OC3 Up/Down only when moved

nathanieljhnsn4 · ‎10-01-2015

I have one I can't figure out. We're in the process of upgrading from 7206 routers to ASR 1004. When moving POS fiber cable to new ASR, the interface goes up/down. It's got the correct settings which I'll post below. We've tried replacing the fiber cable, but that doesn't seem to work. When we move the cable back to the old 7206, it doesn't go up/up immeditaley either. We have to re-seat a few times. Anyone ever seen this before? As I said we've replaced the SM fiber as the old looked bent at one point in the run. Telco sees alarm coming from CPE, looks good to the demark. We thought about replacing the OC-3 card the circuit is on, but I don't buy it cus there's a circuit from a different carrier on the same card on a different port that has no issues and goes up/up.

Note that each circuit has tons of CRCs, runts, and errors as I'd expect on a turnup, but the circuit in question also has giants.

ASR - POS0/1/1

ip address 10.250.12.130 255.255.255.252

encap ppp

crc 32

pos scramble-atm

POS4/1 is up, line protocol is up
Hardware is Packet over Sonet
Internet address is 10.250.12.130/30
MTU 4470 bytes, BW 155000 Kbit/sec, DLY 100 usec,
Encapsulation PPP, LCP Open
Open: IPCP, crc 32, loopback not set
Keepalive set (10 sec)
Scramble enabled

7200 - POS4/1

POS4/1 is up, line protocol is up
Hardware is Packet over Sonet
Internet address is 10.250.12.130/30
MTU 4470 bytes, BW 155000 Kbit/sec, DLY 100 usec,
Encapsulation PPP, LCP Open
Open: IPCP, crc 32, loopback not set
Keepalive set (10 sec)
Scramble enabled

Leo Laohoo · ‎10-01-2015

Note that each circuit has tons of CRCs, runts, and errors as I'd expect on a turnup, but the circuit in question also has giants.

Giants, I get. CRC? That's a Layer 1 issue. If the fibre optic cable has been replaced then check the terminating ends.

nathanieljhnsn4 · ‎10-07-2015

Agreed. Cleaned the fiber on both ends. Ending up being a protection issue on the card(s). Hard Loop to the SP brought it back up/up.

Tom Randstrom · ‎10-05-2015

I've seen unstable links when a singlemode interface card is patched through a multimode jumper. Link may operate when the jumper is secured and not moved, but can fluctuate widely during jumper movements.

nathanieljhnsn4 · ‎10-07-2015

Thanks for the assistance folks! Found out the issue after a painful 2 hour phone call with the SP. So whenever we moved the fiber from the 7200 to the ASR, the link would go up/down and stay up/down even if we moved it back. I spoke to the tech who informed me that when he tried a new SM LC/FC cable, same results. When he tried the old one again, it went up/up. That was the first instance. Second time around, this didn't work. We reloaded the router and it went up/up. Third instance neither worked. So we started thinking the OC-3 card in the MUX was bad. Before we could send a tech to replace it, the SP did some investigating and put a loop in Customer Prem to them. In doing so, our link went up/up!

Came to find out that the protection card is either defective/couldn't failover from the secondary protection path. i.e. Whenever the cable was move, it would trigger protection saying "hey! you guys are down! I'm gonna put you on the secondary path!". Problem is lack of path/defective card, SO we were stuck in a hung state! Turning on that loop basically reset/force it back on the primary path. So going forward we know not to move that cable until a protection solution is rectified. Write that one down!

nathanieljhnsn4 · ‎10-07-2015

I should also note (again, our problem to fix on the protection side) we had a similar issue years back with a DS3 going to a 7200. Had thought that maybe the BNC was loose, so I reseated it. Still was up/down. I put a softloop on the router via the interface cli and turned it off. Boom, line went up/up.