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Multiple VLANS on the same port with same subnet

I asked a question last week about using private vlans, and the answers I got seem to indicate this may not be the right way to do this.

Anyway, here's what I'm trying to do.

I have a port:

interface GigabitEthernet1/0/25

description DSLAM #2

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 157,224,301,302,401,402

switchport mode trunk

switchport nonegotiate

end

I'd like to set this up so that vlans 157, 301, and 302 share the same subnet, and 224, 401, and 402 share an entirely different subnet.

Due to the nature of the DSLAM attached to the port, I have to have these on seperate VLANS.

Is private vlans the way to go? Is there any other way to do this?

thanks,

Ben

5 REPLIES
Hall of Fame Super Silver

Re: Multiple VLANS on the same port with same subnet

Hello Ben,

you can use IRB = integrated routing and bridging that on switch is also called inter-vlan bridging

bridge 1 protocol x

bridge 1 route ip

int bvi 1

ip address x.x.x.x 255.255.255.0

desc L3 interface for first vlan group

!

int vlan 157

no ip address

bridge-group 1

int vlan 301

no ip address

bridge-group 1

int vlan 302

bridge-group 1

the same can be done for the second group.

I did this inter-vlan bridging on a c3550, and it worked for non ipv4 traffic.

On a C6500 can work also for ipv4 traffic.

your device looks like to be a 3750 and is called fallback bridging:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750e_3560e/software/release/12.2_46_se/configuration/guide/swfallbk.html

here may be you can add a routed port for each bridge-group instead of a BVI.

Hope to help

Giuseppe

New Member

Re: Multiple VLANS on the same port with same subnet

I've actually got a 3750G running Version 12.2(25)SEB4.

the first of these commands you gave me

bridge 1 protocol x

bridge 1 route ip

appear not to work. Is there anything I need to do prior to this, or is it something that I need either an IOS upgrade or a new product in order to do?

thanks,

-Ben

Hall of Fame Super Silver

Re: Multiple VLANS on the same port with same subnet

Hello Ben,

>> bridge 1 protocol x

this was a type error try ieee instead of x and follow the link for the details

Hope to help

Giuseppe

New Member

Re: Multiple VLANS on the same port with same subnet

hrm. it looks like "bridge" isn't even a viable option. is there something I need to enable first?

-Ben

Hall of Fame Super Silver

Re: Multiple VLANS on the same port with same subnet

Hello Ben,

if this is not available

bridge bridge-group# protocol vlan-bridge

I think it is not supported in your current IOS release

Hope to help

Giuseppe

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