Multilayer Switching

[daniel.bowen]

I have a Catalyst 5500 with an integrated RSM. I have the supported hardware and software. We utilise VLAN interfaces on the RSM and have a VTP domain of "Joe". Could somebody please help me with the commands needed to configure MLS and anypossible pitfalls?

Also, is it necessary to configure a management interface on the RSM?

Thanks very much in advance

Daniel,

[DALE FRANCIS]

Daniel,

How you doing, you spend a lot of time on this forum.:))

MLS is pretty straight foward to configure, there are some limitation for multicast traffic etc but none that you should be too worried about.

The crucial thing when confiuring MLS (which i found out the hard way) was to insure you place the VTP command on the interface before enabling MLS on that interface.

There is an initial VTP domain under MLS called "NULL" and if you do not put the VTP domain on the interface 1st it will remain under this domain.

The maximum MLS cache size is 128K. However, an MLS cache larger than 32K increases the probability that a flow will not be switched by the MLS-SE and will get forwarded to the router.

The Cache can be contrained by configuring access-list and attaching these to the flow-masks.

The flow mask is based on the access lists configured on the MLS-RP interfaces. The MLS-SE learns flow mask via the Multilayer Switching Protocol (MLSP) messages from each MLS-RP for which the MLS-SE is performing Layer 3 switching.

NB!! Layer 3 switching is not possible because MLSP is not supported over FDDI and Token Ring media.

Also bear in mind that MLS is a two stage process, the candidate packet (1st packet to traverse MLS) is sent through, then the enabler packet (Back to source) completes the entry.

This wil help you configure.

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/layer3/mls.htm

[daniel.bowen]

I am fine thanks.

Thanks for the advice, will get this configured now.

Do you understand the theory behind the management interface? I have read details that for each VLAN configured, a management interface also needs to be configured.

Is this true?

Thanks again,

[DALE FRANCIS]

Daniel,

You only need to configure one interface as the management interface, this is typically the SNMP interface used for Net Managment. The management interface is what MLS uses to communicate MLSP between SE and RP as far as i know and have debugged.

Regards

[daniel.bowen]

I want to enable MLS for interfaces VLAN2 and 3. Both of these are IP and IPX interfaces and are not used for Net Management. Can one of these be specified or will it have a performance hit?

Thanks again for your help !

[DALE FRANCIS]

Go ahead, there should be no hit.. :))

[daniel.bowen]

Just one final question I promise !!

if I do not specify a management interface, will one be selected by default (the one with the lowest VLAN id)?

I have read conflicting Cisco documents !

[kmuthukamu]

If we don't specify any management interface and no other vlan except vlan 1 , then

vlan 1 will be the management inteface.

If we don't specify any management interface and configured some vlans, it will take

the lowest id vlan.

But it's always recommended to specify the managemnet interface to troubleshoot the problem easily

[daniel.bowen]

Thanks very much !