UDLD Layer 2 Protocol Tunneling on cat6506

[ajamua]

I am trying to find out is it possible to tunnel UDLD PDU using l2tp on my cat6506. The cat6506 has SUP720 with msfc3 running 12.2(33)SXH7 in native mode and I cannot find the syntax to tunnel UDLD. Currently we are accomplishing this by using a ISP provided cat3550. Our ISP uses this device to terminate a DS3 circuit that connects our office to our data center. Since we are connected through several, we want to run UDLD to be able to detect a loss of communication in between the devices we control.

We wanted migrate from the ISP provided cat3550 to leverage our cat6506 since it has redundant power and supervisors an the cat3550 does not. This is the configuration on the cat3550:

interface GigabitEthernet0/2

switchport access vlan 3157

switchport mode dot1q-tunnel

load-interval 30

speed 100

duplex full

l2protocol-tunnel cdp

l2protocol-tunnel stp

l2protocol-tunnel vtp

l2protocol-tunnel point-to-point udld

no cdp enable

spanning-tree portfast

spanning-tree bpdufilter enable

For some reason I do not have the command syntax on the cat6506 to configure a simulated point-2-point connection to tunnel my UDLD PDUs. Is this a feature only possible in the cat3550 code?

[lamav]

Hi:

You are right. The 12.2 SXH release of Cisco IOS does not allow UDLD PDU tunneling. It only offers STP, VTP, CDP and LLDP.

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/l2pt.html

The 3560 (and probably other Cisco Catalyst switches) also offer UDLD tunneling.

I'm not sure, though, why you would want to configure l2 protocol tunneling on your 6500 switches. The purpose of the command is to allow an interface that is configured as a dot1q tunnel port to accept L2 protocol PDUs and allow them to pass onto the other customer end. As you show, it's the SP's 3550 customer-facing switch ports that are configured as tunnel ports, not the customer switches. The customer switches are configured in the normal way as either access or trunk ports.

In other words, your 6500s are not tunneling the L2 protocols; the SP is providing the seamless L2 conenction by tunneling the packets to the other side, They have to make themselves as "invisible" as possible and not interfere with L2 protocol convergence.

If you have a trunk port on the 6506 that is connected to the SP's switch port, enable UDLD on the 6506 and it will be tunneled across to the other end.