RSSAll Entries in the "LAN/MAN" Category

How to trace physical interface with MAC/IP address in Cisco Devices

In this post I will explain the steps to find the client/end user computer connected physical interface in large Network environment with multiple Access Switches connecting to the core switches or routers. This will help you to trace and troubleshoot devices like a PC or a laptop or other end devices. This is not a difficult task but can certainly be time consuming. You can trace the physical interface by using MAC address or IP address. You can find the MAC address with “sh ip arp” command of particular IP address in gateway router. Let’s start with an IP address. Find out gateway router while checking traceroute to the IP address then login into second hop IP address from end and enter “sh ip arp X.X.X.X” command. C:\>tracert Tracing route to over a maximum of 30 hops 1     1 ms     1 ms     2 ms 2     1 ms    <1 ms    <1 […]

Troubleshoot SFP validation failed on Cisco Nexus 5000

You can follow below steps when you find “SFP validation failed” error for any interface on Cisco Nexus 5000 series switches. Nexus# show interface Eth1/10 Ethernet1/10 is down (SFP validation failed) Hardware: 1000/10000 Ethernet, address: 0014.73b8.ac14 (bia : 0014.73b8.ac14) Description: vmserver1 When interface and transceiver speed is mismatched, the SFP validation failed message is displayed when you enter the show interface ethernet slot/port command. For example, if you insert a 1-Gigabit SFP transceiver into a port without configuring the speed 1000 command on interface, you will get this error. By default, all ports on a Cisco Nexus 5000 Series switch are 10 Gigabits. Troubleshooting steps: You have to change the interface speed from 10G to 1G. For Nexus 5010 only first 8 ports can be downgraded to 1G. Step 1. Set the interface speed to 1000 -> if You are unable to downgrade the speed, Step 2. Unplug the cable […]

How to upgrade\downgrade NX-OS on Cisco Nexus 5000 Switches

The procedure to upgrade/downgrade the NX-OS code on a Nexus 5000 series switches is very easy and it is almost same as for normal IOS. First go to the downloads section on and get the new version of the System software and Kickstart image. A CCO login is required for download NX-OS images. Next access the device, check the available free space in bootflash using dir bootflash: command and delete old NX-OS images if there is no sufficient space in bootflash. Nexus5500# dir bootflash: 744 Apr 20 02:08:48 2011 license_SSI15100AW7_10.lic 49152 Apr 20 02:11:45 2011 lost+found/ 1586 Nov 10 11:47:20 2011 mts.log 25136128 Apr 20 02:01:51 2011 n5000-uk9-kickstart.5.0.3.N1.1b.bin 188700150 Apr 20 02:02:52 2011 n5000-uk9.5.0.3.N1.1b.bin 4096 Jan 01 02:05:55 2009 vdc_2/ 4096 Jan 01 02:05:55 2009 vdc_3/ 4096 Jan 01 02:05:55 2009 vdc_4/ Usage for bootflash:// 331591680 bytes used 1319313408 bytes free 1650905088 bytes total Next upload the new code […]

Difference between Stacking and Clustering on Cisco switches

Stacking Vs Clustering I covered the difference between Stacking and Clustering on Cisco Switches and it also applicable to all other vendor switches.   S.No Stacking Clustering 1 Stacking is a dedicated high performance but interconnecting desktop switches in single wiring closet, single point of authentication and management of desktop switches (single IP address) Clustering is a logical collection of switches independent of hardware interconnect method, single point of authentication and management with no physical boundary. 2 It isolated to the single wiring closet It extends beyond  wiring closet 3 It will not support for the legacy systems. It will support for the legacy systems. 4 It will support limited number of switches for stack It will support 16 switches per cluster 5 No flexibility in stacking design Admin chooses the cluster members. 6 Easily Scalable Not easily scalable as compared to stacking 7 Single IP address for management It […]

Understand HSRP States and HSRP State Transitions

HSRP States  In HSRP process, Router will go through the below states and finally Router will stay in Active or Standby or Listen state. An HSRP router can be in one of six different states. • Initial • Learn • Listen • Speak  • Standby • Active  Initial State This is first and starting state, The initial state indicates that HSRP does not run. This state is entered via a configuration change or when an interface first comes up. Learn State The router is neither in the active or standby state, nor does it have enough information to attempt to claim the active or standby role. Listen State The router knows the virtual IP address of HSRP group, but the router is neither the active router nor the standby router. It listens for hello messages from those routers. Speak State The router sends periodic hello messages and actively participates in […]

What is the difference between HSRP preempt and VRRP preempt

To decide an Active/Master Router, We have to enable preempt, configure priorities and Configure highest IP address on the Routers in the HSRP or VRRP group. In case of VRRP, Router which owns the IP address for the VRRP group is always becomes a Master Router. I thought the only the difference between HSRP and VRRP in case of preempt is Preempt ON by default in VRRP. The Router which is configured with the maximum configurable priority value of 254 in VRRP, that Router would become the master Router. This is not always true. There are some of the rules influence the Master and Preempt in VRRP, Find the difference between HSRP and VRRP in case preempt and Active/Master Router. Difference between HSRP Preempt and VRRP Preempt a)   In VRRP preempt enabled by default, In HSRP Preempt disabled by default. b)   In VRRP, In case priority is equal between Routers, […]