TCS INTERVIEW: NOC ENGINEER, L2


COMPANY NAME : TCS

TIME OF INTERVIEW: NOV, 2013

PROFILE: NOC ENGINEER , L2


 

SWITCHING

What is the role of Native VLAN ?

Ans.

VLAN simply divides broadcast domain.

Every VLAN has got identification, which is present in frame structure.

Native VLAN is untagged or in layman language, simply it is similar to the logic of default route.

Reference Link

https://learningnetwork.cisco.com/thread/8721

 

What all are the configuration required on a port, if IP phone has to be connected on Switch port ?

 

Can we assign two subnets to a single VLAN ?  if not, what is the problem ?

Ans.

No, we cannot assign two subnets to a single VLAN.
To prove this statement, go inversely.

If we assign two subnets to a single VLAN. Then, for two different subnets, there will be two different SVI’s or Layer 3 VLAN exit points.

This situation leads to ambiguity that if traffic has to go outside VLAN, then host traffic will consider which SVI or exit point to go outside.

 

Can we further divide Broadcast domain of a VLAN ? If possible, How ?

Ans.

Yes we can divide a single broadcast domain further using concept of Private VLAN.

In case of Private VLAN’s, we assign different roles to the ports.

Reference

https://networkproxy.wordpress.com/2014/10/18/fb-discussions-switch-port-communication/

 

What is the benefit if having more than one switch in Server Mode ?

Ans.

Simply, we will be having more than one point of manageability in the network, for VLAN’s.

How to make Revision number zero on a switch ? Why its recommended to connect new switch in the network, with Revision number zero ?

Ans.

Recommended: New switch must be connected to the network in Client Mode and Revision Number=0

How to make Revision number=0?

Change VTP domain name to any bogus name(fake name) and then again change to required VTP domain name

Reference

https://networkproxy.wordpress.com/2014/03/20/vtp-concept-basic-general/

 

If any physical port in a Port-Channel goes in suspended state. What all are the possibilities?  Any scenario in which you faced some issue related to the Port Channel ?

 

How STP converges, explain complete process. Try some Three switches connected  in triangle with Dual links between them. What will be the port states ?

 

Any issue, you have faced where loop is formed ? How you detected & troubleshooted the loop ?

 

Difference between STP & RSTP. Why RSTP converges faster than STP.  if you answer in RSTP number of states are less , why ?

 

Explain How HSRP is implemented in you network. Complete scenario including Hosts, switches, Virtual gateway & all ?

 

HSRP do Load Balancing or Load sharing ?


PRACTICAL SCENARIOS

If user is not  able to acess any server in the network, what all are the troubleshooting steps ?

 

How to check communication between two VLAN’s ?

 

In a switch, switch A is in Server mode with Revision number 10 &   switch B is in Client mode with Revision number 20. which Switch will override VLAN database of another ?

 

How to check if routes are flapped or not ?

Example: OSPF is running.  Command: sh ip ospf neighbor do not show any flap with neighbors. But, learned routes got flapped. How ? 

 


 

GENERAL

How trace route works ? Can we check load Balancing is happening between two devices using trace route command 

 

How Hosts connected to two different switches. Explain process. Consider remaining details by Yourself ?

 

How ARP works ?


 

HARDWARE 

In 6500, in which slots SUP are connected. what is the SUP model. What is the purpose of  MSFC card in switches ?

 

In Nexus, how throughput got increased. What is new in Nexus ?

 

How port security can be done ?

 

Explain DHCP snooping ?

 

What is MAC binding. How to do it ?

 

If user is not able to  get IP from DHCP. What all are the troubleshooting steps ?

***************

ROUTING 

 

OSPF

If OSPF gets stuck in Exstart/ Exchange state. what is the possible reason ?

 

Why OSPF is called Link state ?

 

In OSPF, can we do Load Balancing. If possible, How? Any scenario ?

 

Why area o is required ?

 

Can we do summarization of LSA-1 ?

 

In  NSSA, suppose ABR  = ASBR.  

 

ASBR  received routes from any other protocol. If we don’t want to allow ASBR or  ABR to allow these received routes to gets transferred to other areas, how to stop ? 

 

BGP

Why BGP is required ?

 

Why iBGP is required ?

 

To run iBGP, why IGP is required ?

 

How to check outgoing routes, after applying Route-Map?

 

How to check Incoming routes, after applying Route-Map?

 

Some Multihoming scenario?

 

Explain BGP states?

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