cisco vlan routing question

Discussion in 'Cisco' started by David K, Nov 26, 2003.

  1. David K

    David K Guest

    in class today we connected 2 cisco switches toghter with 2 host on each
    switch
    each host on each side was in vlan 2 and vlan 3.
    both vlans in there own subnet
    we configured a trunking port to connect each of them
    all worked fine for the host in the vlans talking to the host in the same
    vlan on the other switch
    then we tried to put a router in between the switches
    it was a 2600 with 2 ethernet interfaces
    we tried to set it up but we could not figure out how to do in ip addressing
    on the router
    we came to the conslusion that it cant be done like this because
    you cant assign the same network subnet to more than one interface.
    is there some other way we could have done this??

    -dk
     
    David K, Nov 26, 2003
    #1
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  2. David K

    Salus Guest

    ..Q and ISL trunking available on the router IOS?

    Salus
     
    Salus, Nov 26, 2003
    #2
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  3. David K

    FireSword Guest

    Of course you can do it.

    When you create VLANS, each vlan should be a different subnet if you want to
    route traffic between them. You place one interface of the router on each
    vlan, and assign a valid host address from that vlan's subnet.

    That's it. and if your instructor does'n know that he souldn't be teaching.

    "David K" <> wrote in message
    news:eek:...
    > in class today we connected 2 cisco switches toghter with 2 host on each
    > switch
    > each host on each side was in vlan 2 and vlan 3.
    > both vlans in there own subnet
    > we configured a trunking port to connect each of them
    > all worked fine for the host in the vlans talking to the host in the same
    > vlan on the other switch
    > then we tried to put a router in between the switches
    > it was a 2600 with 2 ethernet interfaces
    > we tried to set it up but we could not figure out how to do in ip

    addressing
    > on the router
    > we came to the conslusion that it cant be done like this because
    > you cant assign the same network subnet to more than one interface.
    > is there some other way we could have done this??
    >
    > -dk
    >
    >
     
    FireSword, Nov 26, 2003
    #3
  4. David K

    David K Guest

    ok i will try it
    it was just me and a couple other students trying to figure this out
    actually
    the rest of the class left
    teach was out doin somethin else

    "FireSword" <> wrote in message
    news:1069860054.938509@rh9cache...
    > Of course you can do it.
    >
    > When you create VLANS, each vlan should be a different subnet if you want

    to
    > route traffic between them. You place one interface of the router on each
    > vlan, and assign a valid host address from that vlan's subnet.
    >
    > That's it. and if your instructor does'n know that he souldn't be

    teaching.
    >
    > "David K" <> wrote in message
    > news:eek:...
    > > in class today we connected 2 cisco switches toghter with 2 host on each
    > > switch
    > > each host on each side was in vlan 2 and vlan 3.
    > > both vlans in there own subnet
    > > we configured a trunking port to connect each of them
    > > all worked fine for the host in the vlans talking to the host in the

    same
    > > vlan on the other switch
    > > then we tried to put a router in between the switches
    > > it was a 2600 with 2 ethernet interfaces
    > > we tried to set it up but we could not figure out how to do in ip

    > addressing
    > > on the router
    > > we came to the conslusion that it cant be done like this because
    > > you cant assign the same network subnet to more than one interface.
    > > is there some other way we could have done this??
    > >
    > > -dk
    > >
    > >

    >
    >
    >
     
    David K, Nov 26, 2003
    #4
  5. David K

    Jeff Specoli Guest

    It almost sounds like you are saying each VLAN has the same IP subnet
    scheme e.g. VLANA=192.168.45.0/24 and VLANB=192.168.45.0/24, in which
    case you are right. You cannot have two interfaces on the router be
    in the same subnet. You would have to have different subnets for the
    router to "route" between them. Remember a router routes between
    different subnets; however, if both VLANS are in the same IP subnet,
    you could set up bridging:

    Router(config)# interface fastethernet 0
    Router(config-if)# bridge-group 1
    Router(config-if)# interface fastethernet 1
    Router(config-if)# bridge-group 1
    Router(config-if)# exit
    Router(config)# bridge 1 protocol ieee

    the configure the switch to put the port that router fasteth0 is
    connected to in VLANA and put the port fasteth1 is connected to in
    VLANB. This will bridge the two ethernet interfaces and basically
    make the two VLANs one flat VLAN.


