L3 switch

[Tareq Emad Al Asfoor]

dear all ..

i have three network ... i want to conect the three network to L3 switch cisco .. and communicate the three network together ... what it is the right  configuration i must do to do that ???

network 1     :-  10.10.10.0/28

network 2    :-   10.20.20.0/28

network 3    :-    10.30.30.0/28

regards ...

[Jon Marshall]

tariqemad wrote:
dear all ..
i have three network ... i want to conect the three network to L3 switch cisco .. and communicate the three network together ... what it is the right  configuration i must do to do that ???
network 1     :-  10.10.10.0/28
network 2    :-   10.20.20.0/28
network 3    :-    10.30.30.0/28 
regards ...

1) create vlans in vlan database ie.

vlan 10 name v10

vlan 11 name v11

vlan 12 name v12

2) create L3 interfaces for vlans -

int vlan 10

ip address 10.10.10.1 255.255.255.240

int vlan 11

ip address 10.20.20.1 255.255.255.240

int vlan 12

ip address 10.30.30.1 255.255.255.240

3) allocate switchports in to the correct vlans eg.

int gi0/1

switchport mode access

switchport access vlan 10

so a PC connected to int g0/1 would have an address from the 10.10.10.x range and it's default-gateway would be 10.10.10.1

4) depending on the switch you may need to enable ip routing ie.

switch(conf t)# ip routing

Jon

[Tareq Emad Al Asfoor]

ok thank you very much jon ...

you mean when i use 

switch(conf t)# ip routing    

the routing add dynamic ???? ... and if i have network 4  conect after network 3 i must add the ip route for the network 4 static in the switch ??

regards

[Jon Marshall]

tariqemad wrote:
ok thank you very much jon ...
you mean when i use  
 switch(conf t)# ip routing     
 the routing add dynamic ???? ... and if i have network 4  conect after network 3 i must add the ip route for the network 4 static in the switch ??
regards 

You don't need to add any routes because the switch will see the networks as directly connected. Just give it a go and you'll see what i mean.

Jon

[Tareq Emad Al Asfoor]

ok .. thank you so much for u'r help

[cadet alain]

Hi,

You have 2 options: leave ports as L2 ports and use SVIs to to routing between the subnets(VLANs) or put the ports as L3 ports

Let's suppose option 1:

network 1     :-  10.10.10.0/28  VLAN 10

network 2    :-   10.20.20.0/28  VLAN 20

network 3    :-    10.30.30.0/28  VLAN 30

ip routing

int f0/0

switchport mode access

switchport access vlan 10

int f0/1

switchport mode access

switchport access vlan 20

int f0/2

switchport mode access

switchport access vlan 30

int vlan 10

ip address 10.10.10.14 255.255.255.240

int vlan 20

ip address 10.20.20.14 255.255.255.240

int vlan 30

ip address 10.30.30.14 255.255.255.240

second option:

ip routing

int f0/0

no switchport

ip address 10.10.10.14 255.255.255.240

int f0/1

no switchport

ip address 10.20.20.14 255.255.255.240

int f0/2

no switchport

ip address 10.30.30.14 255.255.255.240

on each host as a default gateway put ip address of the int Vlan corresponding to the subnet

Regards.

Alain.

[Jon Marshall]

Alain

I can't see how your second option would work. How do you then connect a client to the switch, and what vlan would it be in ?

Jon

[Tareq Emad Al Asfoor]

yeah i think also that !!! how can do that ?? please Alain if you can explain more about the second choice 

[cadet alain]

Hi Jon,

the switch is acting like a router as there are only L3 ports so there 3 conected subnets and no need for routing protocol or static routes on the switch.

Am I completely wrong? I'm gonna try it on a 3550 this evening.

Regards.

Alain.

[Jon Marshall · Accepted solution]

cadetalain wrote:
Hi Jon,
the switch is acting like a router as there are only L3 ports so there 3 conected subnets and no need for routing protocol or static routes on the switch.
Am I completely wrong? I'm gonna try it on a 3550 this evening.
Regards.
Alain.

Alain

If you had 3 other switches and you connected them to your routed ports, one for each vlan then i can see how it would work. But if you need to connect the clients to the same switch how do you then tell them which vlan they are in ? It's not to do with routes, it's to do with how clients on the same switch could use the routed ports as their gateways because there is now no L2 connectivity from the client to it's default-gateway.

Let me know how you get on though, as i have been wrong many times before

Jon

[Tareq Emad Al Asfoor]

dear ..

my plan is to connect three router ( three network )  to the L3 switch .. then from each router connect to another router ... so now i can do that by the Alain configuration ???

tariq

regards 

[Jon Marshall]

tariqemad wrote:
dear .. 
my plan is to connect three router ( three network )  to the L3 switch .. then from each router connect to another router ... so now i can do that by the Alain configuration ???
tariq
regards  

I think Alain and I read the question a bit differently.

My answer was based on the idea that the clients would also be connecting to the same switch. However if you simply want to use the L3 switch to route between networks but no clients will be connected to the switch then Alain's second option would indeed work.

Jon

[Tareq Emad Al Asfoor]

ok thank you

[cadet alain]

Hi Jon,

I just tried with 2 laptops directly connected on 2 routed ports in 2 different subnets on a 3550 and it works.

Regards.

Alain.

[Jon Marshall]

cadetalain wrote:
Hi Jon,
I just tried with 2 laptops directly connected on 2 routed ports in 2 different subnets on a 3550 and it works.
Regards.
Alain.

Alain

I think we both read the question differently. The test you did will indeed work. What i was saying if you took one of those laptops (or both) and connected them into other (non-routed) ports on the 3550 how do you then assign them the routed ports IP addresses as default-gateways ?

This is where i think we answered different questions ie. you were talking about making the switch a router and any clients were either connected directly to the routed ports or were connected to other switches which then connected to the routed ports. I agree that this would work.

What i was talking about was having all the clients connected to the same switch as the routed ports are on. If you did this you couldn't assign a client into a vlan and then use a routed port on the same switch as it's default-gateway.

Am i making sense ?

Jon