mohammedrafiq wrote:
Hi,
We have three tier Cisco network Core 6513(Dis and Access connected)- Distribute 6509(Servers connected)-Access/Agg 6506 (user connected through 4500 switches).We have Layer 3 network between all, expect between 6506 and 4500 where all is layer2. We like to implement multimedia apps like VOIP, IPTV etc.Now we have to make decision that what will be the best practice, to keep L2 between 6506 and 4500 or change it also to L3 as route at network edge?
Any suggestion welcome.
Regards.
Mohammed
It all depends. A routed access-layer has better failover times than a L2 access-layer and with apps such as VOIP this can be important. We have used the routed access-layer at the last place i worked and it did the job well but it does impose certain restrictions the main one being that you can no longer have the same vlan on multiple access-layer switches. Whether or not this is an issue only you can say but if you can isolate the vlans to each access-layer switch then L3 in the access-layer is a viable alternative.
What we had was each floor was allocated a data vlan and a voice vlan and these were routed locally on that floor. We then had point-to-point L3 routed links back to the distro/core switches. We used EIGRP stub on each floor which significantly reduced the size of the routing tables at the access-layer.
Note that with RSTP failover times with L2 are now significantly reduced from standard STP so L2 is still a time and tested design which would work with VOIP and IPTV.
If you haven't already seen it have a look at this L3 routed campus design -
L3 routed campus
Jon
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