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intevlan routing help

saidrossaidros Member Posts: 4 ■□□□□□□□□□
in CCNA & CCENT
hi everyone i hope you can help me out here

i have this configuration

Core switch (svi for vlans, 5,6,7,8,9,10 and management 1)
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trunk passing vlans 5,6,7,8,9,10,1
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Switch 3 (vlans 9 and 10) and svi for vlan 1
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trunk passing vlans 5,6,7,8 and 1
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switch2 (Vlans 7 and icon_cool.gif and svi for vlan 1
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trunk passing vlans 5,6 and 1
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switch1 (vlans 5 and 6) and svi for vlan 1


i say this wont work for all users on all vlans be able to communicate between them, but my boss says it will and i have a window next week so i just want to verify im not confussed, please help me out thanks
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    EdTheLadEdTheLad Member Posts: 2,111 ■■■■□□□□□□
    It wont work, for a start you need all vlans configured on switches 1,2 and 3 otherwise the switches will not associate the incoming unknown tags to the outgoing trunks.For users in different vlans to communicate you will need a L3 switch or router.
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
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    ncsugrad2002ncsugrad2002 Member Posts: 131
    What type of equipment are you using?

    And ^ is correct. nvm
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    saidrossaidros Member Posts: 4 ■□□□□□□□□□
    EdTheLad wrote: »
    It wont work, for a start you need all vlans configured on switches 1,2 and 3 otherwise the switches will not associate the incoming unknown tags to the outgoing trunks.For users in different vlans to communicate you will need a L3 switch or router.


    Yeah all vlans on all the switches and on the trunks, they have all of this switches are 3750 but acting s L2 switches and the switch Core is the one with al svi for the intervlan routing, thanks for clarifying this for me.
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    kryollakryolla Member Posts: 785
    Your boss is right it should work. You dont have the same vlan spread across all switches so you dont need a trunk to have all vlans. If vlan 5 need to talk to vlan 7 it will travel upstream and all trunks upstream has vlan 5 to the core switch which is the default gateway for vlan 5 and will route it to vlan 7 then travel downstream to sw 2 and all trunks in between the core switch and sw2 has vlan 7. Hope this makes sense
    Studying for CCIE and drinking Home Brew
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    saidrossaidros Member Posts: 4 ■□□□□□□□□□
    kryolla wrote: »
    Your boss is right it should work. You dont have the same vlan spread across all switches so you dont need a trunk to have all vlans. If vlan 5 need to talk to vlan 7 it will travel upstream and all trunks upstream has vlan 5 to the core switch which is the default gateway for vlan 5 and will route it to vlan 7 then travel downstream to sw 2 and all trunks in between the core switch and sw2 has vlan 7. Hope this makes sense


    hmmm that actually sounds about right.
    And if vlan 7 wants to talk with vlan 5 it goes up and then down to sw1, that means i dont have to have all vlans configured in all switches just need to let it pass on the trunk and should work right?, which matches the configuration i have here. Nice

    I appreciate the help
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    networker050184networker050184 Mod Posts: 11,962 Mod
    saidros wrote: »
    hmmm that actually sounds about right.
    And if vlan 7 wants to talk with vlan 5 it goes up and then down to sw1, that means i dont have to have all vlans configured in all switches just need to let it pass on the trunk and should work right?, which matches the configuration i have here. Nice

    I appreciate the help

    If a switch does not have a VLAN configured it will not pass it on its trunks. So as long as each switch has all the VLANs in its VLAN database it should be good to go.
    An expert is a man who has made all the mistakes which can be made.
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    kryollakryolla Member Posts: 785
    sw1 only needs vlan1, 5 & 6 in vlan database
    sw2 only needs vlan1, 5, 6, 7, & 8 in vlan database
    sw3 only needs vlan1, 5, 6, 7, 8, 9, & 10 in vlan database
    Studying for CCIE and drinking Home Brew
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    eduromereduromer Member Posts: 63 ■■□□□□□□□□
    saidros wrote: »
    hmmm that actually sounds about right.
    And if vlan 7 wants to talk with vlan 5 it goes up and then down to sw1, that means i dont have to have all vlans configured in all switches just need to let it pass on the trunk and should work right?, which matches the configuration i have here. Nice

