Cisco Router Show Commands

Cisco router runs on an operating system called the IOS (Internetwork Operating System).To enable the administrator to retrieve information and change the device’s settings. One of the most powerful command in IOS is Show. To know All Show Commands in Cisco Switch and Router keep reading this article till the end. All these commands retrieve information in the Cisco switch and router. These are followings:

Cisco Router Show Commands

S.No. Cisco IOS Show Command Displays statistics for all interfaces

1 R1#show interfaces Displays statistics for all interfaces

2 R1#show interface fa0/0 Displays statistics of fa0/0 interface.

You may use other interfaces also.

3 R1#show ip interface brief Displays a summary of all IPv4 interfaces, including

status and IPv4 address assigned in router 

4 R1#show ipv6 interface brief Displays a summary of all IPv6 interfaces, including

status and IPv6 address assigned in router 

5 R1#show controllers serial 1/0 Displays statistics for interface hardware serial 1/0.

Statistics display if the clock rate is set and

if the cable is DCE, DTE, or not attached

6 R1#show clock Displays the system clock of the router 

7 R1#show hosts Displays the configured hostnames and their

corresponding IP addresses of the router 

8 R1#show users Displays all users connected to the router

9 R1#show history Displays history of Cisco IOS commands used

10 R1#show flash Displays info about Flash memory

11 R1#show version Displays info about loaded Cisco IOS software

12 R1#show arp Displays the ARP table of the router 

ARP table is the table which contains the

resolved IPv4 address to MAC address mappings.

13 R1#show protocols Displays status of configured Layer 3 protocols

14 R1#show startup-config Displays configuration saved in NVRAM

15 R1#show running-config Displays configuration currently running in RAM

16 R1#show ip route Displays the IPv4 routing table of the router 

17 R1#show ipv6 route show ipv6 route

Cisco Switch Show Commands

S.No. Cisco IOS Show Command Displays statistics for all interfaces

1         Sw1#show arp To display entries in the ARP table, use the switch show arp command in privileged EXEC mode.

2 Sw1#show access-lists List access lists

3 Sw1# show boot show boot attributes

4 Sw1#show cdp CDP information

5 Sw1#show clock Display the system clock

6 Sw1#show crypto Encryption module

7 Sw1#show dtp  DTP information

8 Sw1#show  etherchannel EtherChannel information

9 Sw1#show flash: display information about flash: file system

10 Sw1#show history  Display the session command history

11 Sw1#show hosts  IP domain-name, lookup style, nameservers, and host table

12 Sw1#show interfaces Interface status and configuration

13 Sw1#show ip IP information

14 Sw1#show ipv6 IPv6 information

15 Sw1#show logging Show the contents of logging buffers

16 Sw1#show mac MAC configuration

17 Sw1#show mac-address-table MAC forwarding table

18 Sw1#show  mls Show MultiLayer Switching information

19 Sw1#show port-security  Show secure port information

20 Sw1#show privilege Show current privilege level

21 Sw1#show processes Active process statistics

22 Sw1#show running-config Current operating configuration

23 Sw1#show sessions Information about Telnet connections

24 Sw1#show snmp snmp statistics

25 Sw1#show spanning-tree Spanning tree topology

26 Sw1#show ssh Status of SSH server connections

27 Sw1#show startup-config Contents of startup configuration

28 Sw1#show storm Show storm control configuration

29 Sw1#show tcp Status of TCP connections

30 Sw1#show tech-support Show system information for Tech-Support

31 Sw1#show terminal Display terminal configuration parameters

32 Sw1#show users Display information about terminal lines

33 Sw1#show version System hardware and software status

34 Sw1#show vlan VTP VLAN status

35 Sw1#show vtp VTP information

[19:41, 04/12/2022] +91 96549 88639: https://drive.google.com/file/d/1mZGkW65NG20tlpdhTlsm8jeAjj9h0o42/view?usp=sharing

[20:17, 11/12/2022] +91 96549 88639: https://drive.google.com/file/d/1RDiqsFyOOnDnsKw7ih6-U0YkHHChng2z/view?usp=sharing

[20:17, 11/12/2022] +91 96549 88639: Open shortest path first (OSPF) is a link-state routing protocol that is used to find the best path between the source and the destination router using its own shortest path first (SPF) algorithm. A link-state routing protocol is a protocol that uses the concept of triggered updates, i.e., if there is a change observed in the learned routing table then the updates are triggered only, not like the distance-vector routing protocol where the routing table is exchanged at a period of time. 

Open shortest path first (OSPF) is developed by Internet Engineering Task Force (IETF) as one of the Interior Gateway Protocol (IGP), i.e., the protocol which aims at moving the packet within a large autonomous system or routing domain. It is a network layer protocol that works on protocol number 89 and uses AD value 110. OSPF uses multicast address 224.0.0.5 for normal communication and 224.0.0.6 for update to designated router(DR)/Backup Designated Router (BDR). 

Criteria – 

To form neighbourship in OSPF, there is a criterion for both the routers:  

1. It should be present in the same area.

2. The router I’d be unique.

3. The subnet mask should be the same. 

4. Hello, and the dead timer should be the same. 

5. The stub flag must match. 

6. Authentication must match. 

 

OSPF supports NULL, plain text, MD5 authentication. 

Note – Both the routers (neighbors) should have some type of authentication enabled. e.g- if one neighbor has MD5 authentication enabled then others should also have MD5 authentication enabled. 

OSPF messages – 

OSPF uses certain messages for the communication between the routers operating OSPF. 

• Hello message – 

These are keep-alive messages used for neighbor discovery /recovery. These are exchanged every 10 seconds. This includes the following information: Router I’d, Hello/dead interval, Area I’d, Router priority, DR and BDR IP address, authentication data. 

• Database Description (DBD) – 

It is the OSPF route of the router. This contains the topology of an AS or an area (routing domain). 

• Link state request (LSR) – 

When a router receives DBD, it compares it with its own DBD. If the DBD received has some more updates than its own DBD then LSR is being sent to its neighbor. 

• Link state update (LSU) – 

When a router receives LSR, it responds with an LSU message containing the details requested. 

• Link state acknowledgement – 

This provides reliability to the link-state exchange process. It is sent as the acknowledgement of LSU. 

• Link state advertisement (LSA) – 

It is an OSPF data packet that contains link-state routing information, shared only with the routers to which adjacency has been formed. 

Note – Link State Advertisement and Link State Acknowledgement both are different messages. 

Timers – 

• Hello timer – 

The interval in which the OSPF router sends a hello message on an interface. It is 10 seconds by default. 

• Dead timer – 

The interval in which the neighbor will be declared dead if it is not able to send the hello packet. It is 40 seconds by default. It is usually 4 times the hello interval but can be configured manually according to need. 

 

OSPF supports/provides/advantages – 

• Both IPv4 and IPv6 routed protocols 

• Load balancing with equal-cost routes for the same destination 

• VLSM and route summarization 

• Unlimited hop counts 

• Trigger updates for fast convergence 

• A loop-free topology using SPF algorithm 

• Run-on most routers 

• Classless protocol 

 

There are some disadvantages of OSPF like, it requires an extra CPU process to run the SPF algorithm, requiring more RAM to store adjacency topology, and being more complex to set up and hard to troubleshoot.