I have a public facing Internet router on a 2Mb cicuit. I would like to restrict the amount of bandwidth used by SMTP only, but leave all other traffic as is.
I believe this is possible, but not sure of the commands, I would like to say restrict SMTP inbound/outbound to 256k, can anyone help ?
rate-limit will do this for you, you just have to define an ACL to catch all the traffic you want (eg port 25). Mail back if you need further help.
Regards Paul
You would probably be better off using QoS to do this instead of rate-limiting. For example, if you wanted SMTP to use no more than 256k when the pipe is 80% loaded, but use as much as it can when the pipe is less than 80% utilized, than QoS is the way to go. Rate-limiting is easier to configure, but QoS is better because rate-limiting will drop the packets that exceed the threshold, while QoS will queue the packets, and only drop packets when the queues get full.
In article , thrill5 wrote: :You would probably be better off using QoS to do this instead of :rate-limiting. For example, if you wanted SMTP to use no more than 256k :when the pipe is 80% loaded, but use as much as it can when the pipe is :less than 80% utilized, than QoS is the way to go. Rate-limiting is easier :to configure, but QoS is better because rate-limiting will drop the packets :that exceed the threshold, while QoS will queue the packets, and only drop :packets when the queues get full.
QoS is a policy framework, and rate-limiting is one of the possible policy-enforcement mechanisms that can be applied within QoS. Thus one should not speak of using QoS -instead- of rate-limiting. One could, though, speak of using rate-shaping instead of rate-limiting .
Yes I agree, CBWFQ would seem to be a better policy for this sort of thing.
Thanks guys for replying. Can either of these methods be configured with standard IOS on a Cisco 2600 router ??
Sorry I'm not 100% sure. Try the below on yours and see if you get the command "rate-limit" come up. CBWFQ (class based weighted fair queuing) is a little more complex to setup so I would suggest trying the rate-limit option first and if it works maybe look at 'upgrading' to CBWFQ.
c2600#conf t Enter configuration commands, one per line. End with CNTL/Z. c2600(config)#int eth0/0 c2600(config-if)#rate? rate-limit
I've included below a sample config that I *think* should do the trick, what it does is limit any traffic going into or out of the ethernet port destined for port 25 to 256k.
access-list 120 permit tcp any any eq 25
interface Ethernet0/0 rate-limit input access-group 120 256000 2000 2000 conform-action transmit exceed-action drop rate-limit output access-group 120 256000 2000 2000 conform-action transmit exceed-action drop
Regards, Paul
It did take me a while to get CBWFQ sorted out but it is easy to follow the config. I am not clear why it was quite confusing, stupidity I guess.
Search for PM-voice-out in this list to find a working example. It though did not need access lists so you would have to add that yourself.
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