3750 InterVlan Routing

soshomile · ‎01-05-2009

Hi All;

i have some questions regaring 3750 IVR configuration.

1. for IVR i didnt make any port of 3750 layer3 port. but 3750 is routing between my Vlans. is this Layer 3 routing ?

2. is it necessary to make layer 3 port by making "no switchport" command?

3. How can we change encapsulation of subinterface of Layer 3 port.

please help me in this regard.

regards

soshomile

mahmoodmkl · ‎01-05-2009

Hi

The 3750 is a L3 switch.

U need not create any L3 ports on the 3750 as u create SVI's for the specific vlans,they are going to take care of IVR.

no it is not necessary to make L3 ports using no switchport this depends upon u r requirement.

AFAIk u cannot create sub-interfaces on this switch.

Thanks

Mahmood

soshomile · ‎01-05-2009

Dear thankyou.

for more detail please consider this example;

enduser first switch is 2950....it has 5 Vlans...Vlan 10-20-30-40 and 50. then i have another layer 2 switch 3500. i just make these Vlan into this as well. then i have 3750 fiber switch,. there i make all Vlan and assign the IP address which would be default gateway for the clients those are behind 2950 switch. for DHCP relay ...now i need to configure IP Helper-address on Vlan20...like

Vlan 20

ip address 1.1.1.1 255.0.0.0

ip helper-addres 10.1.1.1 255.0.0.0

by doing this my HDCP relay would configure...i already check that my client is able to ping the DHCP server.

is this complete configuration..?

please advice

regards

Soshomile

Giuseppe Larosa · ‎01-05-2009

Hello Soshomile,

a multilayer switch can use logical interfaces called SVI for inter vlan routing :

vlan 2

name l2object

interface vlan 2

desc L3 SVI associated to vlan2

ip address x.x.x.x 255.255.y.z

think of it as a device connected to vlan2

you probably have SVIs on your C3750 if you are able to perform inter-vlans routing or an external device is doing it.

2) no see above

3) no you cannot do like in a router: you create SVIs for all vlans

the physical port is configured as a layer 2 trunk carrying vlans of interest

int g0/1

desc trunk to other device

switchport trunk encapsulation dot1q|isl

switchport mode trunk

swithcpot trunk allowed vlan 1,2,

the result is that all Vlans SVIs can talk with the outer world

Hope to help

Giuseppe

lejoe.thomas · ‎01-05-2009

Hi soshomile,

1. for IVR i didnt make any port of 3750 layer3 port. but 3750 is routing between my Vlans. is this Layer 3 routing ?

As long as VLAN interfaces are up, configured with an IP address and you have enabled ip routing globally on the 3750, intervlan routing works

2. is it necessary to make layer 3 port by making "no switchport" command?

For the purpose Intervlan routing, you need not define a Layer 3 port. However if you wish to have L3 port on the switch, use the no switchport command under interface configuration mode.

3. How can we change encapsulation of subinterface of Layer 3 port.

The concept of using a subinterface for intervlan routing is when a router of stick method is used. However, here all you need is trunk port on the switch to pass all the VLANs.

Refer below for more details

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a00801cc828.shtml

HTH

Lejoe