Cisco 3745

Dec 13 2008   6:27AM GMT

How to configure an interface to default settings in a Cisco Switch or a Cisco Router?

Posted by: Yasir Irfan
Switches, Cisco, Routers, Switching, Routing and Switching, Cisco IOS, Routing, Cisco 2960, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, Cisco 3745, Cisco 3750-E, Router Troubleshooting, Cisco 877W Router, Cisco 6500 Series Catalyst Switch, Cisco 6503, Cisco Catalyst 6503-E Switch, Cisco Catalyst 6506-E Switch, Cisco Catalyst 6509-V-E Switch, Cisco Catalyst 6509-E Switch, Cisco Catalyst 6513 Switch

This is a cool command to erase just the configuration for a particular interface in a Cisco Switch or a Cisco Router.

In the following example we will configure the interface fast Ethernet 0/9  to default configuration

Current Configuration for fast Ethernet 0/9  

ITKE-Cisco#sho running-config interface fastEthernet 0/9

Building configuration…

 

Current configuration : 85 bytes

!

interface FastEthernet0/9

 switchport access vlan 100

 switchport mode access

end

ITKE-Cisco

 

Now we will configure the fast Ethernet 0/9 to default configuration using the following command

“default interface fastEthernet 0/9” 

ITKE-Cisco#configure t

Enter configuration commands, one per line.  End with CNTL/Z.

ITKE-Cisco(config)#default interface fastEthernet 0/9

Interface FastEthernet0/6 set to default configuration

ITKE-Cisco(config)#

 

Running configuration for fast Ethernet 0/9 after configuring to default settings

ITKE-Cisco#sho running-config interface fastEthernet 0/9

Building configuration…

 

Current configuration : 68 bytes

!

interface FastEthernet0/9

 switchport mode dynamic desirable

end

 

ITKE-Cisco#

Dec 2 2008   7:30AM GMT

How to configure SPAN(Switched Port Analyzer ) feature in a Cisco Catalyst Switch

Posted by: Yasir Irfan
Switches, Cisco, Switching, Cisco IOS, Wireshark, Cisco 2960, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, Cisco 3745, Cisco Learning, Cisco 3750-E, Cisco 3560-E, Network Troubleshooting, Show commands, Cisco 6500 Series Catalyst Switch, Cisco 6503, Cisco Catalyst 6503-E Switch, Cisco Catalyst 6506-E Switch, Cisco Catalyst 6509-V-E Switch, Cisco Catalyst 6509-E Switch, Cisco Catalyst 6513 Switch, SPAN, Sniifer

It’s quite important for Network Engineers and an essential network troubleshooting technique to utilize the ability of Cisco Catalyst Switches to mirror the traffic and send it to a sniffer for analysis. All Cisco Catalyst Switches support the Switched Port Analyzer (SPAN) feature. The SPAN copies traffic from the specified interface or VLANs and mirrors this traffic to a specified destination interface (SPAN interface).  Then you can connect the PC with a sniffing tool (Wireshark) installed on the destination SPAN interface to capture all the mirrored traffic.Let’s see how to configure the SPAN in Cisco Catalyst Switches.  To enable the switch SPAN mirroring feature configure the following on the catalyst switch: Configuration Example - Monitoring traffic from a specific interfaceITKEAS01#configure tITKEAS01(config) monitor session 1 source interface gigabitEthernet 0/5

ITKEAS01(config)#monitor session 1 destination interface gigabitEthernet 0/10 

The  above configuration will capture all traffic from interface gigabitEthernet 0/5  and send it to SPAN port interface gigabitEthernet 0/10 

Configuration Example - Monitoring an entire VLAN traffic
ITKEAS01(config)#monitor session 1 source vlan 100
ITKEAS01(config) monitor session 1 destination interface gigabitEthernet 0/10 The  above configuration will capture all traffic of VLAN 100 and send it to SPAN port interface gigabitEthernet 0/10

Use  show monitor session 1 to verify your configuration.

Nov 20 2008   7:54AM GMT

What is Dynamic Host Configuration Protocol (DHCP) Snooping?

