L3 switch PLEASE HELP

Chris Knight · August 2008

Guys, confusion is setting in. I have been racking my brain on this one.

If I look at a 7206 or 6000 series layer 3 switch. Is the supervisor card that comes with the switch in essence the "older Netflow" RP and SE? and provided from that, everything is then created into the FIB of the switch?

I guess Im wondering what the sup card is for. For instance like in a 3750 l3 switch, you dont need the supervisor card (for one, it wouldnt fit) as it does routing withing ASICS already and CEF is enabled.

If CEF is enabled by default and can switch packets in ASIC then why even have a MSFC?

I guess I am confused since our work 7206vxr has MLS RP IP enabled under the vlan interface of the MSFC card.

Now "technically" this is using the older RP and switching engine correct? So why in the world would we be using the old MLS routing technique if CEF is enabled? However since CEF is enabled by default, does CEF reside on the MSFC or the switch itself?

Because I can do a sh ip cef on the msfc and it will show the CEF table. I can also do your standard sh ip route and it will show the table as well. Also if I do a sh ip route and sh ip cef under the switch IP they show the same tables as the MSFC card.

PLEASE help me on this! I will respond a bit later. Please help me understand this

Thanks

networker050184 · August 2008

The 7206vxr is an edge router not a switch. I have seen a lot of them on larger enterprise edges but haven't worked with them extensively, so I can't answer all of your questions. You can start here which is what I would do if I were you.

Chris Knight · August 2008

Hmm that is interesting.

IF its an edge router, why in the world when you need a sup card to do routing?

When a packet checks and sees if it can be switching ASIC, is that the MSFC that it is found or the switch itself?

Because again I had though the MSFC is for the older netflow switching and not the topology based CEF switc

dtlokee · August 2008

The reason why the Supervisor architecture is used would be the same as why they use a modular interface design. If you look at the 2500's they were fixed interfaces and you bought a different model based on need. On the 7200 series they give you the option of populating the chassis with a NPE that meets your needs. Then you add in the different interface cards.

networker050184 · August 2008

The 6500's are usually in the core with the 7200 on the edge aggregating large WAN links such as OC-3s. Are you sure you don't have a 7600 with a sup engine?

Forsaken_GA · August 2008

Chris Knight wrote:

Guys, confusion is setting in. I have been racking my brain on this one.

If I look at a 7206 or 6000 series layer 3 switch. Is the supervisor card that comes with the switch in essence the "older Netflow" RP and SE? and provided from that, everything is then created into the FIB of the switch?

Think you may have your model numbers mixed up. The 7200 series is pretty much just a straight router. You generally don't see a 7206 with a boatload of port density. It doesn't use a supervisor engine, it uses an NPE card that loads in the back or an I/O card that loads in the front (unless you're using an NPE-G1 or better, which doesn't require an I/O card)

The module switches like the 4000, 4500, 6000, 6500 et al series and such were switches first (originally) with which you could add router capabilities later through various daughterboards. For most Supervisor's prior to the Sup720, the Supervisor was usually running CatOS, and if you added in an MSFC, it ran IOS and handled your routing capabilities (there are exceptions to this, some older Sup's are capable of running IOS natively).

So to answer your question, in the case of a 7206, no. Totally different concept and aproach. In the case of a 6000 series, yeah, basically.

Chris Knight · August 2008

Thanks for the feedback fellas, however I am still a bit confused.

I will check this out on Mon morning and report back with some configs.

So basically the supervisor cards provide the routing for the module chassis?

Since the 7206vxr is a router anyway, then this MSFC cant be on this router then, as it would defeat the purpose.

I will try and gather more info on Monday.

Thanks all for the help

Forsaken_GA · August 2008

Chris Knight wrote:

So basically the supervisor cards provide the routing for the module chassis?

No, for the most part, the supervisor line cards provide the switching capability, gotta keep in mind that it's only relatively recently that layer3 switching has become predominant. The MSFC daughterboards (for the 6000/6500 series anyway) are what provide the routing capabilities. For old Sup2 and Sup1's, it is perfectly possible to run a supervisor without an MSFC, you just won't be routing any packets that way. Regular layer2 switching works just fine though.

Those lines are blurred nowadays too, though. The Sup720 is pretty much standard for any enterprise class chassis, and it's MSFC is part and parcel of the card (along with it's integrated switch fabric module), not an optional add-on, and it runs IOS natively. So there's no switching back and forth between CatOS and IOS like you'd see on older models.

Since the 7206vxr is a router anyway, then this MSFC cant be on this router then, as it would defeat the purpose.

Like I said man, I think you probably got some model numbers crossed. I used to work for a cisco reseller, so I got fairly conversant with how Cisco numbers things, but it gave my head a spin up until I did get used to it hehe

Chris Knight · August 2008

Ok guys, I figured somethings out after I had my morning coffee

Ok the MSFC I was referring to, was on a WS-C6509 chassis, with a supervisor card

The 7000 series is what is doing our "intervlan routing"

So since I have now figured this out, for the record the MSFC is what is doing the routing for this 6509 chassis, which can switch packets in hardware....

Wow I feel dumb

L3 switch PLEASE HELP

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