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New Member

Vlan in core or routed core?


I would like help with the following:

I have a core switch that will be connected to 4+ distribution switches. The distribution switches will connect to access switches, the Cisco three tier model. The distribution switches are L3 and are dual linked to the core switch, which is L3 as well. The access switches are L2 and will have trunk links to the distribution switches, four vlans configured. I have IP and IPX running and would like to route IP in the core to distribution switch and between Vlans but would like to have a separate vlan for IPX. This will be bridged from the distribution switches to the core so the print servers at the core can print to the printers at the access layer.

Will I need to extend the vlan through the core for the IPX vlan? If so do I need to trunk the links as I need routed ip as well, I am not sure what the best design would be and would appreciate any advise and links to examples if possible.



Re: Vlan in core or routed core?

Route in the core. Extending VLAns or bridging all over the place in your core would increase the likelyhood that you would have a bridging loop that could potentially melt your core down or effect service. Routing gives you a good demarc for your L2 environments. Route IPX in your core if you want or tunnel it if you want to stay IP only in your core.

Hope this helps you,


New Member

Re: Vlan in core or routed core?

Hi Don,

Thanks for the reply, i have a 4507 in the core and 3550 distribution switches, i don't think the 3550 can route IPX? With regards to the tunnels i have never done this so can you help with a url to an example.

Your help would be greatly appreciated.




Re: Vlan in core or routed core?


If only one 4507 in the core you'll not need to tunnel (see GRE or IPinIP tunnels on CCO). I would recommend routing IPX from VLAN to VLAN on the 4507 to keep from the issues I stated in previous post.

Hope this helps you,


New Member

Re: Vlan in core or routed core?

Read the other threads in this forum that talk about performance issues with routing IPX on the 4000 and 4500 switches with the Sup III and IV.

I just visited my second client in two months who has encountered this issue. The first client eliminated IPX from their network altogether. The second client plans to do that in about six months, but is looking for a short-term resolution to the problem. They have already offloaded the IPX routing to an external 3640 router. That didn't help, since after having done that the CPU utilization on the 3640 is averaging 80%.

Aside from that issue, the 4500 is an excellent device.


New Member

Re: Vlan in core or routed core?

If you are Running Novell you can reduce the amount of IPX Traffic if you use NLSP instead of SAP. It's alot less chatty, can support multiable paths and keeps the core clear of all that junk.

In a 6509 routing engine it looks like this


ipx router nlsp MYNLSP

area-address 0 0


interface Vlan615

description L3->6513-01

ip address

no ip redirects

no ip route-cache

no ip mroute-cache

ipx network AC177B78 encapsulation SAP

ipx nlsp MYNLSP enable

That's between Two cat6500's both with L3 in each...

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