From: Tom Lijnse (Tom.Lijnse@globalknowledge.nl)
Date: Mon Sep 05 2005 - 13:02:38 GMT-3
Hi Simon,
Your understanding was actually correct at one point in time.
The behavior of the 'bandwidth percent' has been changed (on non-7500
platforms) from IOS 12.1T/12.2 to 12.2T/12.3
In 12.1T/12.2 'bandwidth percent' is a percentage of the remaining
bandwidth (which defaults to 75% of the interface bandwidth).
In IOS 12.2T/12.3 'bandwidth percent' is a percentage of the interface
bandwidth.
For more details look at:
http://www.cisco.com/en/US/tech/tk39/tk48/technologies_tech_note09186a00
800fe2c1.shtml
Regards,
Tom Lijnse
CCIE #11031
Global Knowledge
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
simon hart
Sent: woensdag 31 augustus 2005 20:23
To: Chris Lewis (chrlewis); simon hart; ccie2be; Group Study
Subject: RE: absolute or percentage - will it cost points?
Hi Chris,
Thanks for the input. I am glad you have pointed this out, as it has
certainly corrected my understanding of the two commands.
I configured along the same lines as yourself, however I created 3
classes
under one policy. Each class is given percent 25. The show policy
interface
certainly shows that 2500 has been allocated as the guaranteed
bandwidth.
If I try and add another class with percent 25 I recieve an error
message:
Rack1R5(config-pmap)#class ICMP
Rack1R5(config-pmap-c)#band
Rack1R5(config-pmap-c)#bandwidth percent 25
I/f Ethernet0/0 class ICMP requested bandwidth 25%, available only 0%
From this I take the following assumption. Bandwidth 25% takes 25% of
total
bandwidth = 2500. However one can never assign more than 75%, i.e. more
than three bandwidth percent 25 commands (or whatever config that adds
up to
75).
Thus bandwidth 2500 and bandwidth percent 25 amount to the same thing
if
the total interface bandwidth is 1000. I believe the reason for the
introduction of the bandwidth percent command is the transportability of
a
configuration amongst different interfaces, and for interfaces where the
bandwidth may vary.
Thanks Chris
Simon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Chris
Lewis (chrlewis)
Sent: 31 August 2005 18:53
To: simon hart; ccie2be; Group Study
Subject: RE: absolute or percentage - will it cost points?
Hello Simon,
I read your reply and it made sense to me, however I tried it out on a
router and the results do not seem to agree.
In the configuration below, I create an arbitrary class (OK I wouldn't
use bandwidth for voice traffic in a real deployment, but that's not
important here) just to see the effects of the bandwidth and bandwidth
percent, then use show policy-map interface to check what the router is
doing.
From this output it appears that the two commands do in fact give an
equivalent result in terms of claiming 2500kbps is reserved for the
class defined.
How to reconcile the two views?
Router1(config)#class-map voice
Router1(config-cmap)#match ip rtp 16383 16383
Router1(config-cmap)#exit
Router1(config)#policy-map pm1
Router1(config-pmap)#class voice
Router1(config-pmap-c)#bandwidth percent 25
Router1(config-pmap-c)#int e0/0
Router1(config-if)#service-pol out pm1
Router1(config-if)#do sho policy int
Ethernet0/0
Service-policy output: pm1
Class-map: voice (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip rtp 16383 16383
Queueing
Output Queue: Conversation 265
Bandwidth 25 (%)
Bandwidth 2500 (kbps) Max Threshold 64 (packets)
(pkts matched/bytes matched) 0/0
(depth/total drops/no-buffer drops) 0/0/0
Class-map: class-default (match-any)
1 packets, 60 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Router1(config-if)#no service-pol out pm1
Router1(config-if)#no policy-map pm1
Router1(config)#policy-map pm2
Router1(config-pmap)#class voice
Router1(config-pmap-c)#bandwidth 2500
Router1(config-pmap-c)#exit
Router1(config-pmap)#int e0/0
Router1(config-if)#service-pol out pm2
Router1(config-if)#do sho policy-map int
Ethernet0/0
Service-policy output: pm2
Class-map: voice (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip rtp 16383 16383
Queueing
Output Queue: Conversation 265
Bandwidth 2500 (kbps) Max Threshold 64 (packets)
(pkts matched/bytes matched) 0/0
(depth/total drops/no-buffer drops) 0/0/0
Class-map: class-default (match-any)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Config of router this was run on (no max reserved bandwidth configured).
policy-map pm2
class voice
bandwidth 2500
!
!
!
interface Loopback0
ip address 192.168.1.1 255.255.255.0
!
interface Ethernet0/0
ip address 172.16.136.1 255.255.255.192
service-policy output pm2
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
simon hart
Sent: Tuesday, August 30, 2005 2:06 PM
To: ccie2be; Group Study
Subject: RE: absolute or percentage - will it cost points?
Hey Tim,
Getting into the swing of things again.
Your question below will depend on other factors, however looking
straight off they are not the same.
When applying a policy to an ethernet interface the IOS will default the
available bandwidth to the 75% of the actual interface bandwidth.
Therefore
Bandwidth 2500 does not equate to 25% of the bandwidth but will equate
to
(2500/7500) * 100 = 33.33%
Whereas applying Bandwidth percent 25 will equate to 25% of 75% of
available interface bandwidth = 1875
Now if you were to apply the following command to interface e0
max-reserved-bandwidth 100
Then both bandwidth 2500 and bandwidth percent 25% would be equivalent
In the exam I would err on the side of caution and use the bandwidth
percent 25. Also for good measure would probably ask the proctor for
clarity.
Simon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
ccie2be
Sent: 29 August 2005 20:06
To: Group Study
Subject: absolute or percentage - will it cost points?
Hi guys,
Here's another interpretation question.
If told to reserve 25% of the bandwidth on a ethernet interface for a
certain type of traffic, will both of the below config's score points?
policy-map
class xxx
bandwidth percent 25
policy-map
class xxx
bandwidth 2500
From a network point of view, they both accomplish the same exact thing,
but from a lab scoring point of view, are they both equal?
TIA, Tim
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