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New Member

3550 and mls

Does the 3550 do true layer 3 switching as with the 5500 and 6000 series switches with a built in rsm, in that it routes the first pkt and switches the rest or is it just a switch that has routing built in.Thanks

4 REPLIES
New Member

Re: 3550 and mls

It does Layer 3 switching, not MLS. MLS is the ability to route one switch many, whereas Layer 3 switching is the ability for a switch to switch packets to a Layer 3 address and make forwarding decisions based on it.

To implement MLS, you require a 6000 or 5000 Cat, and a 7500, 7200, 4700 or 3600 router.

hope this helps

Daniel,

Cisco Employee

Re: 3550 and mls

The 3550 does layer 3 switching in hardware, similiar to MLS on the 5500/6500. In other words, the CPU only process the first packet, the rest are forwarded in hardware.

New Member

Re: 3550 and mls

so essentially does it work like this ... 1st pkt in the flow gets routed and an entry is made in the switching cache ... after this all the pkts destined for other vlans for the same flow are switched at layer 2 ... this would be good if this was the case .

Also , in terms of performance, how do the 3550-12 's compare to the big mls switches like the 5500 and 6500's

Thanks for your comments

New Member

Re: 3550 and mls

As far as I am aware, what you are describing is MLS. The 3550 either routes or bridges. If the packet is IP with Ethernet II encapsulation, then the packet will be routed at wire-speed, if the packet is IP without Ethernet II encapsulation then the packet will be routed at standard routing speed. If the packet is a protocol other than IP, then it will be "fall-back bridged".

With MLS, the first packet is the flow is routed and the MLS-SE caches the destination and source MAC addresses for that flow. Then, when the MLS-SE sees the second packet with the same criteria as the one it just cached, it wire-speed switches the remainding packets in the flow, with no need to bother the router.

In terms of performance, is the packets are being hardware route by the 3550 then the performance will be as good as a 5500 running MLS, if they are being software routed, then it will only be as quick as a standard router

Hope this makes it clearer?

Daniel,

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