Network technologies and trends

December 30, 2010  8:35 PM

What are key features and benefits NX-OS offers Series 1

Yasir Irfan Yasir Irfan Profile: Yasir Irfan

Apparently the NX-OS includes some quite interesting kef features and benefit. In this post I will try to highlight few of those features. Some of them are as follows

  • Virtual device contexts (VDC): Cisco Nexus 7000 Series switches can be segmented into virtual devices based on customer requirements. VDCs offer several benefits such as fault isolation, administration plane, separation of data traffic, and enhanced security.
  • Virtual Port Channels (vPC): Enables a server or switch to use an EtherChannel across two upstream switches without an STP-blocked port to enable use of all available uplink bandwidth.
  • Continuous system operation: Maintenance, upgrades, and software certification can be performed without service interruptions due to the modular nature of NX-OS and features such as In-Service Software Upgrade (ISSU) and the capability for processes to restart dynamically.
  • Security: Cisco NX-OS provides outstanding data confidentiality and integrity, supporting standard IEEE 802.1AE link-layer cryptography with 128-bit Advanced Encryption Standard (AES) cryptography. In addition to CTS, there are many additional security features such as access control lists (ACL) and port-security, for example.

December 30, 2010  8:31 PM

A brief overview of Cisco NX-OS

Yasir Irfan Yasir Irfan Profile: Yasir Irfan

No doubt Cisco Nexus 7000 Series switch is a better choose for Data Center so does the NX-OS. Cisco Systems built the NX-OS data center-class operating system with modularity, resiliency and serviceability as it foundation. Cisco Systems designed NX-OS based on Cisco Storage Area Network Operating System (SAN-OS) software. Some of the advantages of Cisco NX-OS are as following

  • Unified data center operating system
  • Robust and rich feature set with a variety of Cisco innovations
  • Flexibility and scalability
  • Modularity
  • Virtualization
  • Resiliency
  • IPv4 and IPv6 IP routing and multicast features
  • Comprehensive security, availability, serviceability, and management features

December 30, 2010  1:21 PM

Skype outage was caused by a bug in its client

Yasir Irfan Yasir Irfan Profile: Yasir Irfan

In his blog post Lars Rabbe , Skype’s chief Information officer revealed that the recent Skype outage was caused by the peer-to-peer (P2P) network becoming unstable and suffering a critical failure.

The failure lasted approximately 24 hours from December 22, 0800 PST/1600 GMT to December 23, 0800 PST/1600 GMT.

According to Lars their support servers responsible for offline instant messaging became overloaded. Which resulted in delayed responses to some of Skype clients. The Skype for Windows client (version 5.0.0152) crashed dye to delayed responses from overloaded severs.

His detailed explanation can be accessed from his blog post.

December 30, 2010  1:06 PM

According to Shaw Wu,BlackBerry PlayBook launch may delay due to battery issues

Yasir Irfan Yasir Irfan Profile: Yasir Irfan

According to Kaufman Brothers analyst Shaw Wu, BlackBerry’s answer to iPad and Samsung Galaxy Tab, BlackBerry Playbook needs a re-engineering to improve its battery life. The Playbook is due to be released in 2011.

“Wu claims he is hearing that the PlayBook “needs to improve its relatively poor battery life of a few hours compared to 6 hours for the Samsung Galaxy Tab and 10 hours for [Apple’s] iPad.” As a result, Wu writes, the launch of the BlackBerry PlayBook may be delayed until May, 2011. Wu notes that the cause of the battery issues may stem from the fact that QNX, the PlayBook’s operating system, was designed for use in scenarios where battery life is not an issue — such as in automobiles.”

Wu has also raised concerns over app store monetization. Apple is the only store where developers can count on revenue, while Android “suffers from piracy and inconsistency”.

Wu has estimated that RIM will ship around 700,000 PlayBooks next year, while other analysts have predicted up to one million shipments.

RIM has announced that the PlayBook measures 5.1 inches by 7.6 inches by 0.4 inches and weighs 0.9 pounds. The PalyBook has a 1024-by-600 multitouch capacitive display, designed around a dual-core, 1-GHz Cortex A9 microprocessor with one gigabyte of RAM.

The tablet will run QNX’s mobile operating system, as well as HTML5 and Flash 10.1, with native hardware support to accelerate apps further.

December 29, 2010  5:27 AM

How to allocate physical interfaces to VDC in a Cisco Nexus 7000 Series switch?