    If each VLAN is on different subnets, e.g VLANA=192.168.45.0/24 and
    VLANB=192.168.55.0/24 then you can (as a previous poster pointed out):
    1. Assign an IP in VLANA to one of the routers ethernet ports and
    plug it into a switch and assign that switch port to VLANA. Then
    assign the other ethernet port of the router to an IP in VLANB, and
    plug that ethernet port into a switch port and assign that switchport
    to VLANB. The router will route between the VLANS.

    or

    2. Set up a trunk port from one of the switches to the router. On
    the router:

    Router(config)# interface fastethernet 2.1
    Router(config-subif)# encap dot1q 1
    Router(config-subif)# ip address 192.168.45.1 255.255.255.0
    Router(config-subif)# exit
    Router(config)# interface fastethernet 2.2
    Router(config-subif)# encap dot1q 2
    RRouter(config-subif)# ip address 192.168.55.1 255.255.255.0


    or something like that


    -HTH





    "David K" <> wrote in message news:<>...
    > in class today we connected 2 cisco switches toghter with 2 host on each
    > switch
    > each host on each side was in vlan 2 and vlan 3.
    > both vlans in there own subnet
    > we configured a trunking port to connect each of them
    > all worked fine for the host in the vlans talking to the host in the same
    > vlan on the other switch
    > then we tried to put a router in between the switches
    > it was a 2600 with 2 ethernet interfaces
    > we tried to set it up but we could not figure out how to do in ip addressing
    > on the router
    > we came to the conslusion that it cant be done like this because
    > you cant assign the same network subnet to more than one interface.
    > is there some other way we could have done this??
    >
    > -dk
     
    Jeff Specoli, Nov 26, 2003
    #5
  6. David K

    David K Guest

    I find it kind of hard to clearly explain such a techinical configuration
    with text
    but to be more clear
    switch 1 has 2 hosts
    port 1 trunk to router eth port 0
    port 2 host 1 in vlan 2 subnet 10.1.1/24
    port 3 host 2 in vlan 3 subnet 10.2.2/24
    switch 2 has 2 hosts
    port 1 trunk to router eth port 1
    port 2 host 3 in vlan 2 subnet 10.1.1/24
    port 3 host 4 in vlan 3 subnet 10.2.2/24

    the part we could not figure out is
    port 0 and 1 would need to be configed for 10.1.1/24
    and
    port 0 and 1 would also need to be configed for 10.2.2/24

    do we give the routers ports ip address? and if so
    how do they know which port to goto if they
    poth are connected to the same network ?

    i think that we were just going about this in the wrong way.


