HSRP

Sep 5 2009   8:07AM GMT

Review for CCNP BCMSN Official Exam Certification Guide (4th Edition)

Posted by: Yasir Irfan
CCNP, CCNP BCMSN, CCNP Books, Cisco BCMSN (642-812) exam, CCNP BCMSN Official Exam Certification Guide, CCNP Official Certification Library, Cisco Press, Review for CCNP BCMSN Official Exam Certification Guide, Yasir, Boson Exams, HSRP, GLBP, David Hucaby, Router, Supervisor and Power redundancy, Switching, Switches, Router Supervisor and Power redundancy, Cisco Exams, CCNP Preparation

 

Hi folks, as I received a CCNP Official Certification Library, fifth edition thanks to Cisco Press (Jamie) for the great support lending on me all the time. To brief about the CCNP Official Certification Library, fifth edition is a comprehensive package for the four Cisco CCNP exams BCMSN, BSCI, ISCW and ONT. Starting from this post I will try my best review all the four Certification books comes with the CCNP Official Certification Library, fifth edition thanks. To start with I will go with the CCNP BCMSN Official Exam Certification Guide, fourth edition.

The CCNP BCMSN Official Exam Certification Guide, fourth edition is a true guide for preparing for the Cisco BCMSN (642-812) exam. The author David Hucaby did a wonderful job by the explaining the material in short concise way that facilitates easy learning.

The CCNP BCMSN Official Exam Certification Guide, fourth edition is divided into six parts , each part is well written and  more over its easy to understand. The most liked chapter for me is the Router, Supervisor and Power redundancy. Thanks to David Hucaby, I was able to migrate our network from HSRP to GBLP succefully. He explained the concept very well like I said it’s really easy to understand.

The CCNP BCMSN Official Exam Certification Guide, fourth edition does have the Scenarios for final preparations  There are nine scenarios covering wide range of concepts and are helpful not only from the exam point of view but also it can be used to troubleshoot the problems in real networks faced by some folks.

One more amazing thing I liked in the CCNP BCMSN Official Exam Certification Guide, fourth edition is the practice exams which are handful for the folks who has little exposure to real world networks, but it’s always recommend to have some hands on experience with Switches configuration and analysis.

Overall an excellent guide which can leads you to taste the success of passing Cisco BCMSN (642-812) exam. I would rate this guide 4.5 out of 5.

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 12 2008   12:56PM GMT

Solution for %IP-4-DUPADDR: Duplicate address error log in your Cisco 6500 Switches running HSRP

Posted by: Yasir Irfan
Switches, Cisco, Switching, Routing and Switching, Cisco IOS, WebEx, Hot Standby Router Protocol, HSRP, Cisco 6500, Cisco Tips, Cisco Learning, Network Troubleshooting, Cisco Systems, Cisco 6500 Series Catalyst Switch, Cisco Catalyst 6513 Switch, Cisco Support, TAC

Dear Friends In my previous post I was talking about the HSRP error generated in Cisco 6513 Switches with a Duplicate IP Address. I did open a TAC case with Cisco Systems. I should first of all salute Cisco for the great support to solve this issue.  Cisco TAC Engineer Mr. Pradeep was in constant touch with me in this case to resolve the issue. The best part of their support is the use of technology. Mr. Pradeep initiated a Web Ex meeting with me and spent more than hour to check step by step.  He helped me a lot and did learned lot of things from Cisco TAC team, like how to approach the problem and what measures should be taken to trouble shoot any problem. Finally we came to the conclusion there are no bugs or errors in the IOS we are using. There are no problems either in hardware or in the current configuration.I would like to quote the solution provided Mr. Pradeep TAC Engineer, Cisco Systems “Let me summarize this issue. You told me that there is one Trojan affected PC/ Host, which is connected to your access switch. Further, you got some duplicate IP address messages on your core switch. During troubleshooting, I have checked and verified that the Cisco’s Switches are working fine. Their configurations were correct. Generally duplicate IP addresses can be impounded by “broken HSRP links” or “incorrect DHCP pool configuration”, or by misconfiguration of switches or STP. I found that this entire setup is configured correctly. Furthermore, I would like to inform you that Cisco’s IOS cannot resolve Trojan issue on any PC. PC has got its own Operating System, and IOS can work only and only on “Cisco’s device”

 So now it’s quite clear if you face this kind of problem make sure the infected PC is removed from the network and make sure it s free from any sort of Trojans or Virus.

Nov 9 2008   6:51AM GMT

Don’t panic whenever you see %IP-4-DUPADDR: Duplicate address error log in your Cisco 6500 Switches running HSRP

Posted by: Yasir Irfan
Networking, Switches, Cisco, Switching, Routing and Switching, Hot Standby Router Protocol, HSRP, Cisco 6500, Cisco Tips, Network Troubleshooting, Trojan, 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

If you are running HSRP and one of your VLAN is down and the following errors are generated in your Switch don’t panic. All this happens due the Trojans in the network.

MBGF-DAC-6500-BB01#sho log

Nov  9 07:54:21: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:54:52: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:55:22: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:55:52: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:56:11: %SEC-6-IPACCESSLOGS: list 12 permitted 10.0.0.1 256 packets

Nov  9 07:56:22: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:56:52: %IP-4-DUPADDR: Duplicate address 10.12.0.1 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:57:11: %SEC-6-IPACCESSLOGS: list 12 permitted 10.0.0.2 263 packets

Nov  9 07:57:11: %SEC-6-IPACCESSLOGS: list 12 permitted 10.0.0.7 200 packets

Nov  9 07:57:22: %IP-4-DUPADDR: Duplicate address 10.12.0.1 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:57:52: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

MBGF-DAC-6500-BB01#

Last week at 3 A.M I received a call from our Help Desk, stating our applications are not running in one our departments. I logged remotely to our Network and try figured out what is problem. Upon carefully looking at the logs in our Cisco 6513 core Switches I figured out a duplicate IP address is created which happens to be the Standby IP address for the Core Switch for HSRP.

I figured out the PC by looking the at mac address generated in the log and closed the network connection for that particular PC and the problem was solved.

If you face similar problems its better to change the HSRP Standby IP address in Core Switches and then try figure out the infected PC. Once the PC is figured out close the network connection and make sure the Trojans are removed. Upon cleaning the infected PC you can reconfigure the HSRP Standby IP address to the previous one.

Once I get the complete solution to fix this problem I will post it.

Jun 17 2008   7:02AM GMT

Configuring HSRP in Cisco 6500 Switch

Posted by: Yasir Irfan
Networking, Switches, HSRP, Cisco 6500

Configuring HSRP in a Cisco 6500 Switch

Yasir
Personel Website:www.yasirirfan.com