What are eth0 and vlan0

Discussion in 'Tomato Firmware' started by CheapScotsman, Feb 21, 2007.

  1. CheapScotsman

    CheapScotsman LI Guru Member

    Tomato 1.04.0944 on a WRT54GL Version 1.1

    I’ve been through the wiki at (http://en.wikibooks.org/wiki/Tomato_Firmware)i and searched the forums here and, perhaps just a tad confused and while this (http://www.linksysinfo.org/forums/showthread.php?p=290668) help I am looking for a more definitive tomato answer:

    In Status/Device List it lists the interfaces as vlan1, eth1 and br0

    But in the Bandwidth/Real Time, it has vlan1, eth1 and br0 … but it also has eth0 and vlan0 … what are these?

    Thanks in advance
  2. der_Kief

    der_Kief Super Moderator Staff Member Member

    Hi CheapScotsman,

    as the WRT54GL is the same as a WRT54Gv4 maybe the following graphic will help you.

  3. Myriddin

    Myriddin LI Guru Member

    Hi Der Kief,

    your schema help me to understand how it work, but:

    it's correct to say that ALL the traffic goes through the br0 interface?


    All the traffic goes through the br0 with the exclusion of Vlan0 internal traffic (ex: local PC to my xbox in my network?

    I would like to understand because i understand that the QoS is applied to Br0 so if i decide to limit the connection number i wouldn't like to have as side effect a limitation on vlan0 in term of total numeber of connection allowed.
  4. CheapScotsman

    CheapScotsman LI Guru Member

    Thanks for the picture it really helps but a leave a few questions

    The wiki indicates that "br0 refers to Wired Ethernet (LAN) devices. In other words, devices that are connected to the router on the four Ethernet ports (either directly or via a hub or switch)" but in the diagram above it appears that BR0 connects eth1 to vlan0

    The wiki defition seems appropriate give that hard wired connections show up in the device list AND that i am getting traffic stats on BR0 from my one computer and I have no wireless devices attached


    If BR0 is the wired ethernet then how it it different than vlan0? ... the stats are a almost the same but maybe vlan0 would include eth1? maybe I need to add in some wireless and test it?

    From the picture, if eth0 is the connection between the CPU and the switch then vlan1+vlan0 should add up to eth0. From my 5 hour bandwidth, inbound only averages ....

    vlan1 is 34.89, vlan0 is .73 for a total of 35.62 while eth0 is 48.02 ... Where did the remaining 13 go?
  5. ericren23

    ericren23 LI Guru Member

    Im using tomato 1.07 on WRT54GL and I also have this happening on my network

    Taking my last 10hr of bandwidth i get the following:

    RX 354.17 MB
    TX 243.68 MB

    RX 133.14
    TX 56.12

    RX 238.46
    TX 261.82

    RX 514.8
    TX 451.96

    RX 110.28
    TX 208.34

    Now the TX values of vlan0 + vlan1 = eth0
    but taking the RX values vlan0(110) + vlan1(354) = 464 which is NOT the RX of eth0

    Also, is it correct to say that vlan0 + eth1 = br0? The values almost adds right.

    Can someone take theses values and tell us exactly how they relate?

  6. Bill_MI

    Bill_MI Network Guru Member

    Let me try, even though I've only been looking at this for a year. The confusion is the combination of physical and virtual things.

    etho (ALL the LAN/WAN ports) and eth1 (WIFI only) are the PHYSICAL interfaces. Much like network cards dumbed down. They are real hardware ports to the processor.

    Now, notice those switches have a "tagging". This is how the low-level kernel sorts out what data came from what ethernet switch over eth0. Where does it sort this data to? They go into the *virtual* creations of vlan0 (lan) and vlan1 (wan). Tagging is data put on (by the hardware) for identification and common in multi-port switches like this.

    And yes... eth0 data is BOTH lan and wan data when setup like most are. The magic of tagging is all that eventually separates them. You may already be aware the 5 ports can be configured many ways including the 4-lan, 1-wan standard.

    Don't get confused - a "vlan" doesn't mean "LAN". It should probably have been called "vnet" (virtual network) to avoid the confusion. Notice "vlan1" is the "WAN".

    Now enter a BRIDGE (br0). This combines vlan0 and the wifi (eth1) data into one bridged entity you know as... well... a more complete LAN I guess. :) It has the ethernet switches AND wifi combined.

    So why a bridge and not another vlan? I think because these two things (vlan0 and eth1) are complete interfaces so need the specifics of a bridge to resolve their data flow. Someone with more insight can clarify this.

    And yes, if you graph or log data from each of these it should match this model. In fact, eth0 should get double the data on an internet exchange since it'll have both the lan and wan side of things.

    This stuff is internal to all routers to a great extent - especially the tagging to use one giant 5-port switch as 4-lans and 1-wan.

    Hope I helped. And gee... I didn't realize this was an old thread. :)
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