Hello-I have been studying FR for a while now .cant find anywhere to answer what these numbers mean,from the show frame-relay map command----- Serial1/2 (up): ip 172.16.1.4 dlci 401(0x191,0x6410),
I am understanding that the IP is the next hop address? and the DLCI is local to the I/F you are on? but what do 0X191 and 0x6410 mean? many thanks.
0x191 = 401 = DLCI 0x6410 = 25616 = It's a mapping to the serial interface, someone may be able to confirm how this works a little bit better.
Many thanks-the DLCI is in Hex, that makes alot of sense-much appreciated.
Hi,
Actually 0x6410 is the how the number is written by the protocol: DLCI DLCI 110010|xx-0001|xxxx
The Xs represent the other header fields ( DE, EA, etc. ). If you exchange Xs with 0, you got 0x6410.
Regards, Gabriele
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So 0x6410 is the same as 401? Thanks for clearing that up-does any1 know of a good simulator for FR please? I have tried netsimk but it doesnt support it at the moment
Hi,
Yes, is 401 decimal; You you look carefully I've done a little mistake... should be 011001-0001 ( 401 ) and not as above 110010-0001 (801)
This is the format of the FR frame flag (8bits) | Address (16bits) | Data ... | FCS (16bits) | flag (8bits)
Address is: DLCI (6bits) | C/R (1bit) | EA (1bit) DLCI (4bits) | FECN (1bit) | BECN (1bit) | DE (1bit) | EA (1bit)
So, if you have DLCI 102 ( 0x66 hex, [000]1100110 bin ) you'll end up with something like this in the address field 000110[00] 0110[0011] ( DE bit and the last octet EA bit are set )
that is 0x1863. IOS will return 0x1860 'cause it apply a mask leaving only the 10bit DLCI address ( 0x1863 and 0xfcf0 )
Note that I do not think you'll go to this kind of "details" on the exam ( it is pretty meaningless )... so when you know that 102 is the DLCI and it is a 10bit address I think it suffice
I've not used any simulator personally, but sometimes I've read about Bosom Sim used by people pursuing cisco certs.
Regards, Gabriele
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Many thanks-I hope to be as knowledgeable as you -through much study and hard work.
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