting protocol mismatches

How to Use This Command for Troubleshooting

Check which protocols are running if routes are missing.
Confirm the correct networks are included under each protocol.
Verify timers match on all routers in the same area/domain (e.g., OSPF Hello/Dead).
Look for passive interfaces—routing won’t work if the required interface is passive.
Check for filters or redistribution if some routes are not being learned or advertised.
Examine “Routing Information Sources” to confirm neighbors are present and updating.
Use administrative distance to resolve route preference conflicts.

Example: Troubleshooting Scenario

Scenario: John cannot reach 10.10.10.0/24, which should be advertised by OSPF.

Run show ip protocols
Is OSPF listed? Is 10.10.10.0 included under “Routing for Networks”?
Is Router ID unique and correct? Are timers matching neighbor routers?
Is the correct interface listed as passive (should not be passive if adjacency is needed)?
Are filters (distribute-list, route-map, ACL) blocking the update?
For redistribution: Is OSPF getting updates from other protocols (EIGRP, RIP, etc.)?

Quick Reference: Interpreting `show ip protocols` Output

Section	What to Check	What It Means / Next Steps
Routing Protocol is	Presence of protocol	Should match expected protocols (EIGRP, OSPF, etc.)
Router ID	Unique ID for OSPF/EIGRP	Should not duplicate another router
Routing for Networks	All required subnets included?	Add missing networks if required
Routing Information Sources	Neighbor IPs and update times	No/lost updates = possible neighbor issue
Timers	Hello/Dead/Update intervals	Mismatched timers = no adjacency
Passive Interface	Check which are passive	Don’t set passive on neighbor-facing interfaces
Redistribution Info	Are protocols redistributing?	Set correct metrics/route-maps if needed
Filter Lists	Outgoing/incoming filter lists	Remove or adjust if blocking needed routes
Default Originate	Advertising default route?	Ensure for internet/GW reachability

Practice Lab Scenario: Troubleshooting with `show ip protocols`

Lab Topology:
Router1: OSPF & EIGRP enabled
Router2: OSPF neighbor
Router3: EIGRP neighbor

Run show ip protocols on Router1
Verify OSPF is running and 10.10.30.0 is under “Routing for Networks”
Confirm Router ID and neighbor (Routing Information Sources) are correct
Check OSPF timers against Router2
Ensure the Router1–Router2 interface is not passive
Check for filters or redistribution issues
Correct any missing/misconfigured network, timers, or filters

Exam Tips and Key Points

Always check “Passive Interface”—most overlooked exam trick.
Understand how AD (Administrative Distance) determines route preference.
Match networks and timers to your topology and protocol requirements.
Use show ip protocols as your first check for protocol/neighbor/configuration problems before digging into the routing table.

Show IP Protocols Quiz

1. What is the primary purpose of the `show ip protocols` command?

A. To display MAC address table information B. To display an overview of all active IPv4 routing protocols on the device C. To configure routing protocols D. To show interface status and errors

Correct answer is B. This command shows all active IPv4 routing protocols and their details on the device.

2. What unique identifier is shown for protocols like OSPF and EIGRP in `show ip protocols` output?

A. MAC Address B. IP Address of Gateway C. Subnet Mask D. Router ID

Correct answer is D. Router ID uniquely identifies the router in OSPF/EIGRP protocols.

3. In the `show ip protocols` output, what do the timer intervals such as Hello and Dead relate to?

A. Protocol-specific timing for neighbor discovery and loss detection B. Time to process packets C. Time between IP address renewals D. Duration to reset the router

Correct answer is A. Hello and Dead timers control neighbor adjacency and failure detection in routing protocols.

4. What does the “Routing for Networks” section indicate in the `show ip protocols` output?

A. The current routing table B. Interfaces that are down C. Networks included in the routing updates D. VLAN assignments

Correct answer is C. This section lists networks that the routing protocol advertises and participates in.

5. Which administrative distance (AD) value corresponds to OSPF by default?

A. 90 B. 110 C. 120 D. 0

Correct answer is B. OSPF's default administrative distance is 110.

6. What does it mean when an interface is listed as a “passive interface” in the `show ip protocols` output?

A. It participates in routing but does not send routing updates B. It is administratively down C. It is a trunk port D. It is disabled for routing completely

Correct answer is A. Passive interfaces do not send routing updates but still participate in the routing protocol.

7. If routes from one routing protocol are advertised into another, which feature is being used?

A. Route summarization B. Default routing C. Redistribution D. Route filtering

Correct answer is C. Redistribution allows routes to be advertised between different protocols.

8. Which of the following is a reason to check the `show ip protocols` command when troubleshooting?

A. To check MAC addresses on interfaces B. To check VLAN trunking status C. To reset router interfaces D. To verify which routing protocols are running and their configuration

Correct answer is D. This command helps verify active routing protocols and their details for troubleshooting.

9. What could happen if timer intervals (Hello, Dead) do not match between routing neighbors?

A. Routers will forward traffic incorrectly B. Neighbor adjacency will fail, causing routing issues C. Routing protocols will redistribute incorrectly D. Interfaces will go down

Correct answer is B. Timer mismatches prevent neighbor relationships from forming properly.

10. In the provided troubleshooting scenario, what should be checked first if a network is missing from OSPF?

A. If the missing network is included in the OSPF network statements B. If the MAC address table is cleared C. If VLAN trunking is enabled D. If static routes are configured

Correct answer is A. Missing OSPF networks are often due to lack of inclusion in the network statements.

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📡 show ip protocols – Viewing and Troubleshooting Routing Protocols

Purpose of show ip protocols Command