    "Jeff Specoli" <> wrote in message
    news:...
    > It almost sounds like you are saying each VLAN has the same IP subnet
    > scheme e.g. VLANA=192.168.45.0/24 and VLANB=192.168.45.0/24, in which
    > case you are right. You cannot have two interfaces on the router be
    > in the same subnet. You would have to have different subnets for the
    > router to "route" between them. Remember a router routes between
    > different subnets; however, if both VLANS are in the same IP subnet,
    > you could set up bridging:
    >
    > Router(config)# interface fastethernet 0
    > Router(config-if)# bridge-group 1
    > Router(config-if)# interface fastethernet 1
    > Router(config-if)# bridge-group 1
    > Router(config-if)# exit
    > Router(config)# bridge 1 protocol ieee
    >
    > the configure the switch to put the port that router fasteth0 is
    > connected to in VLANA and put the port fasteth1 is connected to in
    > VLANB. This will bridge the two ethernet interfaces and basically
    > make the two VLANs one flat VLAN.
    >
    >
    > If each VLAN is on different subnets, e.g VLANA=192.168.45.0/24 and
    > VLANB=192.168.55.0/24 then you can (as a previous poster pointed out):
    > 1. Assign an IP in VLANA to one of the routers ethernet ports and
    > plug it into a switch and assign that switch port to VLANA. Then
    > assign the other ethernet port of the router to an IP in VLANB, and
    > plug that ethernet port into a switch port and assign that switchport
    > to VLANB. The router will route between the VLANS.
    >
    > or
    >
    > 2. Set up a trunk port from one of the switches to the router. On
    > the router:
    >
    > Router(config)# interface fastethernet 2.1
    > Router(config-subif)# encap dot1q 1
    > Router(config-subif)# ip address 192.168.45.1 255.255.255.0
    > Router(config-subif)# exit
    > Router(config)# interface fastethernet 2.2
    > Router(config-subif)# encap dot1q 2
    > RRouter(config-subif)# ip address 192.168.55.1 255.255.255.0
    >
    >
    > or something like that
    >
    >
    > -HTH
    >
    >
    >
    >
    >
    > "David K" <> wrote in message

    news:<>...
    > > in class today we connected 2 cisco switches toghter with 2 host on each
    > > switch
    > > each host on each side was in vlan 2 and vlan 3.
    > > both vlans in there own subnet
    > > we configured a trunking port to connect each of them
    > > all worked fine for the host in the vlans talking to the host in the

    same
    > > vlan on the other switch
    > > then we tried to put a router in between the switches
    > > it was a 2600 with 2 ethernet interfaces
    > > we tried to set it up but we could not figure out how to do in ip

    addressing
    > > on the router
    > > we came to the conslusion that it cant be done like this because
    > > you cant assign the same network subnet to more than one interface.
    > > is there some other way we could have done this??
    > >
    > > -dk
     
    David K, Nov 27, 2003
    #6
  7. David K

    FireSword Guest

    When you use 2 router interfaces to route between vlans you do not use a
    trunk to the router.
    You should have 3 switch ports on vlan 2 (mode access), and 3 switch ports
    on vlan 3 (mode acess).
    In vlan 2 you will have 2 hosts AND one of the router interfaces.
    The same for VLAN3.
    Example:

    VLAN 2
    Three Acess Ports
    Port 1 - router eth0 10.1.1.1/24
    Port 2 - host 1 10.1.1.2/24
    Port 3 - host 2 10.1.1.3/24

    VLAN 2
    Three Acess Ports
    Port 1 - router eth1 10.2.2.1/24
    Port 2 - host 1 10.2.2.2/24
    Port 3 - host 2 10.2.2.3/24


