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Budget Router With High Throughput?

Daniel Mckibbin

I have a 3640a, 3550 and airopoint 350 I use for my home internet connection. I know it's old equipment, but it's all I could afford at the time. Directly plugged into my modem I get about 10 mb/s, plugged into a switch port no greater than 6, and about 5-6 when connected to wireless which is understandable because it's only wireless B. I'm going to downgrade my connection for the time being as I'm paying for excess bandwidth that I'm unable to use, but I was wondering if anyone knows of any more recent, affordable cisco routers that can handle a high speed cable connection? What kind of throughput does the 3550 get? Cisco states a throughput of approximately 45-60mb/s for the 3640a, don't know where they get that figure though as I can't get above 6 megs.

14 Replies 14

paolo bevilacqua
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If you have ADSL, you should get an 857. Add W to P/N you can also eliminate the external AP.

Rising star
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First of all your 3640a should be able to do more than that so there is most likely a problem with the config somewhere eating resources or something like that.

you seem to be interested in cisco equipment and how to use cisco equipment so I would recomend e-bay.

loads of "old" routers and equipment that can be helpful to do testing and gain knowledge  and experience.

Good luck


I'm not very interested in a integrated services router as they don't support near as many features as Cisco Enterprise routers. I'm just looking for a router that I know I can get good throughput. I did some load testing today. With WAN killer it was getting 40 megs receive, but it was getting fragment table overloads every second, and the router was unresponsive. I did a 8 gig file transfer between hosts between 2 vlans so the router would be involved in forwarding traffic and I was only getting about 7 megs in both direction with the CPU pegged. It seems the CPU is the limiting factor of this router. It is only 100 mhz:

Processor board ID 30050642
R4700 CPU at 100MHz, Implementation 33, Rev 1.0

  5 minute input rate 7373000 bits/sec, 2019 packets/sec
  5 minute output rate 7327000 bits/sec, 2019 packets/sec

CPU utilization for five seconds: 99%/95%; one minute: 99%; five minutes: 86%
PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
   2       59200      3609      16403  0.08%  0.06%  0.06%   0 Load Meter
   3       51792       502     103171  0.08%  0.12%  0.08%   0 Exec
  16      145236     39809       3648  0.16%  0.12%  0.14%   0 ARP Input
  31       24640     17856       1379  0.08%  0.07%  0.07%   0 Per-Second Jobs
  76       14840     69381        213  0.08%  0.04%  0.04%   0 SSS Feature Time
  92       25276    173448        145  0.08%  0.06%  0.07%   0 RBSCP Background
170      130124      2562      50790  0.41%  0.61%  0.53%   0 crypto sw pk pro
182       98200   4048621         24  0.16%  0.22%  0.62%   0 IP SLA Mon Event
  5 minute input rate 10126000 bits/sec, 2924 packets/sec
  5 minute output rate 9234000 bits/sec, 2801 packets/sec
     1485994 packets input, 622453988 bytes

Next I did the same transfer between hosts within the same vlan so the router wouldn't be involved and the results are much much better. 36 megs, with all traffic being forwarded in hardware:

5 minute input rate 2908000 bits/sec, 5578 packets/sec
  5 minute output rate 36255000 bits/sec, 5245 packets/sec

CPU utilization for five seconds: 0%/0%; one minute: 0%; five minutes: 0%

I was wondering if there would be a significantly difference between performance with router on a stick and enabling layer 3 on the 3550 and running a routing protocol between it and the router? It seems the switch has good performance and I just need a router that can keep up. Any suggestions?

Daniel.Mckibbin1 wrote:

I'm not very interested in a integrated services router as they don't support near as many features as Cisco Enterprise routers. I'm just looking for a router that I know I can get good throughput.

Excuse me, what are you talking about? Ther routers I have  indicated above are right ones for the job and they do everything. Only, the 851 has some Sw limitations.

The 3640 you're using may have buggy software or be configured incorrectly, from that the performance issue.

My appologies if I offended, but looking at Cisco's description of the router it only supports ripv1 and v2. If those are the only routing protocols it supports then I'm sure there are other features it is lacking as well. Not to mention it only has 64 megs of RAM, half of what my 3640 has.

No offence but please be more trusttful of seniors in this trade.

I don't know where you're looking but the ISRs router supports all routing protocols and some more. By the way, with which other devices you would use routing protocols ?

Also memory is not a concern as I doubt you'll be running some tens of thousand subnets or VPNs etc.

I was looking at Cisco's description of the router, but I guess that's the generic bundled IOS that can be upgraded. I kind of want to get a router that I can not only use for my home connection, but in conjunction with my lab as well, which is why I'm so hung up about features. I'm going to try a different IOS on my 3640a as it should be able to do more than it's doing.

I loaded a older IOS version with similar results. I'm beginning to think it's the router itself. In the case of the file transfer it was 6 megs transmit and receive, total 12 megs. Maybe that is the max that this router can handle? I see nothing wrong with the config, but you can take a look if you want. I see no errors on the interface either.

I'm thinking I may set up SVI's on the 3550 for intervlan traffic and set up a routing protocol between the two, becuase the switch seems to have more tolerance for a high amount of traffic and I can prevent those broadcasts and intervlan traffic from traversing the router, hopefully freeing up resources for internet traffic. What are your thoughts? For now I don't have the funds for a new router, but I'm still looking into possibilites including the soho router you suggested, maybe an 1811..

Might I ask what cards you have installed on the router ?

The router itself have a theoretical limit of 50-70Kpps.


Do you mean 50-70 Mb/s or is that in packets per second? Because after about 6,000 packets per second it really hangs up. The following is a list of the cards installed:

NAME: "One port Fastethernet TX", DESCR: "One port Fastethernet TX"
PID: NM-1FE-TX=        , VID: 1.1, SN: 28849491

NAME: "Ethernet/WAN", DESCR: "Ethernet/WAN"
PID: NM-2E2W=          , VID: 1.2, SN: 10223931

NAME: "FastEthernet/Token Ring/WAN", DESCR: "FastEthernet/Token Ring/WAN"
PID: NM-1FE1R2W=       , VID: 1.0, SN: JAD04410H3O

NAME: "Four Port High-Speed Serial", DESCR: "Four Port High-Speed Serial"
PID: NM-4T=            , VID: 1.1, SN: 27290930

However, I'm only using the two Fast ethernet ports. One for the Internet connection, and one for the trunk between the router and switch.

No I did mean 50 000 - 70 000 packets per second.

to know what your router can do you need to know the number of packets per second your router can handle, but also the size of that packet.

a normal ethernet packet (lets leave jumbo frames and so on out of this for now atleast) has a size between 64 and roughly 1500 bits.

as a general rule it takes as long to process a 64 bit frame as it does a 1500 bit frame.

to calculate the bandwith you would need to calculate 50 000 (packets processed per second) X 64 (bits in the packet) X 8 (byte -> bit) = 25 600 000 so the router does minimum 25,6 mbit

so why does yours only do 12 ? and during a file transfer most of the packets should be somewhere around 1500 bytes. wich would give a lot higher values.

so this makes no sense. something somewhere is not as it should be. either your testing is off or your router have a configuration /software /hardware error in it. are you doing fx NAT and such things ?

start with removing the cards that are not used.

reser the router to the simples configuration two ip on two interfaces route between them only and retest.

Good luck


Can you do the command below on your 3640a

sh ip cef

is that up and running ?

here is a link to more information

Good luck


Yep CEF is up and running Globally. I have attempted to use an older IOS revision, different configs and interfaces with the same results. I was thinking of trying fast switching see if for some reason it gives me a performance boost. I doubt it.

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