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Interview question

 
 Some one explain the answer for the below question which was asked in interview
1 What is mean by reliability..  value 255 denotes?
 
2. What is the difference between AD and metric?
 
3. Tell me the one feature which Router supports but switch(L3) doesn't support?

 

  • WAN Routing and Switching
6 REPLIES

1. 100% reliable...2. The

1. 100% reliable...

2. The router will use AD to choose which route is put into the table. The lower is more preferred. The metric is used when the route is learned from the same protocol and is used as a tie breaker so-to-speak. For example:

Route 192.168.1.0/24

OSPF, with an AD of 110, learns route 192.168.1.0/24 with a metric of 20

EIGRP with an AD of 90, learns route 192.168.1.0/24 with a metric of 1000

EIGRP learns of another path to 192.168.1.0/24 with a metric of 950.

 

All things being equal, the router will first check AD and determine EIGRP will be the better protocol to use, but because EIGRP has two routes, it now has to determine which has the lower metric. The 3rd path will win and the route will be put in the table with a [90/950]

3. Only one thing I can think of off of the top of my head and that would be NAT, but that also depends on the platform.

HTH,

John

HTH, John *** Please rate all useful posts ***

why we using 255 , why cant

why we using 255 , why cant use 300,400 ,500 so on.. what is 255 denotes.. 1/255 for tx load and 1/255 for rx load.. how u can it was reliable what is mean by it.. could explain it..

 

3. ipsec also wont support in L3 swicth

Super Bronze

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Posting

Why 255?  Hint, think 1 byte (8 bits) and binary.

#3

IPSec - that too would depend on the "L3 switch".  (BTW, remember there are network hardware vendors other than Cisco, so even if none of Cisco's L3 switches supported IPSec [which I don't know is true or not], another vendor's L3 switch might..)

Super Bronze

DisclaimerThe Author of this

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

#1

If I remember correctly, reliability measures interface state changes.  255 is the highest values, i.e. 100% - no state changes.

 

#2

AD is the measure of trust assigned to a static route or a routing protocol.  For example, eBGP route information is normally preferred over IGP route information (for the same prefix).

Metric is the measure of "cost" from router to a prefix within the same dynamic routing protocol.  Generally used to select the "better" path, when there's more than one path to the same prefix.  For example, RIP uses hop count as its metric.

 

#3

Well that really depends on the "router" and the "L3 switch".  Usually routers will support more media types than L3 switches, which often only support Ethernet.  Also routers often will support more "features", e.g. advanced QoS, than a L3 switch.  The "true" difference (laugh) is how the vendor labels them.  For example, the 6500 is a "L3 switch" and the 7600 is a "router", but their chassis could have the same exact line cards, the same exact supervisor, and (used to) run the same exact IOS.  (NB: mind you, the 6500 supported service modules that the 7600 would not, and the 7600 supported "WAN" line cards that the 6500 would not, but these differences were more likely due to marketing rather than hardware technical limitations.)

Hall of Fame Super Gold

1 What is mean by reliability

1 What is mean by reliability..  value 255 denotes?

This is a "trick" question.  Old school & very relevant (even until today).  

 

Why a trick question?  Which one has the value of "255", the nominator or denominator?   Reliability of the line is measured with both the nominator and denominator value of 255.  BOTH must have a value of 255, or 255/255.  If you get either one of the value that is LESS THAN 255 that means you've got a serious line problem.   This is why I'm saying that this is a trick question.  As a candidate it is YOUR JOB to ask the interviewer to be more specific.  This means you, as a candidate, know your stuff. 

3. Tell me the one feature which Router supports but switch(L3) doesn't support?

NAT is supported on a router.  Layer 3 switches DO NOT support NAT. 

3 router can support voice

3 router can support voice cme h323 sip mgcp.    switch doesnt

 

but switch support macsec

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