Posted by: Yasir Irfan
Network Security, Security, DHCP, Switches, Cisco, Switching, Cisco 2960, Cisco 6500, Cisco Tips, Cisco 3560, Cisco 3745, Cisco Systems, Cisco 6500 Series Catalyst Switch, Cisco 6503, Cisco Catalyst 6503-E Switch, Cisco Catalyst 6506-E Switch, Cisco Catalyst 6509-V-E Switch, Cisco Catalyst 6509-E Switch, Cisco Catalyst 6513 Switch, DHCP Snooping

Dynamic Host Configuration Protocol (DHCP) Snooping is a security feature which filters untrusted DHCP messages, this security feature can protects the devices on the network from associating with an unauthorized DHCP server. When the Dynamic Host Configuration Protocol (DHCP) Snooping feature is enabled on a Cisco Switch , the Cisco Switch builds a table of MAC address, IP address lease time , binding type and interface information. In coming posts I will try to explain to how to enable and configure the Dynamic Host Configuration Protocol (DHCP) snooping security feature in a Cisco Switch.

Oct 12 2008   5:17AM GMT

How to configure SNMPv3 in a Cisco Catalyst Switch – Series 1

Posted by: Yasir Irfan
Security, Switches, Cisco, SNMP, Cisco IOS, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, Cisco 3745, Cisco Learning, Cisco 3560-E, IOS commands, SNMPv3, RFC3410, SNMP Version 3

Configuring SNMP Version 3 in a Cisco Catalyst Switch is bit more complicated compared to SNMP v1 and v2.  But after configuring SNMPv3 you can relax as the SNMPv3 provides more security by adding authentication (username and password) as well as encryption to the protocol.  

What is SNMPv3 ?Simple Network Management Protocol version 3. The specification for this Full Standard protocol is published in RFCs 3410 and 3418. SNMPv3 provides a Full Standard administrative framework (authorization, access control, etc.) and a remote configuration/administration MIB. Also check the SNMPv3 documentation from Cisco Systems. 

How to configure SNMPv3 in a Cisco Catalyst Switch ? 

First we begin with configuration of SNMPv3 on the Cisco Catalyst Switch by creating a SNMP “view”. A “view” defines what information can be accessed by the SNMP user/group when they query the SNMPv3 enabled  Cisco Catalyst Switch.  In the below example we will create “view” called ITKEView. We will enable “system” , “internet” and  “interfaces” SNMP OIDS on the Cisco Catalyst Switch. 

ITKE(config)# snmp-server view ITKEView internet includedITKE(config)# snmp-server view ITKEView system includedITKE(config)# snmp-server view ITKEView interfaces included 

To be continued in next series

Sep 6 2008   10:40AM GMT

The best way to record the serial number for Cisco Devices for Remote support.

Posted by: Yasir Irfan
Switches, Cisco, Telnet, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3745, IOS commands

Imagine if you are accesing the remote router and need to figure out the serial number for a router or the Circuit IDs of the serial interface, then you may start looking your docmented data or call the remote technician to help you out in figuring these details. The best and easy way to get these details in matter of seconds is to put the serial number of each device in the Banner MOTD, and the circuit IDs in the serial interface descriptions.

Sep 3 2008   10:13AM GMT

Enhanced Show interfaces commands in a Cisco Routers & Cisco Catalyst Switches.

Posted by: Yasir Irfan
Switches, Routers, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3745, Show commands, IOS commands

Enhanced Show interfaces commands in a Cisco Routers & Cisco Catalyst Switches.

I was amazed to see many options available with “show interfaces commands which are undocumented, most of these commands are available in IOS release 12.2(44) (may be available with earlier versions, if so do comment).

Some of the undocumented commands are as follows
1) Show interfaces description displays interfaces names, Line and Line protocol status and interface description. Extremely useful to know the status of interfaces which are up or down.
2) Show interfaces counters protocol status displays the L3 protocols active on each interface.
3) Show interfaces summary displays the state of various interface queues and related drop counters in a good tabular format.
4) Show interfaces accounting displays per-protocol in/out counters.

Here are few sample outputs:

Sample Output from Cisco 3745 Router
MBGF-DAC-3745R01#sho interfaces description
Interface                      Status         Protocol Description
Fa0/0                           up             up       WAN connection THru. Bayanat
Fa0/1                            up             up       Connected to LAN
Tu0                                up             up      
MBGF-DAC-3745R01#

Sample output for Cisco 3560 Switch
MBGF-DAC-3560-AS02#sho interfaces description
Interface               Status         Protocol       Description
Vl1                               up             up      
Vl50                            up             up      
Gi0/1                          up             up      
Gi0/2                          up             up      
Gi0/3                          up             up      
Gi0/4                          up             up      
Gi0/5                          up             up      
Gi0/6                          up             up      
Gi0/7                          down           down    
…… 
Gi0/25                         up             up                con2 Khalid
Gi0/26                         down           down    
Gi0/27                         down           down    
Gi0/40                         up             up             CON2-DCAP-50
Gi0/41                         up             up      
Gi0/42                         up             up      
Gi0/43                         up             up  

