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shirishag75 01-27-2009 01:56 PM

wired link between router and ethernet card
Hi all,
I wanna know is there a way to know the speed between the ethernet card and router. Specifically if the router is limited to 10 Mbps or something (speed)

Speed of ethernet card is 10/100 Mbps depending on the other side of the link .


$ sudo ethtool eth1
[sudo] password for shirish:
Settings for eth1:
    Supported ports: [ TP MII ]
    Supported link modes:  10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
    Supports auto-negotiation: Yes
    Advertised link modes:  10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
    Advertised auto-negotiation: Yes
    Speed: 100Mb/s
    Duplex: Full
    Port: MII
    PHYAD: 32
    Transceiver: internal
    Auto-negotiation: on
    Supports Wake-on: pumbg
    Wake-on: d
    Current message level: 0x00000007 (7)
    Link detected: yes

Another way


$ sudo mii-tool -v eth1
eth1: negotiated 100baseTx-FD, link ok
  product info: vendor 00:00:00, model 0 rev 0
  basic mode:  autonegotiation enabled
  basic status: autonegotiation complete, link ok
  capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  advertising:  100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD


$ sudo tcpdump -s0 -i eth1 -w output.cap host
tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes

From the above it can be seen it seems to be auto-negotiated at 10 Mbps.

Am I reading it right or wrong?

If there is someway to explicitly know what speed is the router able to transfer data between itself and the ethernet card (apart from the derived logic)

acid_kewpie 01-27-2009 02:05 PM

why do you think it's 10? ethtool and mii-tool both clearly state it's 100...

"able to" is a vague thing... you will naturally never get 100mbps in reality, but 80mbps should be realistic assuming it's a direct link with no other machines switching across that layer 2 path. what really matters is what data you actually have to transfer in the first place. If you have enough data to shift between the two points then you can just see for yourself using all manner of tools, like iptraf.

jlinkels 01-27-2009 07:01 PM

I know the speed of my ethernet link is higher than 10 Mbit, but tcpdump gives the same spec of EN10MB.

With modern interfaces it is unikely you are stuck at 10 Mb. Many switches have an indicator whether the link is 10/100 Mb and full/half duplex.

You can also do

dmesg | grep 100M[Bb]
This output I get:

eth0: link up, 100Mbps, full-duplex, lpa 0x45E1

shirishag75 01-27-2009 09:26 PM

I got the following output :-


$ dmesg | grep 100M[Bb]
[  36.358158] eth1: link up, 100Mbps, full-duplex, lpa 0x41E1
[32810.174414] eth1: link up, 100Mbps, full-duplex, lpa 0x41E1
[32820.137062] eth1: link up, 100Mbps, full-duplex, lpa 0x41E1

Jinkels or anybody for that matter, what does the [Bb] stand for?

acid_kewpie 01-28-2009 04:15 AM

it just matches MB or Mb

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