    "David K" <> wrote in message
    news:...
    > I find it kind of hard to clearly explain such a techinical configuration
    > with text
    > but to be more clear
    > switch 1 has 2 hosts
    > port 1 trunk to router eth port 0
    > port 2 host 1 in vlan 2 subnet 10.1.1/24
    > port 3 host 2 in vlan 3 subnet 10.2.2/24
    > switch 2 has 2 hosts
    > port 1 trunk to router eth port 1
    > port 2 host 3 in vlan 2 subnet 10.1.1/24
    > port 3 host 4 in vlan 3 subnet 10.2.2/24
    >
    > the part we could not figure out is
    > port 0 and 1 would need to be configed for 10.1.1/24
    > and
    > port 0 and 1 would also need to be configed for 10.2.2/24
    >
    > do we give the routers ports ip address? and if so
    > how do they know which port to goto if they
    > poth are connected to the same network ?
    >
    > i think that we were just going about this in the wrong way.
    >
    >
    > "Jeff Specoli" <> wrote in message
    > news:...
    > > It almost sounds like you are saying each VLAN has the same IP subnet
    > > scheme e.g. VLANA=192.168.45.0/24 and VLANB=192.168.45.0/24, in which
    > > case you are right. You cannot have two interfaces on the router be
    > > in the same subnet. You would have to have different subnets for the
    > > router to "route" between them. Remember a router routes between
    > > different subnets; however, if both VLANS are in the same IP subnet,
    > > you could set up bridging:
    > >
    > > Router(config)# interface fastethernet 0
    > > Router(config-if)# bridge-group 1
    > > Router(config-if)# interface fastethernet 1
    > > Router(config-if)# bridge-group 1
    > > Router(config-if)# exit
    > > Router(config)# bridge 1 protocol ieee
    > >
    > > the configure the switch to put the port that router fasteth0 is
    > > connected to in VLANA and put the port fasteth1 is connected to in
    > > VLANB. This will bridge the two ethernet interfaces and basically
    > > make the two VLANs one flat VLAN.
    > >
    > >
    > > If each VLAN is on different subnets, e.g VLANA=192.168.45.0/24 and
    > > VLANB=192.168.55.0/24 then you can (as a previous poster pointed out):
    > > 1. Assign an IP in VLANA to one of the routers ethernet ports and
    > > plug it into a switch and assign that switch port to VLANA. Then
    > > assign the other ethernet port of the router to an IP in VLANB, and
    > > plug that ethernet port into a switch port and assign that switchport
    > > to VLANB. The router will route between the VLANS.
    > >
    > > or
    > >
    > > 2. Set up a trunk port from one of the switches to the router. On
    > > the router:
    > >
    > > Router(config)# interface fastethernet 2.1
    > > Router(config-subif)# encap dot1q 1
    > > Router(config-subif)# ip address 192.168.45.1 255.255.255.0
    > > Router(config-subif)# exit
    > > Router(config)# interface fastethernet 2.2
    > > Router(config-subif)# encap dot1q 2
    > > RRouter(config-subif)# ip address 192.168.55.1 255.255.255.0
    > >
    > >
    > > or something like that
    > >
    > >
    > > -HTH
    > >
    > >
    > >
    > >
    > >
    > > "David K" <> wrote in message

    > news:<>...
    > > > in class today we connected 2 cisco switches toghter with 2 host on

    each
    > > > switch
    > > > each host on each side was in vlan 2 and vlan 3.
    > > > both vlans in there own subnet
    > > > we configured a trunking port to connect each of them
    > > > all worked fine for the host in the vlans talking to the host in the

    > same
    > > > vlan on the other switch
    > > > then we tried to put a router in between the switches
    > > > it was a 2600 with 2 ethernet interfaces
    > > > we tried to set it up but we could not figure out how to do in ip

    > addressing
    > > > on the router
    > > > we came to the conslusion that it cant be done like this because
    > > > you cant assign the same network subnet to more than one interface.
    > > > is there some other way we could have done this??
    > > >
    > > > -dk

    >
    >
     
    FireSword, Nov 28, 2003
    #7
  8. David K

    brian Guest

    dave: were the hosts in one vlan able to communicate with another host
    in a different vlan ?


    "David K" <> wrote in message news:<>...
    > in class today we connected 2 cisco switches toghter with 2 host on each
    > switch
    > each host on each side was in vlan 2 and vlan 3.
    > both vlans in there own subnet
    > we configured a trunking port to connect each of them
    > all worked fine for the host in the vlans talking to the host in the same
    > vlan on the other switch
    > then we tried to put a router in between the switches
    > it was a 2600 with 2 ethernet interfaces
    > we tried to set it up but we could not figure out how to do in ip addressing
    > on the router
    > we came to the conslusion that it cant be done like this because
    > you cant assign the same network subnet to more than one interface.
    > is there some other way we could have done this??
    >
    > -dk
     
    brian, Nov 28, 2003
    #8
  9. David K

    brian Guest

    your example is fine but what the original poster scenario is that the
    same vlan is present in different switches.
    ie host1 and and host2 are connected to separate physical switch.

    so now the router has to carry the trunk as well (in addition to
    routing between the two vlans).



