Bandwidth Problems of Subnets in the same Vlan

[mehmethyeni]

Hi Community,

We have faced a strange problem in our customer while implementing non-cisco switches in their network. Firstly, we suspected from the switches but when we remove the newly installed switches from the network the problems still go on in cisco devices. The bandwidth when we transfer some files between vlan 3 subnets couldn't reach 10Mbps. But from any vlan 3 subnets to Vlan 1 or vlan 200 subnets, it easily reach 100Mbps.

Let me exceed the details of problems. Customer has 3 vlans and their subnets like this:

Vlan 3:

X.Y.124.0/24

X.Y.123.0/24

X.Y.121.0/24

X.Y.120.0/24

X.Y.96.64/26

X.Y.126.0/24

X.Y.96.0/26

Vlan 1:

X.Y.96.192/26

X.Y.126.0/24

Vlan 200:

X.Y.127.0/24

As you can see in the basic topology, we make our tests via winscp by transferring files. Here are some test results that we made.

SERVER	TEST-PC	Bandwidth Rate
X.Y.96.3	X.Y.96.87	8 Mbps
X.Y.96.3	X.Y.96.10	100 Mbps
X.Y.96.3	X.Y.120.200	10 Mbps
X.Y.96.3	X.Y.121.200	10 Mbps
X.Y.96.3	X.Y.96.200	95 Mbps
X.Y.96.3	X.Y.126.200	95 Mbps
X.Y.96.3	X.Y.127.200	100 Mbps
X.Y.127.201	X.Y.126.200	100 Mbps

Shortly,

Vlan 1 to vlan 200, 3 subnets --> all OK, 100 Mbps

Vlan 200 to Vlan 1,3 subnets --> all OK, 100 Mbps

Vlan 3 to Vlan 1,200 subnets --> all OK, 100 Mbps

Vlan 3 between its subnets --> problem, max 10 Mbps

Vlan 3 in the same subnet host --> all OK, 100 Mbps

What can be done in this situation?

[Ganesh Hariharan]

       Hello ,

What switch model are you using and could it be possie for you to share th interface stats what is hapein when traferring the data from PC over vlan 3 to others.

Regards

Ganeshh Iyer

[mehmethyeni]

Actually customer divided subnets to 2 vlans (vlan1 and 3) for entering the traffic to the IPS a couple years ago. When I change any subnet's vlan membership from 3 to 1, the problem seems resolved. Another interesting thing  is that when I disable IPS, problem still goes on unless I change subnet's vlan. Finally, I have to manage IPS in another way.

Thank you,

[Ganesh Hariharan]

Mehmet Halil Yeni wrote:
Actually customer divided subnets to 2 vlans (vlan1 and 3) for entering the traffic to the IPS a couple years ago. When I change any subnet's vlan membership from 3 to 1, the problem seems resolved. Another interesting thing  is that when I disable IPS, problem still goes on unless I change subnet's vlan. Finally, I have to manage IPS in another way.
Thank you,

It would be helpful if you can represent in diagramatic presentation what exactly is issue is ....

[Hari Haran S M]

Hi Mehmet,

Where is the intervlan routing? I see that you have different subnets in vlan 3. How is the routing between these subnets?

Regards,

Hari

[Alessio Andreoli]

HI Mehmet,

what about the duplex settings? How did they negotiate them? Try to hardcode the speed and the values and to disable DTP.. After this check the CRC on the interfaces..If this issue persist it probably would be a good idea to re-configure the broadcast domains and/or to tune them

Hope this helps

Alessio