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107703
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High latency issue in LAN....

amit.rane
Level 1
Level 1

Hi All,

This is my 1st post in this forum.

We have different vlans for different processes in our organization & all the vlans are created on core switch (Cisco 3750G). When im pinging any VLAN's gateway in our LAN network im getting high latency. This has not cause any problem in our network so far but i want to resolve this issue as early as possible. I have checked config in our L3 switch but found no issue.. have attached snap shot of IT vlan gateway........

Network Architecture :--

Machine-->Access Switch-->Core Switch-->Cisco ASA-->Packet Shaper-->Radware-->Internet Router-->Internet Link

Any Soln. on this issue? Thanx in advance.

Gateway.JPG

24 Replies 24

vmiller
Level 7
Level 7

First things first.

You need to run a traceroute that identifies every hop. At first glance it appears you have some form of asynchronous routing going on.

Thanx for ur reply.

Im getting high latency only while pinging gateway, ping response to other devices is normal (1ms). I dont think trace route will help to troubleshoot this issue. Any other soln????

Where is the source device relative to the default gateway? If its on the same switch,

then what changed in the config ?

Source machine is connected to access switch (Cisco 2960) and access switch is connected to core switch. I also tried pinging other ip in same vlan and got reply of 1ms.

Is the behavior the same from both the core and access switch ?

is this a new issue ? what, if anything has changed on your network.

I have the same problem in my network the to the SVI interface is a 500ms and to other pc and other or the same vlan is 1ms the latency is only for the default-gateway from every vlan.

Hola.

favor de confirmar si los puertos tanto del switch de acceso como el de core estan configurados como sigue:

switchport trunk encapsulation dot1q

switchport mode trunk

switchport trunk allowed vlan all

switchport trunkn native vlan 1

spanning-tree link type point-to-point

el switch de acceso debe tener un default-gateway:

default-gateway (ip address) --- esta ip address debe ser la ip address de la vlan 1 del switch core.

el switch core debe tener configurado:

ip routing

Consulta:

si desde el switch core haces ping al host conectado al switch de acceso tienes el mismo comportamiento en cuanto al ping ?

A la espera de tu respuesta.

Attn.

I ' m Sorry, no hablo español

amit.rane
Level 1
Level 1

@Roger --> didnt get u..use english lang

.

@Vincent --> its the same issue i have been facing this from last 2 days & haven't done any config changes on core switch in last 2 days.......also didnt find any issue with access switch....i guess its something related to core switch becoz when im pinging other devices in network im getting normal responsw 1ms.....

post the core switch config. lets see whats there.

here is the config,

i don't understand secondary addressess that are in the same subnet.

your ping responses indicate the variance in time is from the primary address

for a given vlan. what happens when you try and reach the internet from a device

directly on the core switch ? or the next device upstream from the core /

Hi Amit,

Can you also check the

     ping response from the L3 to machine

     ping response to L3 in any other VLAN i.e. MGMT VLAN from an L2

Cheers,

DJ

It appears that you are pinging the SVI of VLAN 167 on the core switch.

Pinging the SVI (VLAN interface) means that it is handled by software and sent to the CPU for processing; hence the delay in ping response.

If you are seeing high ping response times when pinging devices in a VLAN, then you may have a problem in the network or the switch

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