Saturday, September 17, 2011
Wednesday, September 7, 2011
My TSHOOT Exam!
I was surprised by the format.. I expected the format to be like the ROUTE and SWITCH exam with good proportion of all types of question. But when the exam started the exam instruction said that there will be 4 questions and pass marks is 790! I read it twice and clicked next. The first 3 questions were multiple choice questions and the fourth one was a topology based question with 14 trouble tickets in it. The exam was brilliant. It was so much fun solving those trouble tickets. Absolutely scary too because I was running out of time. But it was great experience. The TSHOOT exam rocks..
Tuesday, September 6, 2011
CCNP Accomplished!!
Everyone, I finished my CCNP TSHOOT exam today and with it I have I have finished all 3 exams for CCNP! I will get my certification kit soon. Can't stop laying hands on it. Will update a blog soon about the TSHOOT exam. It was the best exam I ever took!
Tuesday, August 9, 2011
Things that you might miss when studying HSRP
- HSRP group can contain more than two members; One is active member, one is standby router and the others will be in listening HSRP state.
- HSRP sends hello messages to 224.0.0.2 (All Routers Multicast Address) using UDP port 1985.
- HSRP group numbers can be [0,255]
- HSRP groups are locally significant on the interface. This is very important point to understand. For example, HSRP group 1 on the VLAN 10 interface is not same as the HSRP group 20 on VLAN 11 interface.
- HSRP router election:
Active Router is the one with the highest priority
If there is a priority tie then the router with the highest HSRP Ip address wins.
6. HSRP States: Disabled> Init> Listen> Speak> Standby> Active.
7. Only standby member monitors the hello messages. Listening members do not monitor them.
8. Default hello message every =3s; Hold time=10s
9. The actual interface address and the standby address must be configured to be in the same IP subnet.
9. The actual interface address and the standby address must be configured to be in the same IP subnet.
Sunday, July 17, 2011
Understanding your NetFlow
I was using SevOne at office the other day to pull some reports of the nonunicast traffic in a vlan to troubleshoot a particular GLBP issue. And then I wondered what will I do without such tools. Then I became curious and wanted to know how it actually knows all that information.
SevOne consolidates granular performance data from various data sources such as SNMP, NetFlow, VoIP, IP SLA, NBAR and WMI onto a unified dashboard. I want to particularly focus on NetFlow in this paticular article.
Netflow is a network protocol that was developed by Cisco in 1996. It was designed to collect IP traffic information. Soon it became an industry standard for traffic monitoring. There has been several versions of Netflow developed over the years and its current state is known in the industry as Flexible NetFlow.
The flow is defined by factors such as Source IP address, Destination IP address, Source port, Destination Port, Layer 3 protocol type. The version5 which is the most common version in use has 18 such fields. Version 5 is great if you are just looking for regular IPv4 traffic. It does not provide in depth analysis of the traffic but provides a very good overview of the composition of your traffic flow. The Later versions such as v7 and v8 were extensions of v5 and had features like router-based aggregation and reduced NetFlow export data volume.
The problem with these versions was that they used fixed export formats that were not flexible and adaptable. This caused the customers to re-engineer for each new version. So they built a more flexible and extensible export format called version 9. This was done by introducing the notion of template. Templates provide an extensible design to the record format, a feature that should allow future enhancements to NetFlow services without requiring concurrent changes to the basic flow-record format. This new feature supports additional technologies such as MPLS or Multicast.
We also have Internet Protocol Flow Information Export (IPFIX) coming up in the near future which is based on NetFlow Version 9 but acts as a more universal industry standard.
SevOne consolidates granular performance data from various data sources such as SNMP, NetFlow, VoIP, IP SLA, NBAR and WMI onto a unified dashboard. I want to particularly focus on NetFlow in this paticular article.
Netflow is a network protocol that was developed by Cisco in 1996. It was designed to collect IP traffic information. Soon it became an industry standard for traffic monitoring. There has been several versions of Netflow developed over the years and its current state is known in the industry as Flexible NetFlow.
The flow is defined by factors such as Source IP address, Destination IP address, Source port, Destination Port, Layer 3 protocol type. The version5 which is the most common version in use has 18 such fields. Version 5 is great if you are just looking for regular IPv4 traffic. It does not provide in depth analysis of the traffic but provides a very good overview of the composition of your traffic flow. The Later versions such as v7 and v8 were extensions of v5 and had features like router-based aggregation and reduced NetFlow export data volume.
The problem with these versions was that they used fixed export formats that were not flexible and adaptable. This caused the customers to re-engineer for each new version. So they built a more flexible and extensible export format called version 9. This was done by introducing the notion of template. Templates provide an extensible design to the record format, a feature that should allow future enhancements to NetFlow services without requiring concurrent changes to the basic flow-record format. This new feature supports additional technologies such as MPLS or Multicast.
We also have Internet Protocol Flow Information Export (IPFIX) coming up in the near future which is based on NetFlow Version 9 but acts as a more universal industry standard.
Thursday, July 7, 2011
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