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09-05-2017
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09-11-2017
09:48 PM
I do definitely know the differences between NVRAM and Flash memory. I did googled for past few days, but I was not able to find the 100% satisfying answer. Some people said that nowadays, people can actually store the startup configuration file in Flash. Others said no because of booting process plus because of the speed(NVRAM is faster than Flash). I am just wondering why smart people invented NVRAM. + Why can't the router just load IOS from flash and then get the startup configuration file from flash, and skip the NVRAM? P.S. After pondering, I figure out why we should not save the startup configuration file in FLASH Memory. I am not 100% sure, but I am 99% sure. It is because of configuration register value :) If you carefully look at these two register value [0x2102 and 0x2142], you would agree with me. If you don't agree with me, please share with me your thoughts :)
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09-11-2017
05:35 PM
How PC A segments the 9000 byte according to link MTU? If PC A segments the 9000 byte according to MSS or fragments the 9000 byte according to MTU, I do understand. Segmentation and MTU do not match according to what I have learned from ICND 1.
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09-11-2017
04:33 PM
So, PC B will get only 240 byte of data out of 9000 byte since the data received from PC A is bigger than PC B's MTU size. Plus, then in this case, PC A doesn't segment the 9000 byte data in L4 and litterally pass to L3, and then fragment at L3?
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09-11-2017
04:30 PM
Thank you very much. She actually said that BPDU is from OSI model and other protocols I have learned from ICDN 1 are from TCP/IP. I honestly don't get, but she concluded that protocols from OSI model are used to create a net and protocls from TCP/IP are used for communication.
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09-11-2017
04:29 PM
He actually said that BPDU is from OSI model and other protocols I have learned from ICDN 1 are from TCP/IP.
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09-11-2017
05:27 AM
I do know the differences between both. I want to know why startup configuration file is stored in NVRAM if it can be stored in Flash? This link shows the router's booting process: http://www.9tut.com/cisco-router-boot-sequence-tutorial Why cannot router just load the IOS and get the startup configuration file in Flash memory?
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09-11-2017
05:24 AM
I mentioned PC A's and PC B's MSS so that you have an idea how PC A will segment 9000 byte data. I am just wondering that 9000 byte doesn't get segmented in UDP communication in L4? If not, how PC A sends 9000 byte of data to PC B without segmenting or fragmenting the data?
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09-11-2017
03:04 AM
Lastly, this is probably really a stupid question. Recently, I figured out that ARP has four brothers. The one I discovered by playing with GNS3 was 'Gratuitous ARP'. I am not sure but this is how I understood the gratuitous arp. If I try to use a public IP which someone is already using, I won't be able to use it because of gratuitous ARP. I heard that 1 public ip costs around 50 bucks (not sure). I guess that ISPs have a huge public ip pools and obviously some of public ip addresses are not being used. If I can figure out that whether a certain public ip is being used or not through gratuitous ARP, is it possible to use a public ip without paying 50 bucks to ISP?
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09-11-2017
01:46 AM
I know that Flash memory is used to store the images of the IOS and NVRAM is used to store the startup-config file. But when my net instructor asked me, "Why cannot you just save the startup configuration file in Flash?", I was not able to answer. If you know how to answer that question, please let me know :) I also would like to know functional differences between FLASH Memory and NVRAM.
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09-11-2017
12:39 AM
PC A has a 1500 byte MTU size and 1460 byte MSS size. PC A needs to send 9000 byte of data to PC B. PC B has a 1400 byte MTU(I am not 100%, but I heard MTU size can be changed) size and obviously 1360 byte MSS size. PC A will segment 9000 byte of data into 6 1460 byte and 1 240 byte, then send all 7 segments to PC B. Since first 6 packets' size is bigger than PC B's MTU size, PC B would discard them. But since the last packet size is less than PC B's MTU size, PC B will take that last packet. If my understanding or explanation is wrong, please please let me know. P.S. If you know how to simulate that senario in the packet tracer, please let me know :)
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09-10-2017
07:46 PM
WOW!!!! Thank you very much. Again, I learned things I cannot learn from the textbook. But, it is pretty sad that Router2 drops the ICMP Reply which Router2 constructed for PC1. I guess it is generally better to construct the Reply packet first and then check the routing table. But, in this case, it would have been better if Router2 checks the routing table first. In that case, Router2 doesn't have to constrcut the Reply packet and furthermore doesn't have to drop its own Reply :) On the other hands, I also think it could be a bad idea if the destination is reachable. In that case, Router 2 needs to look up the routing table twice. If my assumptions are not 100% correct, please let me know. I am always waiting to get enlightened :)
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Created by
169.254.X.Y
in Switching
09-11-2017
09-11-2017
I do definitely know the differences between NVRAM and Flash memory. I
did googled for past few days...
09-11-2017
How PC A segments the 9000 byte according to link MTU? If PC A segments
the 9000 byte according to M...
09-11-2017
So, PC B will get only 240 byte of data out of 9000 byte since the data
received from PC A is bigger...
09-11-2017
Thank you very much. She actually said that BPDU is from OSI model and
other protocols I have learne...
09-11-2017
He actually said that BPDU is from OSI model and other protocols I have
learned from ICDN 1 are from...
Created by
169.254.X.Y
in Switching
09-11-2017
09-11-2017
I do know the differences between both. I want to know why startup
configuration file is stored in N...
09-11-2017
I mentioned PC A's and PC B's MSS so that you have an idea how PC A will
segment 9000 byte data. I a...
09-11-2017
Lastly, this is probably really a stupid question. Recently, I figured
out that ARP has four brother...
09-11-2017
I know that Flash memory is used to store the images of the IOS and
NVRAM is used to store the start...
09-11-2017
PC A has a 1500 byte MTU size and 1460 byte MSS size. PC A needs to send
9000 byte of data to PC B. ...
Public Statistics
| Date Registered | 09-05-2017 07:57 PM |
| Date Last Visited | |
| Total Messages Posted | 41 |
Helpful Votes Given To
| User | Helpful Count |
|---|---|
| 15 | |
| 25 | |
| 10 | |
| 20 | |
| 5 |
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