From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Wed Aug 31 2005 - 14:52:56 GMT-3
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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