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Last week, I have experienced a strange scenario with Adtran NV3448(a router) and an ISP circuit. Adtran is a similar company like Cisco, also makes networking equipment such as Router, switches, etc.

Adtran NV3448 (a router) was attached to an ISP circuit on Eth 0/2 port with a direct connection. There is a simple configuration on the Adtran with the ISP IP as a default gateway.

ISP = 192.168.1.1/29
Adtran = 192.168.1.6/29 

When I perform a continuous ping from Adtran to the ISP IP, I am getting the following result.

Adtran-NV3448#ping 192.168.1.1 repeat 50
Type CTRL+C to abort.
Legend: '!' = Success, '?' = Unknown host, '$' = Invalid host address
        '*' = Request timed out, '-' = Destination host unreachable
        'x' = TTL expired in transit, 'e' = Unknown error
        'B' = Packet too big
Sending 50, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!*!**************************
Success rate is 43 percent (21/48), round-trip min/avg/max = 1/2/2 ms

As a part of troubleshooting, I have replaced the cable between Adtran and the ISP circuit. I have attached my laptop (192.168.1.6) to the ISP circuit and was able to ping the gateway without any issue. I attached my laptop (192.168.1.1) to Adtran Eth 0/2 port and Adtran was able to ping my laptop without any drop. Even with a different Adtran device or the port wouldn't work.

I reached out to the Carrier and they removed the firewall and Wi-Fi from their device and the issue is still pending.

Any help would be appreciated.

  • Do you see anything in the logs? How about port statistics? – Ron Trunk Sep 8 at 17:01
  • @RonTrunk There are no errors on the port and nothing specific on the log. – Jenil Shah Sep 8 at 20:23
  • Then I'd tend to agree with @Zac67 's answer. – Ron Trunk Sep 8 at 21:14
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Another theory: Possibly, the ISP router's ICMP message rate is exceeded and it ignores further echo requests from a certain point on - if all outputs look like !!!!!!!!!!!!!!!!!!!!*!**************************.

The difference may be the Adtran's (higher) and the laptop's (lower) ping frequencies. Try lowering the ping frequency.

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The adtran unit you listed has a T1 card. You mentioned using the eth 0/2 port on the adtran so I'm assuming your carrier (ISP) is providing another device that has an ethernet interface.

Based on the ping response you pasted it looks like there was significant packet loss. When you ping with your laptop you got no packet loss?

I would reconnect your laptop and let the ping run longer to see if you get any packet loss. While the ping is running you should move/shake the cables to see if it does make losses.

If you don't get any packet loss then it's safe to assume there is an issue with the adtran.

If there is another network beyond the link you are using you can setup multiple parallel pings on your laptop to determine where the loss is occuring.

If the equipment on the other end of the link is old (90's era) the ping may be marked low priority and get unreliable results. Pinging through the device to another host on the remote network will give you more reliable results.

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  • By attaching the laptop with the ISP circuit, I had a continuous ping for about 15-20 mins without any drops. However, I connected a completely new Adtran device to the ISP circuit and the same issue. The ping gets drop at the same place. – Jenil Shah Sep 8 at 20:26
  • I would connect the laptop to the adtran and see if you can either ping the adtran or the laptop and get no packet loss. I think the issue is with the adtran. Also worth testing is hooking the laptop to send traffic through the adtran to the ISP router. I expect there will be no packet loss. If this is the case it's the adtran having servicing the PING traffic in a non real-time manor. It's not uncommon and should not effect traffic passing through the device. – user2821413 Sep 9 at 21:56

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