cat 6500 vlans and 4500m router

[ldodd]

hi we are using 4500m routers as our wan routers, we are about to put in catalyst 6500s and segment our lan into vlans I have 6 10meg interfaces in the 4500's is there an advantage to using the 10 meg interfaces of the wan router (running eigrp) with one connected to each vlan ? is there a disadvantage to doing or not doing it?

[stpowney]

This depends on how many 4500's you have and how you will connect them for management traffic. eg. If you have 6 4500's one for each vlan you will need an additional way of connecting them all together so that they can communicate eigrp traffic etc. Remember as you have only mentioned 10Meg (I presume Ethernet) links trunking will NOT be an option.

[ldodd]

actualyy its 1 4500 and 1 6500 at each site

i was wondering if ther was a good design reason to or not to connect the 6 10 meg eth intfcs 1 to each vlan i will use on 6500

[mbjohnson]

My question is why would you want to use 6 10mb ports? Using one 100mb port and creating a trunk between the router and the 6500 will be much easier.

Good luck.

[ldodd]

i have no 100 meg ports on the wan router

i just want to know if it is good or bad or doesnt matter if the wan router is directly connected to the vlans in the 6500

i know the 6500 can handle all the routing or hand off to the 4500 for wan BUT is there any advantage to using up the 6 10 meg eth ports that i dont really need for anything else.

so is there any reason not to do this if not then is there any benefit to doing it ?

[johansens]

Let's do some thinking:

If you use the 6500 MSFC to do the inter-VLAN routing, what could you gain from placing the WAN router in each segment?

All sessions to a segment which traverses the WAN router would get an ICMP Redirect from the MSFC, and it's up to the client/server to respect this.

Now, let's say the client/server respects the Redirect and uses the WAN router's 'local' interface in the VLAN for subsequent packets. What have you gained; one less hop (but this hop was done at lightning-speed anyway, so no real gain). Now, which other benefits do you have;

- You have one dedicated interface per VLAN

This means potentially more bandwidth into the router, and less collisions/retransmits. Now it's up to the WAN side of the router to shuffle this traffic on. One of the downsides to this configuration is that the WAN router must process a lot more broadcasts than in a single uplink scenario. Another downside is the added complexity of the network; makes any debugging more difficult.

As you see, there are payoffs but not without some cautions.

Just my 2 cents..

//Stig