    I appreciate the help


    kryolla is right you dont need to have all vlans in all the switches, only the core the one where you have all the svi need to have them, i just tested it on the lab so it works =) hope this helps
    "Almost..... is as good as Nothing"
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    networker050184networker050184 Mod Posts: 11,962 Mod
    If all switches are connected to the core switch then you will only need the VLANs that are used locally. If they are all connected in a daisy chain like the drawing you will need the VLANs on all the switches. If switch 3 receives a frame tagged with VLAN 5 on its trunk it will drop it if it doesn't know about that VLAN.
    An expert is a man who has made all the mistakes which can be made.
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    kryollakryolla Member Posts: 785
    networker050184 wrote: »
    If all switches are connected to the core switch then you will only need the VLANs that are used locally. If they are all connected in a daisy chain like the drawing you will need the VLANs on all the switches. If switch 3 receives a frame tagged with VLAN 5 on its trunk it will drop it if it doesn't know about that VLAN.

    no you dont you only need what I said in an earlier post and eduromer proved it
    Studying for CCIE and drinking Home Brew
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    networker050184networker050184 Mod Posts: 11,962 Mod
    Well I just labbed it up also and it did not work how you said it. The only way I got it to work was to add the VLAN to all the switches. If you don't believe me you can lab it too.
    An expert is a man who has made all the mistakes which can be made.
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    kryollakryolla Member Posts: 785
    networker050184 wrote: »
    Well I just labbed it up also and it did not work how you said it. The only way I got it to work was to add the VLAN to all the switches. If you don't believe me you can lab it too.

    well you configured your lab wrong LOL why does SW1 need all the other vlans configured when it does have any users ON or downstream from it same goes for SW2?
    Studying for CCIE and drinking Home Brew
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    networker050184networker050184 Mod Posts: 11,962 Mod
    kryolla wrote: »
    well you configured your lab wrong LOL why does SW1 need all the other vlans configured when it does have any users ON or downstream from it same goes for SW2?

    You need the VLANs in the transit path. If switch 3 only has VLANs 9 and 10 in its VLAN databas then it will drop the frames tagged VLAN 5 when it receives it on a trunk.

    EDIT: I got what what you are saying now. I missed that your VLAN list had the lower VLANs in it.
    An expert is a man who has made all the mistakes which can be made.
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    kryollakryolla Member Posts: 785
    networker050184 wrote: »
    You need the VLANs in the transit path. If switch 3 only has VLANs 9 and 10 in its VLAN databas then it will drop the frames tagged VLAN 5 when it receives it on a trunk.

    EDIT: I got what what you are saying now. I missed that your VLAN list had the lower VLANs in it.

    :) Now you see why you dont need all vlans in all switches
    Studying for CCIE and drinking Home Brew
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    networker050184networker050184 Mod Posts: 11,962 Mod
    kryolla wrote: »
    :) Now you see why you dont need all vlans in all switches


    Yeah, read your post too fast. His drawing is switch 3-2-1 you list is 1-2-3. I was thinking how the hell is switch 3 going to pass the traffic for all the VLANs with only two VLANs!
    An expert is a man who has made all the mistakes which can be made.
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    eduromereduromer Member Posts: 63 ■■□□□□□□□□
    networker050184 wrote: »
    Yeah, read your post too fast. His drawing is switch 3-2-1 you list is 1-2-3. I was thinking how the hell is switch 3 going to pass the traffic for all the VLANs with only two VLANs!

    see my lab was right lol i did again cause you made me doubt ;) but yeah glad we all could agree
    "Almost..... is as good as Nothing"
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    saidrossaidros Member Posts: 4 ■□□□□□□□□□
    Thank you to all of you :) glad you could help me out and explain it to me thanx you guys
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