Gi0/52                         up             up      
MBGF-DAC-3560-AS02#
MBGF-DAC-3745R01#show interfaces counters protocol status
Protocols allocated:
 FastEthernet0/0: Other, IP, DEC MOP, ARP, CDP
 FastEthernet0/1: Other, IP
 Tunnel 0:        Other, IP
 
MBGF-DAC-3560-AS02#sho interfaces counters protocol status
Protocols allocated:
 Vlan1: Other, IP, ARP
 Vlan50: Other, IP, ARP
 GigabitEthernet0/1: Other, IP, Spanning Tree, CDP
 GigabitEthernet0/2: Other, IP, Spanning Tree, CDP
 GigabitEthernet0/3: Other, IP, Spanning Tree, CDP
 GigabitEthernet0/4: Other, IP, Spanning Tree, CDP
 GigabitEthernet0/5: Other, IP, Spanning Tree, CDP
 GigabitEthernet0/6: Other, IP, Spanning Tree, CDP
Allocation failures: 0
MBGF-DAC-3560-AS02#
MBGF-DAC-3745R01#sho interfaces summary

 *: interface is up
 IHQ: pkts in input hold queue     IQD: pkts dropped from input queue
 OHQ: pkts in output hold queue    OQD: pkts dropped from output queue
 RXBS: rx rate (bits/sec)          RXPS: rx rate (pkts/sec)
 TXBS: tx rate (bits/sec)          TXPS: tx rate (pkts/sec)
 TRTL: throttle count

  Interface                    IHQ   IQD  OHQ   OQD  RXBS RXPS  TXBS TXPS TRTL
————————————————————————
* FastEthernet0/0          0     0    0     0 10803000  1233 1511000  873    0
* FastEthernet0/1          0     0    0     0 1379000  876 10614000  1237    0
* Tunnel0                         0     0    0     0 10664000  1233 1414000  873    0
NOTE:No separate counters are maintained for subinterfaces
     Hence Details of subinterface are not shown
MBGF-DAC-3745R01#

MBGF-DAC-3560-AS02#sho interfaces summary

 *: interface is up
 IHQ: pkts in input hold queue     IQD: pkts dropped from input queue
 OHQ: pkts in output hold queue    OQD: pkts dropped from output queue
 RXBS: rx rate (bits/sec)          RXPS: rx rate (pkts/sec)
 TXBS: tx rate (bits/sec)          TXPS: tx rate (pkts/sec)
 TRTL: throttle count

  Interface               IHQ   IQD  OHQ   OQD  RXBS RXPS  TXBS TXPS TRTL
————————————————————————-
* Vlan1                                0     0    0     0     0    0     0    0    0
* Vlan50                             0     0    0     0  1000    2  1000    2    0
* GigabitEthernet0/1       0     0    0 54684     0    0  2000    3    0
* GigabitEthernet0/2       0     0    0 54675     0    0  3000    3    0
* GigabitEthernet0/3       0     0    0 54675     0    0  2000    3    0
* GigabitEthernet0/4       0     0    0 54688     0    0  2000    3    0
* GigabitEthernet0/5       0     0    0 54664     0    0  2000    3    0
* GigabitEthernet0/6       0     0    0 54663     0    0  2000    3    0
………
  GigabitEthernet0/46      0     0    0   274     0    0     0    0    0
* GigabitEthernet0/47      0     0    0  5036     0    0  2000    3    0
* GigabitEthernet0/48      0     0    0 16702     0    0  3000    3    0
* GigabitEthernet0/49      0     0    0     0 10000   18     0    0    0
 * GigabitEthernet0/52      3     0    0     0 389000  208 1652000  223    0
MBGF-DAC-3560-AS02#

MBGF-DAC-3745R01#show interfaces accounting
FastEthernet0/0 WAN connection THru. Bayanat
                Protocol    Pkts In   Chars In   Pkts Out  Chars Out
                   Other          0          0      78271    4696260
                      IP  228129752  604147266  238404086 3496449051
                 DEC MOP          0          0       1304     100408
                     ARP      61201    3672060        230      13800
FastEthernet0/1 Connected to LAN
                Protocol    Pkts In   Chars In   Pkts Out  Chars Out
                   Other      13048    5206152      78271    4696260
                      IP  239500045 3032167184  230865599 2990242469
                 DEC MOP          0          0       1304     100408
                     ARP      97797    5867820      75355    4521300
Tunnel0
                Protocol    Pkts In   Chars In   Pkts Out  Chars Out
                      IP  228294310 1722638248  238403420  156253505
MBGF-DAC-3745R01#

Aug 20 2008   6:22AM GMT

What is Service timestamps logging, and how it can be configured Cisco Switch or a Router?

