Windows – Ping only works after about 30 seconds

cisconetworkingpingroutingwindows

Today I am working on this issue and I would love your ideas.

There is a network with something like this

LAN 1 — WAN CHANNEL— LAN 2

The LAN 1 have two segments.

When I make a ping from LAN 1 segment 1 it works like a charm.

When I make a ping from LAN 1 segment 2 I have no ping, but after about 30 seconds of continues ping (ping -t) it start to work perfect. After some time of no activity with the destination host the issue happens again.

Tracing the route packets stops in the last router before the target. This is the first router in LAN 2 after the WAN channel.

In the next screenshot you can see thie issue, the first ping is before a continuos ping and the second one is while continous ping is running.

enter image description here

Thank you in advance

Best Answer

This can sometimes happen if a ping is crossing a network security device. In some cases, pinging by DNS name will trigger a URL filter in a UTM device. It may take several seconds to get a positive or negative response which cases a delay in ICMP. Once a positive response has been received, then future pings are allowed until a timer expires. That logic depends on how the security policy is set up.

So why would segment 2 be affected and not segment 1? In this theory, it's a rather simple matter of different policies for different segments. Perhaps there is an intentional difference in some kind of security context that is having unintended consequences.

Troubleshooting steps:

  1. Ping LAN 2 from your gateway device itself. See if you can ping from the device using a Segment 2 context.
  2. Capture traffic from both the pinger and pingee, then compare dumps. See how long of a delay there is between when the pinger sends and the pingee receives. If it's mere milliseconds, then there's something wrong with the return trip. If it's 30 seconds, then some device in between is holding the traffic.
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