    "FireSword" <> wrote in message news:<>...
    > When you use 2 router interfaces to route between vlans you do not use a
    > trunk to the router.
    > You should have 3 switch ports on vlan 2 (mode access), and 3 switch ports
    > on vlan 3 (mode acess).
    > In vlan 2 you will have 2 hosts AND one of the router interfaces.
    > The same for VLAN3.
    > Example:
    >
    > VLAN 2
    > Three Acess Ports
    > Port 1 - router eth0 10.1.1.1/24
    > Port 2 - host 1 10.1.1.2/24
    > Port 3 - host 2 10.1.1.3/24
    >
    > VLAN 2
    > Three Acess Ports
    > Port 1 - router eth1 10.2.2.1/24
    > Port 2 - host 1 10.2.2.2/24
    > Port 3 - host 2 10.2.2.3/24
    >
     
    brian, Nov 28, 2003
    #9
  10. David K

    FireSword Guest

    Brian,

    A trunk is only needed BETWEEN the switches, no to the router because he
    does not want to use ISL or 802.1q.

    He wants to use 2 ethernet interfaces that will not understand any trunk
    encapsulation.

    That is why in my example I dond say SWITCH 1, I say VLAN 1.
    J. Rivera

    "brian" <> wrote in message
    news:...
    > your example is fine but what the original poster scenario is that the
    > same vlan is present in different switches.
    > ie host1 and and host2 are connected to separate physical switch.
    >
    > so now the router has to carry the trunk as well (in addition to
    > routing between the two vlans).
    >
    >
    >
    > "FireSword" <> wrote in message

    news:<>...
    > > When you use 2 router interfaces to route between vlans you do not use a
    > > trunk to the router.
    > > You should have 3 switch ports on vlan 2 (mode access), and 3 switch

    ports
    > > on vlan 3 (mode acess).
    > > In vlan 2 you will have 2 hosts AND one of the router interfaces.
    > > The same for VLAN3.
    > > Example:
    > >
    > > VLAN 2
    > > Three Acess Ports
    > > Port 1 - router eth0 10.1.1.1/24
    > > Port 2 - host 1 10.1.1.2/24
    > > Port 3 - host 2 10.1.1.3/24
    > >
    > > VLAN 2
    > > Three Acess Ports
    > > Port 1 - router eth1 10.2.2.1/24
    > > Port 2 - host 1 10.2.2.2/24
    > > Port 3 - host 2 10.2.2.3/24
    > >
     
    FireSword, Nov 28, 2003
    #10
  11. when we just had the 2 switches connected toghter with the trunk the vlans
    were unable to talk to each other, this is what we wanted.

    we then left the switches connected, and add added the router to one of the
    switches
    this let the vlans talk to each other.

    but when we tried to put the router inbetween the switches nothin worked i
    think.

    I will be back in class tuesday to try out some of the things that you guys
    have posted.

    Thanks To all that have helped out so far

    -dk

    "brian" <> wrote in message
    news:...
    > dave: were the hosts in one vlan able to communicate with another host
    > in a different vlan ?
    >
    >
    > "David K" <> wrote in message

    news:<>...
    > > in class today we connected 2 cisco switches toghter with 2 host on each
    > > switch
    > > each host on each side was in vlan 2 and vlan 3.
    > > both vlans in there own subnet
    > > we configured a trunking port to connect each of them
    > > all worked fine for the host in the vlans talking to the host in the

    same
    > > vlan on the other switch
    > > then we tried to put a router in between the switches
    > > it was a 2600 with 2 ethernet interfaces
    > > we tried to set it up but we could not figure out how to do in ip

    addressing
    > > on the router
    > > we came to the conslusion that it cant be done like this because
    > > you cant assign the same network subnet to more than one interface.
    > > is there some other way we could have done this??
    > >
    > > -dk
     
    David Kierzkowski, Nov 28, 2003
    #11
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