Yasir Irfan Yasir Irfan Profile: Yasir Irfan


To allocate physical interfaces to VDC from the config terminal mode type the VDC name and then allocate the physical interfaces as shown below by using the command “allocate interface”

N7000-ITKE01#configure t

N7000-ITKE01 (config)#vdc VDC-CORE1

N7000-ITKE01-DC-CORE1 (config-vdc)#allocate interface  Ethernet1/1

N7000-ITKE01-DC-CORE1 (config-vdc)#allocate interface  Ethernet1/2

N7000-ITKE01 -DC-CORE1 (config-vdc)#allocate interface  Ethernet1/3

Now let’s verify the Interface allocation to the VDC by using following command ” show vdc membership”

N7000-ITKE01-DC-CORE1# show vdc membership

vdc_id:2 vdc_name: DC-CORE1 interfaces:
        Ethernet1/1           Ethernet1/2           Ethernet1/3          
        Ethernet1/4           Ethernet1/5           Ethernet1/6          
        Ethernet1/7           Ethernet1/8           Ethernet1/9          
        Ethernet1/10          Ethernet1/11          Ethernet1/12         
        Ethernet1/13          Ethernet1/14          Ethernet1/15         
        Ethernet1/16          Ethernet1/17          Ethernet1/18         
        Ethernet1/19          Ethernet1/20          Ethernet1/21         
        Ethernet1/22          Ethernet1/23          Ethernet1/24         
        Ethernet1/25          Ethernet1/27          Ethernet1/29         


In addition to interfaces other physical resources such as IPv4 router memory, IPv6 router memory, port-channels, SPAN sessions can be allocated to individual VDC.

December 28, 2010  5:44 AM

How to configure VDC in Cisco Nexus 7000 Series switch?

Yasir Irfan Yasir Irfan Profile: Yasir Irfan

In my previous post we came to know briefly about Virtual Device Contexts (VDC) and what are the advantages of Virtual Device Contexts (VDC) as well.

Configuring Virtual Device Contexts (VDC)   Cisco Nexus 7000 Series switch is as simple as just entering the VDC name, by following below mentioned steps we can create VDC named VDC-Admin

Step 1

Connect to Cisco Nexus 7000 Series switch using a console port.

Step 2

Create a VDC named DC-CORE1

N7000-ITKE01#configure t

N7000-ITKE01 (config)#vdc  DC-CORE1

Step 3

Verify the created VDC by using following commands “Show vdc” and “show vdc VDC-CORE1 detail” as demonstrated below.

N7000-ITKE01# sho vdc

vdc_id  vdc_name                          state               mac            
——  ——–                          —–               ———-     
1       VDC-Admin                         active              00:26:98:07:1c:c1
2       DC-CORE1                          active              00:26:98:07:1c:c2
3       DC-AGG1                           active              00:26:98:07:1c:c3


The show VDC command shows VDC id based on which VDC created first.BY default VDC id is assigned to the default VDC. In this case it is VDC-Admin.

VDC-Admin# sho vdc DC-CORE1 ?
  >           Redirect it to a file
  >>          Redirect it to a file in append mode
  detail      Show detailed vdc information
  membership  Show vdc interface membership information
  resource    Show resource configuration for VDC
  |           Pipe command output to filter

N7000-ITKE01# sho vdc DC-CORE1 detail

vdc id: 2

vdc name: DC-CORE1
vdc state: active
vdc mac address: 00:26:98:07:1c:c2
vdc ha policy: RESTART
vdc dual-sup ha policy: SWITCHOVER
vdc boot Order: 1
vdc create time: Wed Dec 28 08:44:51 2010
vdc reload count: 0
vdc restart count: 0






In upcoming post I will show how to allocate physical interfaces to the newly created VDC.

December 27, 2010  6:22 AM

What is Virtual Device Contexts (VDC) in Nexus 7000 Series Switches?

Yasir Irfan Yasir Irfan Profile: Yasir Irfan


The Virtual Device Contexts (VDC) is a new feature introduced in Cisco Nexus 7000 NX-OS, so does it happens to be the first Data Center Switch to provide Virtual Device Contexts (VDC) capabilities. The Virtual Device Contexts (VDC) allows a Cisco Nexus 7000 Series switch to be logically segmented into four different virtual switches (device contexts). The logical separation of single Nexus 7000 into multiple logical devices provides the following benefits:

  • Administration and management separation
  • Change and failure domain isolation from other VDSs
  • Address, VLAN, VRP and vPC isolation.

When the Cisco Nexus 7000 Series switch is first booted, all interfaces of all line cards in the modular switch platform are placed in the default VDC (VDC 1).  Up to four VDCs can be created including the default VDC, but an interface can only belong to one VDC.  Interfaces from different line cards can be placed in different VDCs.  Once an interface is placed into a VDC, the interface can no longer be managed in the default VDC context.

The Cisco Nexus 7000 Series switch shares some components between VDC(s), which include the following:

  • A single instance of the kernel which support all of the processes and VDCs.
  • Supervisor Modules
  • Fabric Modules
  • Power Supplies
  • Fan trays
  • System fan trays
  • CMP
  • CoPP
  • Hardware SPAN resources.

December 26, 2010  5:46 AM

What happened to Ten Giga Ethernet interface in Nexus 7000 Series Switch?

Yasir Irfan Yasir Irfan Profile: Yasir Irfan

 Our Network Infrastructure is currently being under major revamp. We are expanding our Data Center as well our enhancing our services to our customers with the introduction of IP telephony, better internet speed and of course better systems.

When we started planning for this project lot of solutions were presented, starting from Nortel, Juniper and Cisco. We opted for the Cisco recommended solution. In the new solution we are having Cisco Nexus 7010 as our Core Switches.

