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Community Member

Internet speed problem

I am using a 3825 as an edge router. It has only the two integrated gig ports hard set to 100/full. On my side is a 6509 (hard set to 100/full)and on the ISP side is a Riverstone 10/100 switch (set to 100/full). I can only drive the throughput to about 2000pps at about 10Mbs (combined both in/out). Once in a while I see spikes over 10Mbs.

I noticed that my 6509 doesn't support flow control on the 100BaseT ports but the 3825 says flow control is set to XON. I can't find any command to change this. Could this be a problem?

Community Member

Re: Internet speed problem


Cisco 6509 switch if the switch running with CatOS then you can do the flow control by changing the port speed.



Community Member

Re: Internet speed problem

??? I am running hybrid os but the "set port speed" command has no options for flow control that I can see.

When I do a "set port flowcontrol" command I get "flowcontrol mode 'on' not supported on module"

Community Member

Re: Internet speed problem

How are you testing pps? What size packets are you using?

Testing throughput or bandwidth using any kind of TCP/IP transfer will not be accuarate due to varying packet sizes, acknowledgements, and other TCP overhead.

Community Member

Re: Internet speed problem

PPS is just by the counters on the interface. I am not tracking sizes. Bandwidth utilization is monitored by MRTG and flattens out at 10Mbs with spikes up to about 18Mbs.

Community Member

Re: Internet speed problem

Please Check 3825 interface config:

interface GigabitEthernet0/0

duplex full

speed 100

media-type rj45

negotiation auto

Community Member

Re: Internet speed problem

interface GigabitEthernet0/0

description $ETH-LAN$$FW_INSIDE$

ip address

no ip redirects

no ip unreachables

no ip proxy-arp

ip nat inside

ip route-cache flow

load-interval 30

duplex full

speed 100

media-type rj45

no cdp enable

no mop enabled

hold-queue 2500 in

hold-queue 200 out


Re: Internet speed problem

The config. looks fine. Did you confirm the ISP did not limit the throughput and find any packet when it reach 10M or 18Mbps ? Please provide the "sh int".


Re: Internet speed problem

Sorry. I mean do yuo find any packet drop when it reach 10Mbps or 18Mbps.

Community Member

Re: Internet speed problem

I am working with the ISP right now. I am just trying to rule out anything on my side. I noticed the flow control thing (see my first post) and didn't know if that would affect throughput.

Thanks for all the responses!

GigabitEthernet0/0 is up, line protocol is up

Hardware is BCM1125 Internal MAC, address is 0012.7f29.04c0 (bia 0012.7f29.04


Description: $ETH-LAN$$FW_INSIDE$

Internet address is

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 11/255, rxload 2/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, link type is autonegotiation, media type is RJ45

output flow-control is XON, input flow-control is XON

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 2w4d

Input queue: 0/2500/0/86 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/200 (size/max)

30 second input rate 1078000 bits/sec, 502 packets/sec

30 second output rate 4419000 bits/sec, 612 packets/sec

553006601 packets input, 3478560860 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 940490 multicast, 0 pause input

0 input packets with dribble condition detected

690657734 packets output, 1645866688 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 pause output

0 output buffer failures, 0 output buffers swapped out


Re: Internet speed problem

I don't find any problem of the interface. There is only one issue that the config. show it is manual config. of speed/duplex but it is auto from the sh int. Can you clarify it is manual setup ?

There is no packet drop at the interface, will the limitation is carried on the end device, e.g. your LAN side or the remote side behind the ISP ?

I suggest to disconnect the GE from the ISP and try to connect the GE to a PC then make a throughput test locally. If there is no problem, it is the ISP issue or the remote end host issue.

Hope this helps.

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