HIGH PING LATENCY TO VLAN GATEWAYS 3850

[mohammadjuber]

Hi,

Getting high ping latency to VLAN gateways which endpoint devices are working smooth.

Ping report to VLAN gateway-

C:\Users\juber.khan>ping 10.10.2.10 -t

Pinging 10.10.2.10 with 32 bytes of data:
Reply from 10.10.2.10: bytes=32 time=132ms TTL=254
Reply from 10.10.2.10: bytes=32 time=11ms TTL=254
Reply from 10.10.2.10: bytes=32 time=130ms TTL=254
Reply from 10.10.2.10: bytes=32 time=5ms TTL=254
Reply from 10.10.2.10: bytes=32 time=101ms TTL=254
Reply from 10.10.2.10: bytes=32 time=15ms TTL=254
Reply from 10.10.2.10: bytes=32 time=80ms TTL=254
Reply from 10.10.2.10: bytes=32 time=5ms TTL=254
Reply from 10.10.2.10: bytes=32 time=67ms TTL=254
Reply from 10.10.2.10: bytes=32 time=5ms TTL=254
Reply from 10.10.2.10: bytes=32 time=51ms TTL=254
Reply from 10.10.2.10: bytes=32 time=5ms TTL=254
Reply from 10.10.2.10: bytes=32 time=45ms TTL=254
Reply from 10.10.2.10: bytes=32 time=9ms TTL=254
Reply from 10.10.2.10: bytes=32 time=17ms TTL=254
Reply from 10.10.2.10: bytes=32 time=5ms TTL=254
Reply from 10.10.2.10: bytes=32 time=9ms TTL=254
Reply from 10.10.2.10: bytes=32 time=6ms TTL=254
Reply from 10.10.2.10: bytes=32 time=10ms TTL=254
Reply from 10.10.2.10: bytes=32 time=5ms TTL=254

Ping statistics for 10.10.2.10:
Packets: Sent = 20, Received = 20, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 5ms, Maximum = 132ms, Average = 35ms

Ping report to server through passing same switch.

C:\Users\juber.khan>ping 10.10.10.1 -t

Pinging 10.10.10.1 with 32 bytes of data:
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=7ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=5ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126

Ping statistics for 10.10.10.1:
Packets: Sent = 20, Received = 20, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 3ms, Maximum = 7ms, Average = 3ms

Regards,

Zuber Shaikh

[Mark Malone]

Hi
You wont get a constant good ICMP check to a switch vlan interface , reason being its not controlled in Copp so if the switch is processing any type of traffic icmp will be least preferred , a true test is to ping through the switch pc to pc or else use ip sla feature with a responder setup to get an accurate result , pinging a vlan will give not give you a guaranteed accurate result as you seen

[mohammadjuber]

Ping to PC from switch also giving same result.

3850#ping 10.11.35.103 re 500
Type escape sequence to abort.
Sending 500, 100-byte ICMP Echos to 10.11.35.103, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!
Success rate is 100 percent (500/500), round-trip min/avg/max = 1/10/430 ms

[Mark Malone]

check the interfaces your passing through make sure there are no errors incrementing like crcs , inputs etc a dodgy cable etc but it could also be the nics on the pcs if there processing traffic , the average is 10ms so its only jumping the odd time , cpus of the pcs or switch could be in play either , there are multiple reasons it can spike like that , if you want to get down to wire why its doing that you could use wireshark and track the actual packets between the src and dst as they transfer

the output earlier going through the switch is showing fine so it could be the end devices that are responding bit slow

Ping report to server through passing same switch.

C:\Users\juber.khan>ping 10.10.10.1 -t

Pinging 10.10.10.1 with 32 bytes of data:
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=7ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=4ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=5ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126
Reply from 10.10.10.1: bytes=32 time=3ms TTL=126

[Joseph W. Doherty]

When you ping to or from a switch, you're using the "control plane", which on a switch is generally handled by a low powered CPU which also treats ping processing as a low priority task. I.e. using a switch for anything beyond transit traffic does not represent how the switch is performing or representative of network latency.

What you want to do is ping between hosts that transit the switch.

[Georg Pauwen]

Hello,

on a side note, and in addition to Marks's posts, what is the uptime of the switch (show version) ? Sometimes very long uptimes can resolve in delayed responses. Rebooting the device could remedy that...

[mohammadjuber]

Switch uptime                      : 1 year, 4 days, 23 hours, 59 minutes

Can it create this issue?

[Joel Jackson]

In my opinion and experience a switch typically does not have any issues being up for years. I have many switches in our environment that have been running just fine since they were installed (and while remaining up). The reboot "might" fix your problem but it may start happening again. It sounds like the switch itself is busy doing some processing. Can you do a "show proc cpu hist" and "show proc mem sorted"? What is resource usage looking like?