From: James (james@towardex.com)
Date: Wed Sep 08 2004 - 00:48:43 GMT-3
On Wed, Sep 08, 2004 at 11:01:50AM +1000, Devi Mallampalli wrote:
> Thanks , James / Dustin / Chad & Adebola.
Sure no problem.
>
> Your feed back is very helpful. Just to clarify further , yes I was
> planning to run BGP on 3550s for dynamic fail over purposes ONLY at our
> Internet boundary and will NOT be trying to exchange full BGP routing
> table with our ISP peer devices. I will be negotiating similar policy
> with my ISP as well so that they will only leak cut down size of
> internet table. In other words , I was looking for a fail over
> capability rather than Full Route specifics. Secondly TCAM related
> scalability issue which James pointed out is really important one , I
> guess. As I am certain that I will be doing some kind of advanced PBR ,
> Qos & Security features down the track , I am now having second
> thoughts about deploying 3550s as edge router at our Internet perimeter.
That's a good idea. Like I mentioned above, when we used it for edge,
it just held internal routes and a default even though we spoke BGP to the
core, which should work well for you.
>
> Having said that, I will still try to deploy 3550 as an edge router at
> one of our spoke sites who does not need any fancy Qos or ACLs or 20 odd
> multiple Vlans.I think they will do just fine on that kind of small 20
> odd user spoke site because we can , not only eliminate Access switch
> costs (typically we use 2950s closer to the users) by connecting all
> user's desktops directly to 3550s, but also Router costs by connecting
> BDSL WAN Ethernet interface directly to one of 3550s switch ports. And
> they can happily do IGP/EIGRP routing for up to 500 odd routing table
> (well I am not doing stubb routing yet at my tail sites) , I reckon:-)
I think it will be a good idea to give it a try. It is true that limits of
SVI and TCAM is an issue, but really depends on your needs and how much work
your 3550 will end up doing. Some commands you can use to figure out tcam
usage:
! Shows acl label availability. Try not to let it run out of it
sh tcam ina 1 stat
sh tcam outa 1 stat
! PBR label availability
sh tcam pbr 1 stat
! QoS labels
sh tcam qos 1 stat
It is good idea to pay close attention to how much usage you are putting on
the TCAM and try not to exceed it. As long as TCAM is not exceeded, 3550 can
move packets in an impressive manner, for layer3.
Note that using switch database manager, you can format the TCAM's per the
requirements of what your switch is doing, although default configuration
works OK for most environments.
The following URL is a must-read for anyone looking to start doing some
real work on 3550 in L3, to understand potentials for resource contention
and pre-planning in accordance to your network's needs and environment:
http://www.cisco.com/en/US/products/hw/switches/ps646/products_tech_note09186a0080094bc6.shtml
HTH,
-J
-- James Jun TowardEX Technologies, Inc. Technical Lead Network Design, Consulting, IT Outsourcing james@towardex.com Boston-based Colocation & Bandwidth Services cell: 1(978)-394-2867 web: http://www.towardex.com , noc: www.twdx.net
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