Cisco 2950

Dec 27 2008   6:19AM GMT

Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 3

Posted by: Yasir Irfan
Networking, Switches, Cisco, IEEE, Switching, Cisco IOS, Cisco 2960, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, Cisco Learning, Cisco 3750-E, Cisco Systems, Etherchannel, Cisco 6500 Series Catalyst Switch, 802.3ad, Etherchannel configuration, Etherchannel restrictions, Protocol, PAGP, LACP, Port Aggregation Protocol, Link Aggregation Control Protocol

Dear Friends, hope everyone is having great holidays, have fun. In my previous post  I was focusing on some of the limitations of Etherchannel. Now let’s proceed a step ahead and figure out about the Etherchannel negotiation protocols. Etherchannels can be negotiated between two Cisco Catalyst Switches  to provide some dynamic link configuration.

 Basically there are two types of protocols are available, which can be used to bundled the automated creation of an Etherchannel in the Cisco Catalyst Switches.

In upcomming post I will try to concentrate on automating the creation of an Etherchannel . Have fun and happy new year 2009.

Dec 20 2008   6:33AM GMT

Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 2

Posted by: Yasir Irfan
Networking, Switches, Cisco, Switching, Routing and Switching, Cisco 2960, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, Cisco 3750-E, Cisco Systems, Etherchannel, Layer 2 Etherchannel, Layer 3 Etherchannel, Etherchannel configuration, Etherchannel restrictions

Dear Friends, in my previous post I just introduced Etherchannel, now let’s proceed one step ahead,  there are certain limits with the Etherchannel  lets figure out what are those  limits,

 

·         An Etherchannel  Group Number must be in the range of 1 to 256.

·         All ports in the target Etherchannel  group MUST be in the same VLAN.

·         If one physical link in the Etherchannel  group is a TRUNK, then all other ports must be configured as trunks carrying the same VLAN information.

·         Any defined broadcast limits must be the same across all ports in an Etherchannel.

·         An LACP Etherchannel  group cannot support any physical links in half duplex mode.

·         No port in the Etherchannel  group can be defined as a SPAN port.

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 22 2008   12:56PM GMT

How to configure DHCP Snooping in a Cisco Catalyst Switches.

Posted by: Yasir Irfan
Networking, DHCP, Switches, Cisco, Switching, Routing and Switching, CCNP, Cisco IOS, Cisco 2960, Cisco 2950, HSRP, Cisco 6500, Cisco Tips, Cisco 3560, Cisco Learning, Server Security, Cisco 3750-E, Cisco 3560-E, IOS commands, 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, Configuring DHCP Snooping, 802.1 Q, Trunk Ports

 So here we go, with the configuration of DHCP snooping on a Cisco Switch. This feature protects the network by allowing the Cisco Switches to accept DHCP response message only from the authorized servers connected to the trusted interfaces in a Cisco Switch.

All Switch to  Switch connections are configured as 802.1 1Q Trunk ports.

IP Address and HSRP Details for the Core Switches  From the above scenario we have two Cisco 6513 Series Switches as a Core/ Distribution with three VLANS one for management of Switches VLAN 50,VLAN 100 for all the servers and VLAN 101 for clients. Two Cisco 3560 Series Switches as Server Farm Switches and a Cisco 3560 Series Switch as an Access Switch.There are two DHCP servers with an IP address 10.0.1.100 and 10.0.1.101 connected with Server Farm Switches with HP NIC teaming. We configure DHCP Snooping based on above scenario. 

The first step to configure DHCP Snooping is to turn on DHCP snooping in all Cisco Switches using the “ip dhcp snooping” command. 

All Cisco Switches (config)#ip dhcp snooping  Second step is to configure the trusted interfaces, from the above scenario all trunk ports are configured as trusted ports as well as the interfaces G0/7,(ITKESF01 50.0.0.6),  G0/17,(ITKESF02 50.0.0.7),  G0/9 ITKESF01 50.0.0.6)  and G0/18 ITKESF02 50.0.0.7)  connected to DHCP servers with IP 10.0.1.100 and 10.0.1.101. Lets configure all trunk ports in ITKEBB01 

ITKEBB01(config)#interface range  gigabitEthernet 3/21 - 23

ITKEBB01 (config-if)#ip dhcp snooping trust 

Now let’s configure all trunk ports in ITKEBB02 

ITKEBB02(config)#interface range  gigabitEthernet 3/21 - 23 ITKEBB02 (config-if)#ip dhcp snooping trust 

ITKEBB02 (config)#interface gigabitEthernet 3/16

ITKEBB02 (config-if)#ip dhcp snooping trust 

Now let’s configure the trusted ports for the DHCP servers  

ITKESF01(config)#interface gigabitEthernet 0/7

ITKESF01 (config-if)#ip dhcp snooping trust 

ITKESF01(config)#interface gigabitEthernet 0/17 ITKESF01 (config-if)#ip dhcp snooping trust 

