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ICMP Latency in LAN


                   Hi All,

Work Station - L2 Switch - L3 (Core Switch) - Firewall (ASA) - L2 Switch - Router ------Client network

We are getting very high latency in this network. Its showing 100ms ping from desktop to Router interminantly . All other applications are working fine, no delay in any service but only getting high latency in icmp.

1. No Qos configured in between.

2. No policy in firewall for icmp.very less over run found (3-4 incremental in 2-3 hrs)

3. All the firewall and network devices interfaces are fine (no CRC/error/)

4. Packet captured from firewall but no delay found for othert application traffic, even icmp traffic was also fine on that time.

5. Desktop to core ping is normal but its going high after reaching the firewall, but we have checked the firewall and every thing is normal.

Pls share some more idea for this issue.


3 Replies 3

Jon Marshall
VIP Community Legend VIP Community Legend
VIP Community Legend


If you are pinging an IP address owned by the router itself then be aware that routers can put a lower priority on these than actually forwarding packets through it.

We see similiar posts about ping response times to L3 switches and the answer is generally the same although there is an additional factor of pings to a switch being handled in software.

Is traffic from the workstation to the client network okay in terms of latency. If so, then don't worry about it. If not then yes you need to troubleshoot further.


But previously the ping response was normal , even it is normal now but sometimes frequesntly getting high latency.

Client is monitoring the network through icmp so they are suspecting network issue. But no issue found in running application latency.


If the ping to the router has a relatively high latency but from the workstation to the client network is fine then it is the router you need to look at.

As i say if the router is busy it will place ICMPs to it's own IP addresses at a lower priority.

Perhaps more features have been enabled on the router, perhaps more traffic is going through it. Is it a constantly higher latency or is it just intermittent.

Your customer should be concentrating on the end to end application latency rather than response times to ping from specific network devices.

But if you want to troubleshoot and end to end application response times are fine then concentrate on the router itself.


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