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New Member

Traffic through router

Hi

We have a3640 router with two 100 fastethernet connections. Currently the usage on fe 0/0 is very high average is 95mbit/s. We have a server that is running backups, what I'd like to know is why doesn't the server soak up the remaining bandwidth? Is there something inherent with ethernet that prevents usage up 100mbit/s or is there something I need to do on the router?

Thanks in advance

Dan

4 REPLIES

Re: Traffic through router

You should best replace the router. To my best knowledge, the 3640 does not route 100Mb/s at wire speed. To confirm this, check the cpu load on the router (sh proc). If this is approaching the 100% mark you know how things are.

To make sure that you are getting the maximum out of your router, make sure that fast switching is ON. This can be verified by looking at the interface config:

sh ip int e1/0

Ethernet1/0 is up, line protocol is up

Internet address is 129.1.2.32/24

Broadcast address is 255.255.255.255

Address determined by non-volatile memory

MTU is 1500 bytes

Helper address is not set

Directed broadcast forwarding is disabled

... ...

Look for the following line:

IP fast switching is enabled <<< This one!!

Use the interface command: ip route-cache to activate Fast Switching if it is disabled.

Regards,

Leo

New Member

Re: Traffic through router

Hi

Thanks for your reply. I've check and fast switching is enabled. Additionally here's the top part of "show proc"

CPU utilization for five seconds: 61%/60%; one minute: 63%; five minutes: 61%

PID QTy PC Runtime (ms) Invoked uSecs Stacks TTY Process

1 Csp 60381EB8 14108 3038618 4 2600/3000 0 Load Meter

2 ME 605F1FAC 2930248 11145535 262 7532/9000 0 OSPF Hello

3 Lst 60369A50 10126184 1731651 5847 5632/6000 0 Check heaps

4 Cwe 60361248 0 1 0 5572/6000 0 Chunk Manager

I'm not great with understanding the above, any chance you can enlighten me into what it means?

Regards

Dan

Re: Traffic through router

Best answer this with a link:

http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00801a8b10.html

Your processor is 61% busy on average over the last 5 mins. Relate this to the actual througput. Then (for simplicity) assume a linear increase of througput and CPU-load. This will result in an estimate of your router's ultimate performance. Keep in mind that the 3600 platform originally dates from the times when 10Mb was the standard for a WAN interface. The performance was simply not designed for a 10-fold increase of that figure. This is one of the reasons why it was replaced some 8-10 years ago.

Regards,

Leo

Re: Traffic through router

Hi Dan,

Kindly let us know from where you are referring that the bandwidth utilisation is touching 95mbps.

Are you referring to any bandwidth utilisation graphs or from the show interface statistics.

If it was from "show interface statistics", what is the load interval configured on the interface. Can kindly paste the output here to examine. 300 seconds is the default load interval. Hence with this configuration, the statistics that you are observing by the show interface output, is the average data for the past 300 seconds. As you are seeing only the average figure here, it will not reflect the exact current utilisation.

You can reduce the load-interval down to 30 seconds to get much better statistics.

URL to refer

************

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_command_reference_chapter09186a00800d983d.html#wp1018413

However we should keep in mind that again this will just be a moving average for the 30 second window. We can never estimate the actual utilisation exact down to the second. Thats how bandwidth monitoring works.

What is the protocol nature of the traffic generated by your server. If it is for backup purpose, then i assume it would be based on TCP.

One point to consider here is that for a given TCP data transfer window, we can never see a link getting utilised full. It is due to the sliding window nature of TCP.

Hence with just one data transfer we cannot witness the intermediate link getting fully utilised.

Probably you can generate more traffic to pass through that link to witness the near/full utilisation of that fastethernet link.

Hope this helps. Kindly rate the post if it does.

-VJ

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