ITKESF02(config)#interface gigabitEthernet 0/9

ITKESF02 (config-if)#ip dhcp snooping trust 

ITKESF02(config)#interface gigabitEthernet 0/18 ITKESF02 (config-if)#ip dhcp snooping trust 

Now let’s configure the trunk ports  Access Switch ITKEAS01 

ITKEAS01(config)#interface range  gigabitEthernet 0/49 - 52

ITKEAS01 (config-if)#ip dhcp snooping trust 

Finally we are going to configure VLANS for DHCP snooping DHCP snooping will used on all the VLANs (VLAN 100 & 101)except management VLAN 50 . Also we will limit the requests rate received in the Access Switch (ITKEAS01)  ALL SWITCHES(config)# ip dhcp snooping VLAN 100,101 

ITKEAS01(config)#interface range  gigabitEthernet 0/1 - 48

ITKEAS01 (config-if)#ip dhcp snooping limit rate 20

Displaying the DHCP snooping  

For further reference please do check this article from Cisco about DHCP snooping.

Nov 22 2008   7:22AM GMT

Why should we consider implementing DHCP Snooping?

Posted by: Yasir Irfan
Networking, Security, DHCP, Switches, Cisco, Switching, Cisco 2960, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, Cisco 3750-E, Cisco 3560-E, Err-disable, Cisco Systems, Cisco 6500 Series Catalyst Switch, Cisco 6503, DHCP Snooping

Dear FriendsIn my previous post I was discussing about the DHCP Snooping, it may be hard to believe a DHCP sever can lead to lot troubles in your network. Consider a host sends out DHCP discovery packets, it listens for a DHCP offers packets and accepts the first available offer from a DHCP server. Guess what happens if the host gets a DHCP offer from a rouge DHCP server? The host could end up with using rouge DHCP server with an IP address and the default gateway. The host cannot access any of the resources from your network. 

Yes we can prevent this with DHCP snooping thanks to Cisco. DHCP snooping classifies interfaces as either trusted or untrusted. DHCP messages received on trusted interfaces will be permitted to pass through the Cisco switch, but DHCP messages received on untrusted interface in a Cisco Switch results in putting the interface into error disable state. Configuring DHCP snooping in a Network is quite troublesome job but I will try to make things easier for you by using a scenario, which hopefully I am going post soon.

Oct 20 2008   5:06AM GMT

How to configure SNMPv3 in a Cisco Catalyst Switch – Series 2

Posted by: Yasir Irfan
Switches, Cisco, SNMP, Cisco IOS, Cisco 2960, Cisco 2950, Cisco 6500, Cisco Tips, Cisco 3560, Cisco Learning, SNMPv3, Cisco Systems

In the first series we just started to know about SNMP Version 3 and we just created a SNMP View called ITKEView. Now let’s proceed further and create a SNMP group called “ITKEGroup”. This group is granted an access to view “ITKEview” which we created in the previous step. 

ITKE(config)# snmp-server group ITKEview v3 auth

Finally let’s create a SNMP username called   “ITKEuser” and grant it an access to the “ITKEGroup” that we created in previous step. We will provide an authentication password as well as privacy password which will serve as an encryption key for the SNMP protocol. ITKE(config)# nmp-server user ITKEuser  ITKEGroup  v3 auth md5 ITKEpass priv des56 ITKEpass2

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 8 2008   8:12AM GMT

How to reset/delete the password & configuraton on a Cisco WS-C350-48-SMI

Posted by: Yasir Irfan
Switches, Cisco, Cisco 2950, HyperTerminal, Cisco Tips, Cisco 3560, Cisco 3750-E, Cisco 3560-E, IOS commands, Password reset

This article describes the procedure for resetting / delete  the  password & current configuration on a Cisco Catalyst WS-C3550-48-SMI.Model: WS-C3550-48-SMI
Warning: This procedure will remove the switch configuration. Be sure to have a backup of you current switch configuration before proceeding.The Cisco WS-C3550-48-SMI Catalyst switch is similar to most Catalyst switches and the procedure for resetting the password is the same.

Step 1: Connect the console cable to the switch and start your terminal program (HyperTerminal/Secure CRT). Console port settings are 9600,8,N,1

Step 2: Hold the MODE button (on the front of the switch) while you power on the switch.

Step 3: Hold the MODE button for a few seconds until you the System light stop flashing.Step 4: At this point, the switch should be in ROMmon mode. Step 5: From ROMmon mode, type: flash_initStep 6: From ROMmon mode, type: delete flash:config.textStep 7: From ROMmon mode, type: boot

At this point the switch will boot as normal with a new configuration and no password.

 

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.