cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
550
Views
0
Helpful
4
Replies

Cat 6506 Giant frames over trunk link- please help

lmessenger
Level 1
Level 1

Hi,

I have 2 x 6506 switches that have a dual fibre trunk link between them.

On the ports that make up the link, I am seeing a very high amount of giant packets.

We are seeing an issue, where if 1 server is on switch A and another server is on switch B, they are having communication failures every so often.

The links are configured as trunks using 802.1q encapsulation.

The utilization of the link is very very low <1% at all times.

Can anyone advise as to what I could do

thanks

Lee

4 Replies 4

alagrawa
Level 3
Level 3

Hi Lee,

Can you tell us what module is being used on each switch to connect to each other? There are a couple of cosmetic bugs for giant counter incrementing incorrectly.

CSCed42859: Giants incorrectly reported on dot1q trunk with 67xx modules

CSCec62587: giants on dot1q trunk with sup720 uplink ports.

To further isolate the issue:

1. Are both the servers in the same vlan?

2. Does the issue not occur if the servers are on the same switch?

2. Is the default gateway for both servers located on the same switch?

3. Are there any other error counters incrementing on any of the ports connected to the servers or the links between switch A and switch B

4. Carry our extended ping tests from one server to the other and see if there are any ping drops when there is a communication failure.

5. Is this a new setup or has this been working before? Any changes made before this issue started occurring?

Please post the above information and we can try to investigate this issue further.

Thanks

-Alok

regards

-Alok

Hi Alok,

thanks for your reply, here are the answers to your questions.

1. Yes

2. Correct, if both servers are on the same switch, the issue does not occur

2. The default gateway for both servers is an HSRP virtual address, which resides on both switches. i.e. switch A vlan 101 = 10.1.1.2 switch b vlan 101 = 10.1.1.3 HSRP address = 10.1.1.1

3. There are no errors at all on any other ports, the only errors are the giants on the ports comprising the inter-switch link

4. I ran a ping from the Win2k server expriencing the problem to the Unix server at the time of the error, ping requests did time out at this time

5. this is a completely new setup. Installed last week-end, this issue has never been seen prior to this installation

The modules that make up the link are: WS-X6724-SFP

Hope this helps

Lee

Hi Lee,

Since they are the WS-X6724-SFP modules, you're probably hitting the cosmetic bug CSCed42859. This bug is fixed in 12.2(18)SXD.

Since the servers are in the same vlan, then no intervlan routing etc is involved and the issue does point to the link between the switches being the problem.

Does this issue occur continuously or is it occurring intermittently.

You can try trial and error... change the fiber, sfp. Try another port on the module. Try another module on the switch.

Is the issue between two particular servers only? Are there any servers connected on both switches that are not having the same issue?

Thanks

-Alok

Hi, thanks again for your help, I will check out the bug and let you know if it stops the giants being reported.

I willl try to explain a bit more as to what happens.

We have 3 x servers (win2k) that run overnight processing, this involves communication with a Unix server.

When any of the 3 servers are on a different switch to the Unix box, the processing fails.

Now, all 3 servers are on the same switch as the Unix box, and the processing works fine.

However, I have also noticed this.

On all our servers we have Compaq Teaming configured. So 1 NIC goes to one 6506 switch and the other goes to the other 6506 switch. Compaq teaming is configured so that one Nic sends a heartbeat packet across the LAN every few seconds, to check that the other NIC in the server is working.

I have noticed that, at the time of the overnight processing, there are errors in the event logs of all the servers, complaining that there is a heartbeat failure, as the heartbeat packet crosses the inter-switch link, I can only think that there seems to be a problem there.

I will try to change the fibre today and see what happens

Thanks again

Lee

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Innovations in Cisco Full Stack Observability - A new webinar from Cisco