Troubleshooting
Verify the status of Physical and Virtual interfaces.
Command to show IPv4 Interface Brief
S1# show ip interface brief Interface IP-Address OK? Method Status Protocol Vlan99 172.17.99.11 YES manual down down
Command to show IPv6 Interface Brief
S1# show ipv6 interface brief
Vlan99 [down/down]
FE80::C27B:BCFF:FEC4:A9C1
2001:DB8:ACAD:99::1
Auto-MDIX Verification
Command to show MDIX information
S1# show controllers ethernet-controller fa0/1 phy | include MDIX Auto-MDIX : On [AdminState=1 Flags=0x00052248]
Switch Verification Commands
Display interface status and configuration
S1# show interfaces [interface-id]
Display current startup configuration
S1# show startup-config
Display current running configuration
S1# show running-config
Display information about flash file system
S1# show flash
Display system hardware and software status
S1# show version
Display history of commands entered
S1# show history
Display IP information about an interface (IPv4)
S1# show ip interface [interface-id]
Display IP information about an interface (IPv6)
S1# show ipv6 interface [interface-id]
Display the MAC address table
S1# show mac-address-table
Display the MAC address table (alt)
S1# show mac address-table
Verifying the Running Configuration
Command to show Running Config
S1# show running-config Building configuration… Current configuration : 1552 bytes ! interface FastEthernet0/24 switchport access vlan 99 switchport mode access ! (output omitted) ! interface Vlan99 ip address 192.168.99.2 255.255.255.0 ipv6 address 2001:DB8:ACAD:99::1/64 ! ip default-gateway 192.168.99.1
Verifying an Interface
Command to show Interface information
S1# show interfaces fastEthernet 0/1
FastEthernet0/1 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0025.83e6.9092 (bia 0025.83e6.9092)
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
Verifying Routes
Command to verify routes (IPv4)
R1# show ip route
Codes: L - local, C - connected, S - static, 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, E - EGP
i - IS-IS, 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 10.1.1.2 to network 0.0.0.0
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C 10.1.1.0/30 is directly connected, GigabitEthernet0/0
L 10.1.1.1/32 is directly connected, GigabitEthernet0/0
O 10.1.1.4/30 [110/2] via 10.1.1.10, 00:01:18, GigabitEthernet0/2
[110/2] via 192.168.1.3, 00:01:18, GigabitEthernet0/1
C 10.1.1.8/30 is directly connected, GigabitEthernet0/2
L 10.1.1.9/32 is directly connected, GigabitEthernet0/2
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, GigabitEthernet0/1
L 192.168.1.1/32 is directly connected, GigabitEthernet0/1
S* 0.0.0.0/0 [1/0] via 10.1.1.2
Command to verify routes (IPv6)
R1# show ipv6 route
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
U - Per-user Static route, M - MIPv6
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
D - EIGRP, EX - EIGRP external
C 2001:DB8:ACAD:1::/64 [0/0]
via GigabitEthernet0/0/0, directly connected
L 2001:DB8:ACAD:1::1/128 [0/0]
via GigabitEthernet0/0/0, receive
C 2001:DB8:ACAD:2::/64 [0/0]
via Serial0/1/0, directly connected
L 2001:DB8:ACAD:3::1/128 [0/0]
via Serial0/1/0, receive
L FF00::/8 [0/0]
via Null0, receive
R1#
Verifying that a switch supports SSH
Command to verify if a switch supports SSH
S1# show version Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 15.0(2)SE7, RELEASE SOFTWARE (fc1)
To support SSH, a switch must be using a version of the IOS software including cryptographic (encrypted) features and capabilities.
If the IOS image name includes “K9” it means that it supports cryptographic (encrypted) features.
Command to verify if a switch supports SSH (alt)
S1# show ip ssh
You can also use this command to check if a device supports cryptographic features. If the switch is not running a K9 IOS. this command will simply be unrecognized.