Cisco 3750 switch throttling and prioritizing traffic

travisryan
travisryan used Ask the Experts™
on
My company has run of 100 Mbps private between two locations. On either end is a 3750 switch. I believe there is finally enough traffic between the locations that I need to do some throttling and prioritizing so critical applications can still talk during the time our backups run.

I realize this would be better served by plugging both ends into routers but I'd like to try and make it work with the switches as I'd need to change my network architecture around.

Below is my code. My two questions are: 1) The policy is applied to the interface connecting to the fiber, yet when I run sh policy-map int gig 4/0/47 I get 0's for everything like nothing's being processed. 2) How do I prioritize Class A traffic?


ip access-list extended priority_list
permit ip host 15.5.5.31 any
permit ip host 15.5.5.39 any
permit ip host 15.5.5.10 any

ip access-list extended non_priority
permit ip any any

class-map Class-A
match access-group name priority_list

class-map Class-B
match access-group name non_priority

policy-map priority-policy
class Class-A
police 95000000 8000 exceed-action drop
*
prioritize this traffic*
class Class-B
police 40000000 8000 exceed-action drop
*
do not prioritize this traffic*

int Gig 4/0/47
service-policy input priority-policy
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kevinhsiehNetwork Engineer

Commented:
First of all, you need a policy to classify traffic. You have most of it, but not all of it. My classification policies actually mark traffic with DSCP tags. I don't know if what I have will work.

policy-map classify-policy
class Class-A
class Class-B

! on all interfaces where traffic can arrive on, you need to classify the traffic on ingress
interface range g4/0/1-48
service-policy input classify-policy

! on the egress interface where you want to control the traffic, apply your output policy
int g4/0/47
desc fiber connection to mpls
service-policy output priority-policy

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Author

Commented:
Kevin, I'm not sure I follow. I have an access list, a class map, a policy map, then I apply that policy to an interface with these lines:

int gig 4/0/47
service-policy input priority-policy


What else am I missing?
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kevinhsiehNetwork Engineer
Commented:
I think you need two policy maps. At least I do. The first is on ingress traffic to do classification. The second is on egress traffic to give priority bandwidth and shaping.

Author

Commented:
Kevin, on a switch (at least the 3750) you can't put an egress policy on an interface:

LocationASwitch(config-if)#service-policy output priority-policy
police command is not supported for this interface
Configuration failed!
Warning: Assigning a policy map to the output side of an interface not supported

Author

Commented:
Let me also add that from some of my bandwidth monitoring it looks like the policy is in effect eventhough when I run "sh policy-map int gig 4/0/47" it's showing "0 packets, 0 bytes""5 minute offered rate 0 bps, drop rate 0 bps" which makes me even more confused.

Author

Commented:
I applied a policy to the other end of our fiber connection between locations thinking this was a directional problem, but that didn't change anything. Also, running a "sh policy-map" on this interface showed the same "0 packets, 0 bytes" results as the other policy. Below is that configuration. Any help is appreciated.

ip access-list extended LocationB_priority_list
permit ip any host 10.1.1.31
permit ip any host 10.1.1.39
permit ip any host 10.1.1.10

ip access-list extended LocationB_non_priority
permit ip any any

class-map LocationB-Class-A
match access-group name LocationB_priority_list

class-map LocationB-Class-B
match access-group name LocationB_non_priority

policy-map LocationB-priority-policy
class LocationB-Class-A
police 95000000 8000 exceed-action drop

*prioritize this traffic*
class LocationB-Class-B
police 40000000 8000 exceed-action drop

*do not prioritize this traffic*

int Gig 1/0/47
service-policy input LocationB-priority-policy

Author

Commented:
Since I'm not familiar with any part of the process I'm breaking it down into it's parts. I tried a simple:

ip access-list extended test
permit ip host *computer a* any
deny ip host *computer b* any

conf t
int gig 1/0/40
ip access-group test in


And that works, so I know I've got my ip access list section configured correctly so it has to be something down the line.

Author

Commented:
After speaking to a consultant that specializes in Cisco it seems like he's stumped for the moment as well. That makes me feel better and worse at the same time.
This ended up being an issue where the prioritizing was assigned to the wrong interfaces, they needed to be assigned to the interfaces on the other end of my communication link.

Author

Commented:
This was the clear solution to the problem.

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