[c-nsp] Cisco 3550 counters and QoS

[Marco Matarazzo]

> Have you factored in the packet overhead for your dot1q trunk?

No I didn't, and I don't think it's the case... in fact I'm seeing LESS
traffic on the trunk than on the layer3 interface... and the correct traffic
counter is that on the trunk. The layer3 interface is not tagged, it's not
an SVI otherwise I could even think about having right counters on that one!
:D

Also, last time I checked the overhead of dot1q tagging was way lover than
20%! ;)

Thanks,
]\/[arco
>
>
> Marco Matarazzo wrote:
> | Hi all,
> |
> | usual question about counters... ;)
> |
> | I've setup a 3550-48 SMI in a lab, one port is a layer3 port, the
> other one
> | a layer2 trunk to the rest of the network.
> | I've applied an inbound and an outbound policy to the layer3 port, to
> police
> | the traffic at 1Mbps. This is the relevant part of the configuration:
> |
> | IOS (tm) C3550 Software (C3550-I9Q3L2-M), Version 12.1(22)EA1, RELEASE
> | SOFTWARE (fc1)
> |
> | mls qos
> |
> | class-map match-any all_traffic
> |   match ip dscp 0
> |
> | policy-map 1MbpsIN
> |   class all_traffic
> |     police 1024000 192000 exceed-action drop
> | policy-map 1MbpsOUT
> |   class all_traffic
> |     police 1024000 192000 exceed-action drop
> |
> | interface FastEthernet0/2
> |  description CustomerPort
> |  no switchport
> |  ip address x.x.x.x 255.255.255.0
> |  service-policy input 1MbpsIN
> |  service-policy output 1MbpsOUT
> |  no cdp enable
> |
> | interface FastEthernet0/48
> |  description TrunkCust3Gig1
> |  switchport trunk encapsulation dot1q
> |  switchport trunk allowed vlan 1,6,1002-1005
> |  switchport mode trunk
> |
> | Now the weird part:
> |
> | If I download anything on the customer machine, traffic gets policed at
> | 1Mbps (5 minute average, I'm using the usual mrtg), and I can see on the
> | graphs a nice almost flat line on egress on the layer3 interface, and
> a nice
> | almost flat line on ingress on the trunk. All fine.
> |
> | If I upload anything from the customer machine, the traffic gets
> policed at
> | 1Mbps, but on the graphs, I see on the ingress of the layer3 interface
> | 1.20Mbps, and on the egress of the trunk the nice flat line at 1Mbps.
> | Checking the ftp client, I can see it's uploading at 125KBps (that's
> | 1Mbps!), checking the "sh int":
> |
> |   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
> |   Queueing strategy: fifo
> |   Output queue: 0/40 (size/max)
> |   5 minute input rate 1270000 bits/sec, 107 packets/sec << Should be
> lower!
> |   5 minute output rate 39000 bits/sec, 68 packets/sec
> |
> | Now, it wouldn't be a big problem (traffic gets policed correctly
anyway),
> | but billing on the layer3 counters becomes impossible, as there's a 20%
> | difference on real traffic used! It there something wrong I'm doing? Any
> | ideas?
> |
> | Thanks!
> | ]\/[arco
> |
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> : Anthony D Cennami
> : Managing Partner
> : NeuPATH, LLC
> : acennami at neupath.com
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