nanog mailing list archives

Re: Large RTT or Why doesn't my ping traffic get discarded?


From: "J. Hellenthal via NANOG" <nanog () nanog org>
Date: Wed, 21 Dec 2022 15:21:03 -0600

As well if this persists you may consider disabling hardware rx/tx checksumming to see if it clears up your results. 
Some net cards can get glitchy causing this exact behavior.

GL

-- 
 J. Hellenthal

The fact that there's a highway to Hell but only a stairway to Heaven says a lot about anticipated traffic volume.

On Dec 21, 2022, at 13:58, William Herrin <bill () herrin us> wrote:

On Wed, Dec 21, 2022 at 9:10 AM Jason Iannone <jason.iannone () gmail com> wrote:
Here's a question I haven't bothered to ask until now. Can someone please help me understand why I receive a ping 
reply after almost 5 seconds?

64 bytes from 4.2.2.2: icmp_seq=398 ttl=54 time=4915.096 ms
64 bytes from 4.2.2.2: icmp_seq=399 ttl=54 time=4310.575 ms
64 bytes from 4.2.2.2: icmp_seq=400 ttl=54 time=4196.075 ms
64 bytes from 4.2.2.2: icmp_seq=401 ttl=54 time=4287.048 ms
64 bytes from 4.2.2.2: icmp_seq=403 ttl=54 time=2280.466 ms
64 bytes from 4.2.2.2: icmp_seq=404 ttl=54 time=1279.348 ms
64 bytes from 4.2.2.2: icmp_seq=405 ttl=54 time=276.669 ms

Hi Jason,

This usually means a problem on the Linux machine originating the
packet. It has lost the ARP for the next hop or something similar so
the outbound ICMP packet is queued. The glitch repairs itself,
briefly, releasing the queued packets. Then it comes right back.

Regards,
Bill Herrin


-- 
For hire. https://bill.herrin.us/resume/


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