VLAN routing between multiple switches?

rwillman483 · ‎08-24-2006

We've got two 4506 cores with 3550's on each floor (9 floors) and a couple Nortel layer 2's connected to the 3550's. We want to have each floor be a separate VLAN. Everything I have read talks about doing VLAN routing on ONE switch? That is ok but my initial thought was that it would be better performance wise to offload routing to each 3550 with the cores just passing traffic between them. Is this possible or do I need to do all the routing on the 4506s? How would I do it?

My other question is I read a Cisco article that talks about doing HSRP between two switches (my 4506s) for failover. Assuming I have to do the routing on the 4506s how do I set up the config as far as VLAN routing goes? Do I need to set up VLAN interfaces on both cores? Does the config on each one need to be identical?

Any advice is greatly appreciated.

Edison Ortiz · ‎08-24-2006

4506 switches should perform the inter-vlan routing.

Since all switches will interconnect via the 4506, it makes sense to have a central device for routing and vlan management.

First off, you will assign both 4506s as VTP servers and the 3550s running as VTP client.

You create all the VLANs for each floor on these switches and their respective SVIs (Switch Virtual Interface).

The layer2 information will be automatically propagate to all VTP clients under the same domain.

Once the layer2 informaton is verified on each 3550, you can assign port membership per floor.

The SVIs on the 4506 will contain IP Address for each subnet, this will function as the subnet default gateway.

The SVIs would look like this:

interface Vlan1

description 1st Floor LAN

ip address 192.168.1.1 255.255.255.0

ip helper-address [DHCP SERVER IP]

no ip redirects

interface Vlan2

description 2nd floor LAN

ip address 192.168.2.0 255.255.255.0

ip helper-address [DHCP SERVER IP]

no ip redirects

do the same for all floors.

HSRP is also recommended here and you would configure under each SVI.

For instance, VLAN1 HSRP

4506 Router 1

interface Vlan1

description 1st floor LAN

ip address 192.168.1.2 255.255.255.0

standby ip 192.168.1.1

standby ip priority 150

standby preempt

ip helper-address [DHCP SERVER IP]

no ip redirects

4506 Router 2

interface Vlan1

description 1st floor LAN

ip address 192.168.1.3 255.255.255.0

standby ip 192.168.1.1

standby preempt

ip helper-address [DHCP SERVER IP]

no ip redirects

Please rate helpful posts.

Thanks

sundar.palaniappan · ‎08-24-2006

Hi,

The legacy approach is to configure routing on the core switches and access switches would only serve as layer 2 switches. Your consideration to enable routing on the access switches for their respective VLANs is a better choice and should offload the burden put on the core switches a great deal.

HSRP on the core switches should provide you redundnacy for the 3550's. Configure all the uplinks from the 3550 to the core switches to be on the same access VLAN, create a SVI for that VLAN on the core switches, create two HSRP groups on that VLAN. Make each core switch to be the active router for one HSRP group. All your 3550's can used two default routes to point to those two HSRP addresses. This setup should provide load balancing across both switches and redundancy, if one switch should fail.

Hope that helps!

Regards,

Sundar

rwillman483 · ‎08-24-2006

Thanks that helps quite a bit. I have one other related question. Each 3550 is uplinked to the cores via 2 fiber cables, one link to each core.

I would like to enable etherchannel on these fiber links but from what I have read we would have to move both links to the same core as etherchannel doesn't work between multiple switches. Is that correct? Will implementing this change the configuration you gave me? What would that be? Thanks again this really helps me out.

Edison Ortiz · ‎08-24-2006

You can't configure etherchanneling when connecting to different hardware destination on each link.

I would concur with Steve Riggs's suggestion but personally, I have not implemented myself.

What kind of sample configuration do you need ? Etherchanneling ?

Please rate helpful posts.

Thanks

sundar.palaniappan · ‎08-24-2006

Hi,

1. 'I would like to enable etherchannel on these fiber links but from what I have read we would have to move both links to the same core as etherchannel doesn't work between multiple switches. Is that correct?'

Yes

2. 'Will implementing this change the configuration you gave me?'

No. With etherchannel you are bundling multiple ports into channel group and the layer 3 configuration would still be applied on your SVI interface. I don't think you can do multi-chassis etherchannel.

Here's a couple of links that you may find useful in configuring etherchannel.

http://www.cisco.com/en/US/products/hw/switches/ps4324/products_configuration_guide_chapter09186a008062ce84.html

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a00800949c2.shtml

Hope that helps!

Regards,

Sundar

abhishek_nandavat · ‎08-24-2006

Hi,

I would agree with what EdisonOrtiz has suggested. Routing should be done centrally by the core switches.

HSRP is definitely recommended!

Refer the following link for details on configuring HSRP:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hiap_c/ch20/haiphsrp.htm

Hope this helps!

Regards,

AbhisheK

Please rate all posts!!!

sriggslev · ‎08-24-2006

How about L3 P2P links from access to core and a routing protocol to provide load balancing and redunancy ?? A properly configured routing protocol will provide better convergence times than STP and will alow for true load sharing....