Since still we are staging our Cisco Nexus 7010 switches, while doing so I figure out there are no more Giga Ethernet or Ten Giga Ethernet interfaces in the Cisco Nexus 7010 Series Switch. All interfaces are known as Ethernet ports.

VDC-Admin-DC-ITKE1(config)# interface ?

  ethernet      Ethernet IEEE 802.3z

  loopback      Loopback interface

  mgmt          Management interface

  port-channel  Port Channel interface

  vlan          Vlan interface

VDC-Admin-DC-ITKE1 (config)# interface ethernet 1/26

VDC-Admin-DC-ITKE1 (config-if)# speed ?

  10     10Mb/s

  100    100Mb/s

  1000   1Gb/s

  10000  10Gb/s

  auto   Auto negotiate speed


VDC-Admin-DC-ITKE1 (config-if)#

 But nothing to worry they will not just support 10Mb/s but even they can support 10 GB/s. This is one of key difference I found between Cisco Catalyst 6500 Series and Nexus 7000 Series Switches. As we proceed further I let you all know the major differences between Cisco Catalyst 6500 Series and Nexus 7000 Series Switches. One fact to known about Nexus 7000 Series Switches run by Cisco NX-OS software. It was specifically designed for the most mission-critical place in the network, the data center.

December 21, 2010  5:29 AM

What is GLBP and how it can be configured in Cisco Devices? – Series 2

Yasir Irfan Yasir Irfan Profile: Yasir Irfan


In my previous post I was discussing about Gateway Load Balancing Protocol (GLBP), now let’s see how Gateway Load Balancing Protocol (GLBP) does load balancing?  Basically there are three different types of Load balancing algorithms applied

Round Robin:

  • This method is the default method used by Gateway Load Balancing Protocol (GLBP).
  • In this method the when the client sends ARP requests to resolve the MAC- address of the default gateway , the reply contains the MAC address of the next possible router in round-robin fashion


  •  Gateway Load Balancing Protocol (GLBP) places a weight on each device to calculate the amount of load sharing that will occur through MAC assignment
  • The routers participating in GLBP will advertise its weight and AVG will act based on that value
  • For example if we have two routers named ITKE-Router A and ITKE-Router B. If the ITKE-Router A has double the bandwidth capacity then the ITKE-Router B. ITKE-Router A will be configured with the double weighting value of ITKE-Router B


  • Each Client will always get the same Virtual MAC address.
  • The Mac-address of the host is used to determine which AVF’s mac the host is directed towards.
  • This method is used when the client needs a consistent gateway MAC -address.
  • Host dependent GLBP is not recommended in situation where there are small number of hosts, for example, less than 20

In upcoming posts let’s see how to configure Gateway Load Balancing Protocol (GLBP) in Cisco devices.

December 8, 2010  7:59 AM

What is GLBP and how it can be configured in Cisco Devices? – Series 1

Yasir Irfan Yasir Irfan Profile: Yasir Irfan


GLBP better known as Gateway Load Balancing Protocol (GBLP) is a Cisco proprietary protocol especially designed overcome the limitations of Hot Standby Routing Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP). The added feature to Gateway Load Balancing Protocol (GLBP) is it can load balance between the gateways where as in HSRP and VRRP, the standby routers are configured for redundancy and act as standby only and become active only when the active router fails.

The Gateway Load Balancing Protocol (GLBP) provides load balancing over multiple routers (gateways) using a single virtual IP address and multiple virtual MAC addresses. The forwarding load is shared among all routers in a GLBP group rather than being handled by a single router while the other routers stand idle. Each host is configured with the same virtual IP address, and all routers in the virtual router group participate in forwarding packets. GLBP members communicate between each other through hello messages sent every 3 seconds to the multicast address, User Datagram Protocol (UDP) port 3222 (source and destination).

The Gateway Load Balancing Protocol (GLBP) elects one router as active virtual gateway (AVG) based on highest priority value or highest IP address in the group, if there is no highest priority.  The active virtual gateway (AVG) to respond to ARP requests sent to the virtual gateway IP address replying different virtual MAC addresses depends on which load-balancing algorithm is configured.

All routers participating in GLBP group gets the necessary virtual MAC addresses from the active virtual gateway (AVG). Up to four virtual MAC addresses can be used in any group. Each of these routers is referred to as an active virtual forwarder (AVF), forwarding traffic received on its virtual MAC address. Other routers in the group serve as backup or secondary virtual forwarders, in case the AVF fails. The AVG also assigns secondary roles.

The Gateway Load Balancing Protocol (GLBP) is part of CCNP 642-813 Exam curriculum and you must master this protocol as you can expect few questions.

In upcoming posts I will try to highlight on load balancing techniques used and how to configure Gateway Load Balancing Protocol (GLBP) in Cisco Routers and Cisco Catalyst Switches .When it comes to Catalyst Switches GLBP is currently available with Catalyst 6500 Supervisor 2 with IOS Release 12.2(14) SY4 or later and Supervisor 720 with IOS Release 12.2(17a) SX4 switch platforms.

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