Posted by: Yasir Irfan
Switches, Cisco, Cisco 2950, Cisco 6500, Cisco 3745, Syslog, IOS commands, Router Troubleshooting, Service timestamp

Logging is a quite essential part of a secure network configuration. Logging not only helps the Network Administrators to identify the issue while troubleshooting, also enables them to react to intrusion attempts or Denial-of –Service attacks.

By default  on Cisco IOS , no timestamp information is included; however, you can enable timestamps and also modify the format of the timestamp attached to SYSLOG message by using the service timestamps log global configuration commands as follows:

ITKE(Config)# service timestamps log {uptime |datetime [msec |localtime |show-timezone]}

I will demonstrate how to configure a Cisco IOS Switch to log the datetime and loclatime.

Before Configuring the service timestamps log you will get the following logs in a IOS Switch.

ITKE#sho log

Syslog logging: enabled (0 messages dropped, 0 messages rate-limited, 0 flushes, 0 overruns, xml disabled, filtering disabled)

No Active Message Discriminator.

No Inactive Message Discriminator.

   Console logging: level debugging, 453895 messages logged, xml disabled,

                     filtering disabled

    Monitor logging: level debugging, 0 messages logged, xml disabled,

                     filtering disabled

    Buffer logging:  level debugging, 453895 messages logged, xml disabled,

                    filtering disabled

    Exception Logging: size (4096 bytes)

    Count and timestamp logging messages: disabled

    File logging: disabled

    Persistent logging: disabled

    Trap logging: level informational, 453898 message lines logged

        Logging to 10.0.0.2  (udp port 514,  audit disabled,

              authentication disabled, encryption disabled, link up),

              453898 message lines logged,

              0 message lines rate-limited,

              0 message lines dropped-by-MD,

              xml disabled, sequence number disabled

              filtering disabled

        Logging to 10.0.0.1  (udp port 514,  audit disabled,

              authentication disabled, encryption disabled, link up),

              453898 message lines logged,

              0 message lines rate-limited,

              0 message lines dropped-by-MD,

              xml disabled, sequence number disabled

              filtering disabled

          Log Buffer (4096 bytes):

17w5d: %LINK-3-UPDOWN: Interface GigabitEthernet0/41, changed state to down

17w5d: %LINK-3-UPDOWN: Interface GigabitEthernet0/41, changed state to up

17w5d: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/41, changed state to up

17w5d: %SEC-6-IPACCESSLOGP: list 102 permitted tcp 10.0.0.6(49336) -> 0.0.0.0(23), 1 packet

Now we will configure the Cisco IOS Switch with the Service timestamp log command with date & local time of the Switch by issuing the following command from the global configuration mode. 

ITKE(config)#service timestamps log datetime localtime

Here are the details of log show in the switch after configuring the service timestamps log command

ITKE#sho log

Syslog logging: enabled (0 messages dropped, 0 messages rate-limited, 0 flushes, 0 overruns, xml disabled, filtering disabled)

No Active Message Discriminator.

No Inactive Message Discriminator.

    Console logging: level debugging, 454006 messages logged, xml disabled,

                     filtering disabled

    Monitor logging: level debugging, 0 messages logged, xml disabled,

                     filtering disabled

    Buffer logging:  level debugging, 454006 messages logged, xml disabled,

                    filtering disabled

    Exception Logging: size (4096 bytes)

    Count and timestamp logging messages: disabled

    File logging: disabled

    Persistent logging: disabled

    Trap logging: level informational, 454009 message lines logged

        Logging to 10.0.0.2  (udp port 514,  audit disabled,

              authentication disabled, encryption disabled, link up),

              454009 message lines logged,

              0 message lines rate-limited,

              0 message lines dropped-by-MD,

              xml disabled, sequence number disabled

              filtering disabled

        Logging to 10.0.0.1  (udp port 514,  audit disabled,

              authentication disabled, encryption disabled, link up),

              454009 message lines logged,

              0 message lines rate-limited,

              0 message lines dropped-by-MD,

              xml disabled, sequence number disabled

              filtering disabled

         

Log Buffer (4096 bytes):

Aug 20 09:10:48: %LINK-3-UPDOWN: Interface GigabitEthernet0/13, changed state to up

Aug 20 09:10:49: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/13, changed state to up

Aug 20 09:10:55: %SYS-5-CONFIG_I: Configured from console by yasir on vty2 (10.0.0.6)

