Cisco 4503E`

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Overall Rating: 5 (1 ratings)
Jon Marshall Mon, 09/20/2010 - 02:35


Edit - I have just reread post and realise you have a Sup3 in your chassis (my fault for not reading properly in the first place). I'll leave the rest of the post as is though as it still seems fairly relevant, and i'm not the fastest typist so it did take a bit of time to type it all

The answer is, it depends.

If you have the Supervisor 6-E in your chassis and the SFP module is an E series module then no it won't because each with the Sup 6-E each slot has 24Gbps connection to switch fabric so there is no oversubscription.

If you don't have a Sup 6-E and/or the module is not an E series module then if the SFP module has more than 6 connections there is possibility for oversubscripton because each module only has a 6Gbps connection to the switch fabric. Note it's not quite as straightforward as to whether it just has 6 or not because usually modules are broken down into port groups and each port group is tied to an ASIC so you my have 6 or more connections but be tieing them all the same ASIC in which case simply moving your WAN connection to another ASIC within the module may help.

It depends on the actual module so if you have doubts then just post module number here.

However it is safe to say that if the module is fully populated or near fully populated then yes there is the potential for the WAN port to be contending with other ports for access to the switch fabric.

Do you really need 1Gbps for the WAN ie. what is the actual speed of the circuit for your WAN.

In the above case it may well make sense to move the WAN connection to the supervisor card.

Another benefit of havng the WAN port connected into the supervisor is if you are running a dynamic routing protocol between this 4500 and something on the WAN. Because the supervisor boots up first when the switch is reloaded it can establish the peering before any devices are ready to start forwarding. Having the WAN connection on the SFP module means, depending on the order the modules are booted, there may be devices ready to forward data across the WAN but can't because there are no routes for the WAN yet as the SFP module hasn't booted up.

So there is no right or wrong answer to this, it just depends on your modules and supervisor.



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