high CPU utilization in 7606 with SUB7203BXL with full internet table

Unanswered Question
Feb 12th, 2009

we have two Internet Gateway 7606 with Sub720-3BXL , that peering with many service providers( more than 7, total uplinks 3G)running full internet routing table, we are facing high cpu utilization more than 35 %. we want to solve this issue since we will peer with more internet service provider, if we upgrade our routers to 12406 with PRP2 can solve the cpu utilization problems and the PRP2 can reduce the cpu utilization to less than 5%.thanks

I have this problem too.
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Giuseppe Larosa Thu, 02/12/2009 - 23:55

Hello Ahmed,


sh proc cpu sorted 1min

to see what processes use more cpu

if you like you can post the output here.

Hope to help


saeedbakh Fri, 02/13/2009 - 00:28

I don,t have access now, but i know that BGP Scaner some times make that reach 50 %, but my question is the 12406 with PRP2 CAN give better cpu utilization and performane than 7606 with sub720-3BXL.



Giuseppe Larosa Fri, 02/13/2009 - 01:13

Hello Ahmed,

the PRP2 cpu should be more powerful but also the BGP configuration can take a role: the BGP scanner frequency can be changed (or it has been reduced).

Hope to help


saeedbakh Fri, 02/13/2009 - 00:33

i am asking this qustion because i can see the 7606 with sup720-3BXL in the data sheet giving 480G total throughput and 40G per slot bandwidth, and up 240Mpps forwarding.

but 12406 with PRP2 as the data sheet can give 120 Capacity bandwidth and 10G per slot capasity ,also 4.4 Mpps forwarding.

Giuseppe Larosa Fri, 02/13/2009 - 01:23

Hello Ahmed,

however when dealing with internet connections you have two dimensions:

signalling plane: number of routes memory and cpu usage

forwarding plane: volume of traffic that can be handled

The two are not closely related so a device like GSR with PRP2 can be stronger on the signalling plane (a better cpu, more memory) and weaker on the forwarding plane.

This happens normally when comparing routers and multilayer switches: switches are better in forwarding and routers have more features and/or capacities in the signalling plane.

It is unlike that you need 400 Gbps thruoghput to/from internet.

You may think to upgrade to

RSP 720-3CXL or to Sup720 3CXL.

cpu of RSP is more powerful



This because you have already a C7600 chassis.

Another possible suggestion is to double the node number and to place some providers on the new node.

This can help as well and we are already doing it.

Hope to help


saeedbakh Fri, 02/13/2009 - 01:41

really i am confused ,do you think the the GSR 12406 with PRP2 is more powerful than RSP 720-3CXL or not?

because we have already plan to use 12406 i am just worry that if we install the 12406 with PRP2 we will not reduce the CPU utilization that we are facing on the current 7606 sup720-3BXL(30 %CPU UTILIZATION),please let me know also if the forwarding for the packet to the ISP internal core will be better for the 12406 ALSO with (SIP-601 AND 10 port 1G SPA),than using the existing 7606 with SUB720-3BXL.THANKS

saeedbakh Fri, 02/13/2009 - 01:48

one point i have to mention here that we havle already two 7606 with sup720-3BXL ,

but we have alot of STM1 links and E1 the total number of uplinks to the internet is 15 uplinks , and the total bandwidth is 3.2G total .


Giuseppe Larosa Fri, 02/13/2009 - 01:50

Hello Ahmed,

if you have already ordered the GSR with PRP2 it is a good choice.

the high CPU utilization can be the result of:

relative high number of upstream providers (as I said using two nodes can help)

and of some tuning on configuration.

If cpu usage is 30% it can be reduced but it is difficult to say how much it is reduced.

You may find out that leaving one or two upstream providers on the current C7600 and moving the others to the new node is the best scenario (divide and conquere approach)

The forwarding plane is not a problem with any solution even the current device has no forwarding problems even at 10GE scale links

Hope to help


saeedbakh Fri, 02/13/2009 - 02:04

Thank you Giuseppe, so i understand for sure that two 12406 with PRP2 can reduce the CPU utilization less than 30 % (let say can be 10 %),and can handle more than 1000,000 routes,and also the SIP-601 with 10 PORT 1G can do good in the forwarding traffic to the internal network of the ISP.

what is the maximum traffic can be forwared,

just to let you know that we will use per chassis 2X SIP601. inside each SIP601 will be SPA-10 Port 1G SPA , 2 PORT STM4-SPA and 4 PORT STM1-SPA.


saeedbakh Fri, 02/13/2009 - 02:24

small questions i find in the data sheet of the SIP-601 that the route memory is 2GB , and the packet memory is 256 MB,

What is the mean on the SIP-601 since the route memory is on the PRP2. and what is the Packet memory here mean is 256MB memory for packet not a small size which can effect the forwarding here.



Giuseppe Larosa Fri, 02/13/2009 - 02:44

Hello Ahmed,

being the GSR a totally distributed architecture the linecard has a main memory to host a whole copy of the CEF table.

The packet memory is instead a memory used to handle packets during forwarding

So you should be fine with a 2GB main memory on the linecard.

Hope to help


saeedbakh Fri, 02/13/2009 - 03:14

Thanks, so 256MB packet memory does not have any impact on the forwarding for the SPA-10 Port 1G?.

Also,what is the difference between the SPA-10 PORT IG and (line card 4GE-SFP-LC 4-Port Gigabit Ethernet ISE Line Card)

which one more powerful forwarding, and what exactly the differnce between them either feature or any thing else.



Giuseppe Larosa Fri, 02/13/2009 - 08:44

Hello Ahmed,

here it is the datasheet for standard linecards


here are the SPA


and the serial interface processors that host the SPA adapters


if you connect to your providers with GE links you can use the standard interfaces that are cheaper.

SIP/SPA combinations can provide more flexibility and note that WAN SPAs may require SIP-400 and SIP-600 is able to support the 10GE SPA or 10 port 1GE SPA.

Hope to help


saeedbakh Fri, 02/13/2009 - 13:40


what is the different between SIP-600 and SIP-601 , i want to know is SIP-601 better as feature and forwarding rate than SIP-600.

what i feel that the SIP-600 will be end of sale in the coming years,please correct me if i am wrong.unless there is main differnce between SIP-601 and SIP-600



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