[mrtg] Re: CableModem Interfaces
colman at ppllc.com
Wed Jun 8 16:32:15 MEST 2005
Thanks for the detailed explanation. The way you explained it does seem to
match up with the graphs I am seeing.
1) IF3 and IF4 just seem to be splitting up the data that I can also see on
IF1. Is that correct or am I missing some subtelty as to whay it is split
2) IF1 is the same data, just in reverse, of what I am seeing on the server's
eth0. Again, is that correct or am I missing something?
3) If the above are correct, if I want to graph my internet traffic, all I
really need to grapg is my server's eth0. I don't see any value-added to
graphing the interfaces on the cablemode. Is this correct too?
>>>>> "CAC" == Christopher A Congdon <ccongdon at congdonweb.com> writes:
CAC> I don't know the ins and outs of cable modems in general, but it
CAC> seems to me that what you *should* see if this thing adheres to
CAC> certain standards...
CAC> Interface 1) You should see inbound and outbound traffic. Inbound
CAC> should represent the traffic you are sending from your network to the
CAC> 'net. Outbound should represent traffic your modem is receiving from
CAC> the 'net and being transmitted to your network.
CAC> Interface 2) This is probably some sort of 'internal' interface. Many
CAC> devices have if's like this and can be ignored.
CAC> Interface 3/4) You may want to look into combining these two
CAC> interfaces as the same graph. I'm not sure why they are separately
CAC> listed interfaces, but IF3 should be your Internet to LAN traffic and
CAC> IF4 should be your LAN to Internet traffic.
CAC> Interface 5) This would be the traffic you would see if you had a USB
CAC> cable hooked up to your cable modem. If you're not using USB, you can
CAC> comment out this IF.
CAC> If your server is doing most of the Internet traffic on your network,
CAC> it is no surprise that the IF3 matches your server's inbound
CAC> traffic. Since your server is pulling packets from the 'Net, they
CAC> have to follow through the inbound interface on your Cable Modem,
CAC> which is IF3. You should see a matching graph of Outbound Traffic
CAC> color on the Cable's IF1. This also means that your server's ETH0
CAC> outbound should be a close match for the cable's IF4.
CAC> Judging by the Configmaker interfaces, it is no surprise that IF4
CAC> only shows outbound traffic. IF1 however should show inbound and
CAC> outbound...after all, it should be a standard Ethernet interface.
CAC> Again, your best bet is to have MRTG make two graphs for you, one
CAC> showing inbound and outbound for the cable's IF1, and a combo graph
CAC> showing IF3 as inbound and IF4 as outbound traffic.
>> -----Original Message-----
>> From: mrtg-bounce at list.ee.ethz.ch [mailto:mrtg-bounce at list.ee.ethz.ch]
>> Behalf Of Jake Colman
>> Sent: Tuesday, June 07, 2005 09:00
>> To: mrtg at list.ee.ethz.ch
>> Subject: [mrtg] CableModem Interfaces
>> I have a cablemodem connected to eth0; eth1 is used for the internal
>> network. I used cfgmaker to create a config for eth0 and for the
>> on the cablemodem (a docsis-compatible SB5100).
>> I don't understand what the various cablemodem interfaces mean nor do
>> understand how I can use these interfaces to graph the bandwidth I am
>> when connected to the internet.
>> cfgmaker found 4 interfaces on the SB5100:
>> 1) ifType: ethernetCsmacd (6); ifName: eth0
>> 2) skipped
>> 3) ifType: CATV Downstream Interface (128); ifname: <none>
>> 4) ifType: CATV Upstream Interface (129); ifname: <none>
>> 5) ifType: (160); ifName: usb0
>> The downstream interface (interface 3) seems to have exactly the same
>> for incoming bytes as that shown for my server's eth0 interface.
>> Interfaces 1 and 4 show only outbound bytes but I have no idea what
>> represents. Can anyone explain?
>> Ultimately, what I'd like to graph is the amount of my available
>> that I am currently consuming in both directions. Any suggestions how
>> Jake Colman
>> Sr. Applications Developer
>> Principia Partners LLC
>> Harborside Financial Center
>> 1001 Plaza Two
>> Jersey City, NJ 07311
>> (201) 209-2467
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Sr. Applications Developer
Principia Partners LLC
Harborside Financial Center
1001 Plaza Two
Jersey City, NJ 07311
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