RE: clock rate [7:38908]
Ellis, Point 1 . Pass Point 2. Loopbacks in ospf are always advertised as stub networks, ie: /32 routes. You can change the network type on the loopback by using the command ' ip ospf network point-to-point ' the route will be seen by others as a route to a subnet. HTH Richard Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=38912t=38908 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: clock rate [7:38908]
1. Because its 64000 bps, built by humans, not computer memory. 3. huh? Note that if you earn 50k you will get 5 (less tax) Marc Ellis Lam wrote: Two Qs, 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 ? 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 ? Thanks Ellis Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=38915t=38908 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: clock rate [7:38908]
[Question] 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 ? Partial answer: Transmission speeds are in bits per second (temporal), storage is in bytes (spatial), although you'll find reference to octets (usually not expressed as bytes) in the speeds when they're discussing frame formats. When you see 1.544 mbps, it's 1.544 x 10^6 = 1.544 x 1000 x 1000. As long as you're measuring speed, you don't make a conversion from a decimal number to a power-of-2 number. The 1.544 mbps came from the original T carrier system, when we had T1, T2 (4 x T1) and T3 (28 x T1) encapsulations (or whatever it was called) and DS0 (64 kbps), DS1 (24 x DS0), DS2 (4 x DS1) and DS3 (28 x DS1) speeds. If I remember correctly, the T carrier system was deployed way back in the 1960's in the US, and in Europe as the E system. The research was probably finished at Bell Labs and the universities in the 1950's; they also had specifications for optical that we are still trying to figure out how to deploy. Those old guys were pretty smart, especially when you consider the state of the art at that time. The DS0 speed came from 8 x 8000 = 8 x 8 kHz. That works out to a speed of 1,536,000 bps when you combine 24 DS0 channels. Adding 8000 bps (8 kbps) for framing gives 1,544,000 bps or 1.544 mbps. To say that DS1 is 24 DS0 channels is slightly misleading unless you realize that the extra 8 kbps framing is implied. You'll have to do some mulitplication to check the DS2 and DS3, and look up some of the old books (this is considered ancient history now). I have no idea what to say about 148x 10^x. Where did you get that? -- TT Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=38917t=38908 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: clock rate [7:38908]
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=7i=38921t=38908 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
