02-21-2008 10:08 AM - edited 03-03-2019 08:49 PM
Can anyone help me out with setting up a router interface with more than one subnet. We have 4 buildings all on different subnets. We want all of the subnets to be able to talk and see each other. Each building has fiber to it and we are upgrading from 4 routers to 1, we bought a 2821 router and can't figure it out.
02-21-2008 10:38 AM
What type of switch each building has? You should be able to accomplish inter-vlan routing with Layer3 switches. It's more efficient than having a router perform that function.
If you have a 3560, 3750, 4500 or 6500 switch in your network - you have the ability to configure those devices as routers.
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Edison.
02-21-2008 10:40 AM
We have HP Procurve switches.
02-21-2008 10:41 AM
If you are planning to use sub-interfaces, here is sample config;
interface FastEthernet0/0.1
description building-1
encapsulation dot1Q 1 native
ip address 1.1.1.1 255.255.255.0
no snmp trap link-status
!
interface FastEthernet0/0.2
description building-2
encapsulation dot1Q 2
ip address 2.2.2.2 255.255.255.0
no snmp trap link-status
!
interface FastEthernet0/0.3
description building-3
encapsulation dot1Q 3
ip address 3.3.3.3 255.255.255.0
no snmp trap link-status
HTH
Reza
02-21-2008 10:43 AM
will i still need to create a vlan?
02-21-2008 10:53 AM
yes, you do.
Example:
Switch in building-1 VLAN 1
Switch in building-2 VLAN 2
Switch in building-3 VLAN 3
etc
02-21-2008 10:56 AM
and my router will know which vlan to go over by the ip correct?
02-21-2008 10:50 AM
do i need to setup an ip just for the interface of just for the sub interface?
02-21-2008 11:05 AM
you need 1 subnet per sub-interface
02-21-2008 11:24 AM
Do i need to make all of the native?
02-21-2008 11:42 AM
You are only allow to have one native Vlan in dot1q trunking. The native vlan is defined as the 'untagged vlan'. You need to match the untagged vlan from your procurve switch with the one configured at the router. The router will know what vlan the packet is coming from based on the tag on the packet header.
Keep in mind, on this design - you will have a bottleneck at the router LAN interface and your inter-vlan throughput will be limited to the speed of the LAN interface on this router.
I really recommend getting some Layer3 switches, they don't need to be Cisco brand. HP also sells Layer3 switching equipment.
HTH,
__
Edison.
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