[j-nsp] T1 alarm on loop detect

[Kevin Day]

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?

[Jeff S Wheeler]

Post by Kevin Day
Any ideas?

How about a routing protocol? This can be quite a chore when customers
are involved, especially if their CPE is unsophisticated; but it would
offer a well-understood solution to your problem.

- J

[Kevin Day]

Post by Jeff S Wheeler

Post by Kevin Day
Any ideas?

How about a routing protocol? This can be quite a chore when
customers
are involved, especially if their CPE is unsophisticated; but it would
offer a well-understood solution to your problem.
- J

Yeah, that's my next choice... I'm trying not to do that as it would
require replacing the CPE on the remote end which currently doesn't
support any active routing.

No big deal, just was wondering if I was missing an option that we
found kinda handy on the cisco side.

[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

Post by Kevin Day
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
Physical interface: t1-1/2/0, Enabled, Physical link is Up
Interface index: 140, SNMP ifIndex: 44
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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[Chris Adams]

Post by Kevin Day
Is there anything equivalent to Cisco's "down-when-looped"
configuration on a serial/T1 interface?

Can you switch to PPP? It'll take a few seconds, but when the PPP
keepalives fail, the protocol will go down.