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cisco vlan routing question

 
 
David K
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      11-26-2003
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


 
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Salus
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      11-26-2003
..Q and ISL trunking available on the router IOS?

Salus
 
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FireSword
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      11-26-2003
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" <(E-Mail Removed)> wrote in message
news(E-Mail Removed)...
> 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
>
>




 
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David K
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Posts: n/a
 
      11-26-2003
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" <(E-Mail Removed)> 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" <(E-Mail Removed)> wrote in message
> news(E-Mail Removed)...
> > 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
> >
> >

>
>
>



 
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Jeff Specoli
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      11-26-2003
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" <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>...
> 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

 
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David K
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Posts: n/a
 
      11-27-2003
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" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> 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" <(E-Mail Removed)> wrote in message

news:<(E-Mail Removed)>...
> > 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



 
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FireSword
Guest
Posts: n/a
 
      11-28-2003
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" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> 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" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) om...
> > 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" <(E-Mail Removed)> wrote in message

> news:<(E-Mail Removed)>...
> > > 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

>
>




 
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brian
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Posts: n/a
 
      11-28-2003
dave: were the hosts in one vlan able to communicate with another host
in a different vlan ?


"David K" <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>...
> 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

 
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brian
Guest
Posts: n/a
 
      11-28-2003
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" <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>.. .
> 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
>

 
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FireSword
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Posts: n/a
 
      11-28-2003
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" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> 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" <(E-Mail Removed)> wrote in message

news:<(E-Mail Removed)>.. .
> > 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
> >




 
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