[j-nsp] T1 alarm on loop detect

[Krishna K. Verma]

Hi Kevin,

I don't think "down-when-looped" option is available for T1 interface in 
JUNOS. This option is being used in Cisco IOS, when an interface has a 
backup interface configured. It is needed for backup interface to be 
enabled when the primary interface is either down or in loopback. By 
default, the baclup is only enabled if the primary interface is down.
By using the down-when-looped command, the backup interface will also be 
enabled if the primary interface is in loopback.

I will appreciate if you could send more configuration detail of T1 
interface and Smartjack. 
When T1 interfce at Juniper side detects remote loopback, it marks 
Device flags with "Loop-Detected". At the same time, it brings the 
logical interface (ifl) down, but physical link will remain up.

I am not sure under which condition smartjack triggers "loopback when 
unavailable". Does it look for layer one error only ?

Thanks,
KK



Kevin Day wrote:

>Is there anything equivalent to Cisco's "down-when-looped"  
>configuration on a serial/T1 interface?
>
>We've got a T1 that pretty frequently goes down, but when it dies it  
>falls into loopback at the smartjack. It will appear like:
>
>Physical interface: t1-1/2/0, Enabled, Physical link is Up
>   Interface index: 140, SNMP ifIndex: 44
>   Link-level type: Cisco-HDLC, MTU: 1504, Clocking: Internal, Speed:  
>T1, Loopback: None, FCS: 16, Framing: ESF
>   Device flags   : Present Running Loop-Detected
>
>However, the only things I seem to be able to trigger an alarm on are  
>AIS and a Yellow alarm, neither of which happen during an outage like  
>this.
>
>Other than just triggering an alarm, I'd also like a lower preference  
>route to kick in, but that also doesn't seem to be happening because  
>it thinks the interface is still up.
>
>AT&T is saying that "loopback when unavailable" is their new default  
>configuration for smartjacks, because it makes troubleshooting easier  
>for them.
>
>Any ideas?
>
>
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