From: Huan Pham (huan.pham@valuenet.com.au)
Date: Sat Feb 09 2008 - 20:15:30 ARST
Hi Scott,
I like Keith's point. Although I do agree with you, it does not matter that
much as far as QoS is concerned.
However, reference bandwidth is a part of metrics used by some IGP protocols
(OSPF, EIGRP). This BW setting decision does matter. Even if you have only
1K different between two links, one is preferred than the other. IF you do
not have consistent bandwidth settings for your T1 connections, your routing
behavior will potentially be changed (e.g. before it was load-balancing,
after you set BW, you get only one single path).
It is interesting to note, by default, the reference bandwidth for a Serial
link (with any speed) is set to a T1 speed of 1544Kbps.
R1#sh int s1/1 | in BW
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
Keeping this in mind, and the fact that 8K does not make much difference in
the QoS side, I would prefer to use Cisco default. If I have to set the BW
explicitly, I will use 1544, just to cover unexpected thing in the routing
side.
Cheers,
Huan
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Scott Morris
Sent: Sunday, 10 February 2008 7:29 AM
To: 'keith tokash'; 'Navid Daghighi'; 'Cisco certification'
Subject: RE: 1544 or 1536
In the grand scheme of things, especially in lab environments, I don't think
it matters all that much. Being 8k off one way or the other is more than
likely not going to make you drop lots of packets. Unless you have a fairly
saturated line or are THAT close to needing more. :)
But technically 24 channels at 64K a piece is 1536.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
#153, JNCIS-ER, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
Telephone: +1.810.326.1444
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-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
keith tokash
Sent: Saturday, February 09, 2008 12:40 PM
To: Navid Daghighi; Cisco certification
Subject: RE: 1544 or 1536
I've wondered this too, and haven't come up with a definitive answer (unless
they specify, which I haven't seen). 1536 is more accurate I suppose, but
some might argue the other way. I settle for making sure that whichever I
choose, I make it the same everywhere in case we're dealing with OSPF/EIGRP
decisions. Sorry for half an answer. :(
With a few exceptions, secrecy is deeply incompatible with democracy and
with science.
--Carl Sagan
> Date: Sat, 9 Feb 2008 17:03:39 +0100
> From: smart4D@free.fr
> To: ccielab@groupstudy.com
> Subject: 1544 or 1536
>
> Hi,
>
> On SGs, I see both "bandwidth 1544" and "bandwidth 1536"
>
> What criteria should be used to select one or the other ?
>
> thanks,
> Navid
>
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