From: Chad Hintz (ccie_2b2004@yahoo.com)
Date: Tue Sep 07 2004 - 12:06:35 GMT-3
This might be obvious but remember that the 3550's do not do NAT!
James <james@towardex.com> wrote:That's okay, but remember C3550's have really small TCAM sizes, which makes
them not eligible to function as a proper edge router. Watch out for TCAM labels
and masks availability when you add ACL's, watch out whenever you have more than
8-16 routed or SVI interfaces, watchout whenever you have few thousand routes,
watch out when you add QoS policies, etc.
3550's are fine as as long as you keep it simple and don't push it to its
limits. Push to its limits and it will resort to sloooowww software routing.
And the limit of the hardware is clear: its TCAM is so small, unless it is
3550-12T/G which have bigger space, but still small compared with other models.
Also don't expect to do bgp redundancy between two isp's using full routes.
It won't hold full routes.
I used to use c3550's as "edge router" device for colocation customers. It did
not scale for us. We ended up having more than 24 vlan's routed (SVI's) for each
customer on the box, and 3550 just smoked, since we went past its limits. Add
ACL's to the equation and situation becomes worse by that point.
HTH,
-J
On Tue, Sep 07, 2004 at 09:22:56PM +1000, Devi Mallampalli wrote:
> Hi Group,
>
> Got a real world scenario at hand and would like to gather your thoughts
> on this :-)
>
> I am seriously planning to replace our Internet Router/2651 and its
> expensive 2MB Frame circuit with that of Layer 3 switch (either 3550 or
> 3750) and with lesser expensive 2 MB BDSL (Business DSL) WAN circuit
> which is delivered on to "Ethernet" port on layer 3 switch directly.
> The primary reason of doing this design is to not only to derive direct
> cost savings to the tune of around US$20k per annum (Yes, 4MB HSSI
> installation cost and per annum usage cost are too high when compared to
> a 2 MB BDSL Ethernet circuit) to our corporation , but also to try out
> alternative WAN protocols which can delivered on to an Ethernet/RJ45
> interface rather than on x25 or v35 interfaces (with a long term view to
> replace all Routers on our WAN with that of Layer 3 switches with an
> MPLS core and BDSL combination at remote sites so that we can move away
> with our current HUB and SPOKE Frame relay WAN and instead can have one
> flat , one hop away WAN. Any way that is different story)
>
> But before I proceed I just want to have a second opinion on whether or
> not it is a good idea to assign Internet periphery responsibility to a
> Layer 3 switch , rather than a decent Router such as 2651 XM , primarily
> from both Qos and required Redundancy point of view.
>
> Qos , because I am not 100% on whether or not I can do Shaping ,
> Policing , Policy Routing and IP Routing on Ethernet interfaces of
> 3550/3750 to the same "Degree" as that of Routers/2651XM serial
> interfaces ? And more over , I was wondering with this Layer 3 design ,
> I will be loosing congestion indicators such as DEs, BECNs and FECNs on
> the wire and so from what features I can take help on Ethernet WAN
> interfaces(well in my case it is BDSL which is being delivered on to a
> RJ 45 interface at customer premises) to the similar effect ?
>
> Redundancy , since our Internet infrastructure need to support critical
> Ecommerce apps, originally I thought of deploying a back up 2651 as well
> and then run BGP between them and our ISP's Internet edge routers.
> Unlike our current static routing , I was planning to extract more
> effective dynamic fail over between two Routers from L3 protocol/BGP. In
> addition , from L3 protocol I am hoping to do some traffic engineering
> in terms of preferred "outbound" and "inbound" in to our AS. And I am
> not 100% on whether I can do the same things on Layer 3 switches ?
>
> I have seen 3550s operating happily on our N/W in doing roles such as
> "Campus Vlan router" and "switch block aggregator" for 20 odd 7960 IP
> phones ...etc. But I have not seen them in the role of perimeter Routing
> device in doing both Routing functions as well as advanced Qos.
>
> I am inclined towards Layer 3 switching design because 1) we can
> eliminate routers costs 2) it will save us Telco circuit costs as well
> since we are not using expensive WAN protocols such as Frame/HSSI.
>
> But I appreciate any feed back on the intended solution.
>
> Cheers
>
> Devi.
>
>
>
>
>
>
>
>
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-- 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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