802.1ah over legacy L2 cloud

[anazarenko]

Unfortunately I can't find a proper resource to understand if I can link 2 BEBs over current L2 core, which is not 802.1ah aware.

Will the traditional switches (like 3560, 6500) pass transparently 802.1ah frames?

[rsimoni · Accepted solution]

Hi there,

no they will not. By default Cat6500 and Cat3750 use Ethertype 0x8100.

from http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/layer2.html#wp1055118

we learn that:

'A port that is configured with a custom EtherType field value considers frames that have any other EtherType field value to be untagged frames. A trunk port with a custom EtherType field value places frames with any other EtherType field value into the native VLAN. An access port or tunnel port with a custom EtherType field value places frames that are tagged with any other EtherType field value into the access VLAN. If you misconfigure a custom EtherType field value, frames might be placed into the wrong VLAN.'

802.1ah standard uses ethertype 0x88a8.

That implies that 0x88a8 frames received on a 0x8100 port will be placed in the native vlan.

The issue arises if STP is enabled as it will detect a VLAN mismatch and block the port.

Only metro switches (and cisco 7600 with ES+ card) are able to natively support 802.1ah standard (and therefore understand and manipulate 0x88a8 frames).

For the Cat6500 a theoretical solution (I never tried that) would be to configure custom ethertype as suggested in the same page I posted above. But that should be done end to end on all transit ports.

Note that not all the modules support custom ethertypes. For the complete list look for 'IEEE 802.1Q Custom Ethertype' in the Release Notes

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/release/notes/features.html

For the Cat3750 this option is not available.

So unless you want to disable spanning tree and have the 0x88a8 in the native vlan (pretty risky I would say) you have no solution for the cat3750.

regards,

Riccardo

[judebryant]

Riccardo is correct.

Mac-in-Mac is an Advanced IP MPLS feature available on the 7600 series routers with the ES+ card.  Its also available on the new ME3800X with advanced IP code. ME3800X also supports HVPLS.

First quarter 2012 there will be an new ME3600X that will support these features as well.

Also look for the new 15.1 code for these switches as this code gives the switch a 7609 router feel.

Regards

Jude