When dealing with CIRs directly onto your Cisco gear, packet shaping is your best friend.

This means if you have 100Mbps circuit connect to a Gig interface, the router will send at a Gig. One resolution will be to set the speed of the interface to 100Mbps. The 64k$ question is, what happens when your CIR 150 Mbps… this is where shaping plays an integral part.

Step 1: Create a Policy Map

This policy may is in bits per seconds and is for 95% of my 150Mbps CIR circuit

 policy-map OPT-SHAPING-150
class class-default
shape peak 140000000

 Step 2: Applying the above Policy Map to the outgoing/incoming interface

 interface GigabitEthernet0/2

 service-policy output OPT-SHAPING-150

 Step 3: Verify

 sh policy-map interface g0/2

 Service-policy output: OPT-SHAPING-150
Class-map: class-default (match-any)
9 packets, 3432 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: any
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 9/681
shape (peak) cir 140000000, bc 560000, be 560000
target shape rate 280000000

Leave a Reply