Qos - Precedence in a policy map

[cccnetwork1]

Hello ,

I'll try to be brief  :

I've a number of class-maps , based on access groups , some of which are overlapping  eg  Proxy  ---- permit any to host 10.10.10.10

VIP - permit 10.1.1.0 /24

I want VIP to be dscp ef

Proxy  to be  dscp 33

Policy-map xxxxxx

class VIP

set dscp ef

class Proxy

set dscp 33

if a host on 10.1.1.0 talks to proxy 10.10.10.10  which dcsp value is assigned ?

i know I could add a further class-map match all  , but this is a small example for a compliacted scenario .

when a packet could be in a number of classes is there a firstmatch / bestmatch  , and does this then continue to policy-map positioning of class

Any advice would be much appreciated .

[John Blakley]

The classes in a policy map are matched in order. For example, if you had the following:

class HTTP

permit 10.10.10.0/24

class HTTP-Dif

permit 10.10.10.10/32

policy-map Web

class HTTP

set dscp ef

class HTTP-Dif

set dscp default

The 10.10.10.0/24 subnet will be set for EF and the host 10.10.10.10 wouldn't match the HTTP-Dif. To fix that, you would need to remove the policy-map from the interface and rearrange your class maps:

policy-map Web

class HTTP-Dif

set dscp default

class HTTP

set dscp ef

Now the host will get the appropriate marking, and what doesn't match in the 10.10.10.0/24 subnet will hit the HTTP class.

HTH,
John

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[Jon Marshall]

Hi John

Could i ask a favour ?

I am involved in a thread where a guy is having problems with routing. The thread is quite long and i think we have found the problem with his setup but the only way to fix it (that i can see) is to do a sort of conditional route advertisement with EIGRP. There may be another way that i have missed but if not i was wondering if there was a way to use EEM to only advertise the route under certain conditions ie. when an 1841 router is actually connected up in this case.

If you have the time can you have a look and see if there is a possible solution.

https://supportforums.cisco.com/thread/2254631?tstart=0

Thanks

Jon

[cccnetwork1]

John - thanks for that - could I summarise as marking depends on a first match in the policy map

[John Blakley]

Yes, that would be correct.

HTH,
John

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