Aug 20 09:11:19: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/13, changed state to down

Aug 20 09:11:20: %LINK-3-UPDOWN: Interface GigabitEthernet0/13, changed state to down

Aug 20 09:11:22: %SEC-6-IPACCESSLOGP: list 102 permitted tcp 10.0.0.1(44420) -> 0.0.0.0(23), 1 packet

Aug 20 09:11:23: %LINK-3-UPDOWN: Interface GigabitEthernet0/13, changed state to up

Aug 20 09:11:24: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/13, changed state to up

Aug 20 09:11:37: %SEC-6-IPACCESSLOGP: list 102 permitted tcp 10.0.0.6(49493) -> 0.0.0.0(23), 1 packet

ITKE#

Aug 2 2008   6:43AM GMT

Show Commands in Cisco Routers and Layer 3 Switches(Most commonly used)Series -1

Posted by: Yasir Irfan
Switches, Cisco, Routers, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, ASA/PIX, Cisco 525, PIX 525, Cisco 3745, Cisco 3750-E, Cisco 3560-E, Show commands, IOS commands, Router Troubleshooting

Some of the widely used commands in Cisco routers are just simple unavoidable, among the most commonly used commands in a Cisco Routers are “show” commands. These commands are essential to Network Administrators. Here is a list of those commands. I will try to cover this in two series. Here is the first series

1. Show running-configuration

The show running-configuration command shows the complete current running configuration in a router, firewall or a switch. Using show running-configuration command a network administrator can troubleshoot almost all issues related routing, filtering secure access, encapsulation, interface mismatch, and many more issues.

2. Show startup-configuration

The show startup-configuration command shows the configuration that is saved on the NVRAM. It is helpful in knowing the configuration that will be applied the next time the routers is reloaded. And also this command is useful in knowing the configuration that was loaded at the start-up of the router before making changes to it.  3. Show Interface

The Show interface command shows the status and statistics of the router interfaces. The show interface command is useful to troubleshoot the routing and link issues. The show interface command output includes interface status, interface IP address and subnet mask, protocol status on an interface, encapsulation type, bandwidth, utilization and much more information related to interface operation.

4. Show ip route

The show ip route command shows the routers routing table.  Routing protocols used and what networks these protocols are advertised. The show ip route command is used to troubleshoot routing problems.

5. Show ip protocols

The show ip protocols displays the routing protocols used in a router and the networks to which these protocols are advertised. It also shows the sources of the routing updates received and very helpful to troubleshoot routing issues.

 

Jul 30 2008   12:59PM GMT

Network Inventory and Configuration Management

Posted by: Yasir Irfan
Networking, Switches, Cisco, Routers, SNMP, Configuration Management, Open Source, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3745, Network Inventory, ZipTie

We all know much about Kiwi Syslog Software.  For many years I am using Kiwi Cat tools for configuration management and automate many of daily tasks. Kiwi Cat tool really helped me to perform many tasks like configuration backup, telnet, SSH and much more. The free version just supports 5 devices; hence I started looking at open source community and came across this wonderful application called Zip Tie.

 What is Zip Tie? ZipTie is a framework for Network Inventory and Configuration Management. ZipTie allows you to easily discover all devices in your network to create a comprehensive inventory and to manage the configuration of those devices. Every installation includes a suite of tools to help manage your network. In addition, ZipTie is constantly under development and leverages a large community of network experts who share their tools, device adapters, and experience. It allows you to create or import your own custom tools or download them from the ZipTie community. The software is free to download, use, and distribute. ZipTie.org is the community site and tools exchange for Open Network Inventory and Configuration Management. (Courtesy Zip tie) For a more detailed explanation of ZipTie, please read this technical white paper by Roger Castillo, AlterPoint’s CTO entitled ZipTie Network Inventory Management Framework - enabling the next era of network management tools.

Screen shot courtesy Zip Tie web site

Jul 17 2008   9:45PM GMT

How to display the configuration of a single interface in Cisco Router or a Switch

Posted by: Yasir Irfan
Networking, Switches, Cisco, Routers, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, Cisco 3745, Cisco Learning, Cisco 3750-E, Cisco 3560-E

Displaying configuration of a single interface can be a time-consuming task if your router or a switch  has extremely long configuration. In this case, the interface keyword of the show running-config command becomes extremely useful.
For example, the show running-config interface serial 0/1  command displays only configuration of the specified interface (without building the whole running configuration)
ITKE#show running-config interface serial 0/1
Building configuration…Current configuration : 124 bytes!
interface Serial0/1
description Connected to ISP
 ip address 192.168.1.6 255.255.255.248