ASR - 9000 <---> ME 3400 Unidirectional Link detection

[amunoz]

Hi,

I want to configure a UDLD  l in link between  asr 9000 and ME 3400, but i thint that it is not supported in ASR 9000, then  i am configuring ethernet OAM,

in two sides.

When i disconnected TX fiber of 3400, the  asr 9000 sends OAM message and the ME 3400 put the port in err disable status,  thats OK,

but in the opposite way  it doesnt work,  the 3400 dont  send packets when y quit the tx fiber in 9000 side,  i read  in 3400 documentation that 3400 dont send  Link Fault OAM BPDUs.

Then how i can do it? i mean, that the port in asr 9000 shut down in one way comunication case?

thanks

[Ricardo Suarez Gamez]

Hi Adrian

I have the same problem with those two equipments. Unidirectional fiber cuts occurs some times on my network, and I need a mechanism that would trigger flex link and LAG protocols on those situations.

Hopefully somebody would help us both on this topic

Sent from Cisco Technical Support iPhone App

[tnothnag]

Hi Ricardo & Adrian,

the ASR9000 does not support UDLD and there is currently no plan to implement it.

Starting from IOS-XR 4.0 Uni-direction Link Fault detection (UDLF) is supported , which is a feature of 802.3ah OAM.

However, the ME3400 can process the Link-Fault packets, but cannot generate it, which explains the outcome of Adrian's test.

http://www.cisco.com/en/US/docs/switches/metro/me3400/software/release/12.2_58_se/configuration/guide/swoam.html#wp1109557

Looking for an alternative for failure detection, you might check for BFD

http://www.cisco.com/en/US/docs/switches/metro/me3400/software/release/12.2_58_se/configuration/guide/swiprout.html#wp1414859

Hope that helps,

Tim

[Ricardo Suarez Gamez]

Thanks Tim:

The thing is that I am using ME3400 & ME3400E as pure Layer 2 mode (Carrier Ethernet UNI device), so BFD wont work there

- BFD is not supported on Layer 2 interfaces, pseudowires, static routes, or port channels.

- Although you can configure BFD interface commands on a Layer 2 port, BFD sessions do not operate on the interface unless it is configured as a Layer 3 interface (no switchport) and assigned an IP address

I've been trying with common Autosense=ON on both links member of a LAG (work+stby) group (ME3400 with common LAG, then 2 ASR9K with MC-LAG). In that case unidirectional failure does shut down the whole port and LAG goes to the protection link (around 80ms of service disruption which is ok). Nevertheless when I reconnect the primary link again I have a service disruption of 2 or 3 seconds when LAG goes back to its initial state

I will try the same with Flex link to see what happens there.

Any other idea to get a minimum service disruption with LAG and Felxlink when unidirectional failures occur? As TE FRR and OSPF Fast Convergence can do that work into MPLS domain I suppose it should be something as good as that into Layer 2 (access) domain

Regards

Ricardo

[tnothnag]

Hi Ricardo,

I would not look for any other solution. On top of my head I do not have

any further idea.

In my opinion, it needs to be determined, why there is a 2-3 second

outage, when the primary link recovers. I do not have an explanation for

this right now. The default behavior is, that there is no revert to the

primary link and the secondary link should stay active.

Once this is sorted out, this seems to me like the most practical solution.

For a small check, you may post the related config and mention the used

IOS(-XR) releases.

If you require a deeper analysis, it might be worth to open a TAC case

for it.

Regards,

Tim