Network Design L2 network to L3

[UselessUser]

Hi,

We have a sprawling L2 network which consists of a large number of 24 and 48 port switches...

We also have a few 4200 devices and a few 5300 devices... spread across a few buildings

The LAN is currently completely flat... which I am looking to break up... (For obvious reasons I am sure anyone reading this will be aware of!)

I was wondering what people would recommend on this... seeing as we have multiple L3 capable devices in each building we were thinking of creating an OSPF triangle (Using the single 5300 in each building), and then placing everything else that is L2 behind these devices...

The L2 devices would have VLAN's terminated by the 5300's...

The concern I have is that we would be using the 5300's as access(They have a lot of client ports on them)/distribution/core devices all in one... Is this HP's idea?

Obviously doing the above would allow us to eventually phase out all L2 thus shrinking STP and VLAN's down to encapsulate only their own switches and giving us a fully L3 network.

We could at some point swap out the 5300's for 5400's and 3500's in areas of small density and then utilize some of HP's Identity Management etc which would come in handy for us...

Any suggestions would really be appreciated, and if anyone reading this has more questions I will respond!

[Mohammed Faiz]

Hi,

You shouldn't have any issues with using your 5300's as access switches as well as distribution/core devices. If you do choose that option you may want to do some tweaking with STP around admin-edge ports depending on what types of client you have connected to the 5300's.
If you can re-arrange your networks/VLANs at the same time to avoid having VLANs traversing the core you will save yourself a lot of effort in having to configure both L2 and L3 resiliency in your core.
Updating to 5400's would be a good idea as software development on the 5300 series seems to have come to and end some time ago.

[UselessUser]

Hi,

Thanks for the response...

We are going to have PC's and VOIP phones connected to most ports... I assume you mean basically turn off STP for anything which we know will not be a loop and leave it on for anything else?

The part you mention about the core is interesting in that I do not anticipate actually having a core device... I assume you mean keeping the VLAN's contained within each 5300's own area... thus avoiding spanning a VLAN... if this is what you mean, this is what I intend to do... breaking up VLAN's by building... therefore a single VLAN will never span past the 5300 in each building...

Also a final question... in terms of linking each 5300/5400 back to each other to create the core network... if I use 2 fibre ports...

Is it best to create a trunk group consisting of both ports and use this single logical link, or keep each link as a seperate entity?? If it helps we are looking at using OSPF for the core triangle (Thus it will be L3 and therefore both links could be active) and statics on anything else behind each 5300...

[Mohammed Faiz]

Hi,

> .. I assume you mean basically turn off STP
> for anything which we know will not be a
> loop and leave it on for anything else?

More along the lines of, if you have devices that you want to ensure come online asap after a link down/link up event (e.g. a server) you can configure them as admin-edge port so that they move straight to the forwarding state.
I'd leave things like bpdu-protection enabled just to be on the safe side.

> assume you mean keeping the VLAN's
> contained within each 5300's own area...
> thus avoiding spanning a VLAN.

Yup, that's exactly what I meant and I envy the fact that you can do that with your network :)

> Is it best to create a trunk group
> consisting of both ports and use this
> single logical link, or keep each link
> as a seperate entity?

My choice would be to trunk the links together. It would mean a simpler config, compared to having four OSPF links per switch and would simplify troubleshooting any issues.
There may be an argument to say that one form of loadbalancing is better/more efficient than the other (i.e. trunks vs OSPF ECMP) but I'm not sure what the answer would be to that.

[UselessUser]

Hi,

Thanks for the response... glad we are on the same pages!!

Out of curiosity... love to learn etc...

Why is it that you cannot keep VLAN's compartmentalized??

[Mohammed Faiz]

We have a few systems that just aren't designed to communicate across networks. The Building Management System that our estates team use being one example.
The are other cases like the VMWare infrastructure where in order to allow VMs to be VMotion'ed between datacentres the VMotion network needs to span the core.