>1. in FR, when we specify clock rate for 64k, we use clock rate 64000, why >not 64 x 1024 = 65536 ? and for 1.544 mbps, we use 148000, why not 1.544 x >1024 x 1024 ?
This isn't just FR, but any connection that uses T1 signaling. At 8000 frames/s (these are T1 frames); each frame is composed of 8-bits per channel (x 24 channels) plus a framing/signaling bit (ESF). As a result, each DS0 (channel) is 64000 bits/s. This has nothing to do with the binary calculation of 2**16 which equals 65535. There is a common confusion between base10 and base2 in the computing industry - just check any Dell ad; they footnote their definition of GB to equal a "billion bytes" (Toshiba does this too - I'm sure there are others) rather than the 2**30 that we may be used to. >2. in OSPF, when config a loop back interface with address 128.10.10.10/24 >and in other router, we can see the rout to 128.10.10.10/32 ?? but if we >config an ethernet interface, it is 128.10.10.10/24, any reason ?? or simply >the behaviour in OSPF ? I don't know if this is per the RFC or just Cisco's implementation (actually, I really don't care...so I haven't bothered to look it up) but because the router sees the interface as a "loopback" type (vs. broadcast, non-broadcast, point-to-point, point-to-multipoint) it knows that there is only one "valid" address for that network and advertises the host route. This causes a classic VLSM/FLSM problem when redistributing to IGRP as the loopbacks in the OSPF domain become unreachable in the IGRP domain without taking specific steps to provide reachability. One method is to manually modify the ospf interface type of the loopback; if you change it to "point-to-point" the network configured on the loopback interface (in your example 128.10.10.0/24) will be advertised in OSPF rather than the host route. Another way to handle this is via the default-network command but that wasn't your question and it has been covered many times on this list so if you want more info about it check the archives. HTH, Ben Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=38921&t=38908 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
