Re: Trunk on Cisco SG300 Switch constantly removing ports and ad

Vishal.Seetal · ‎03-20-2012

Hi all,

I have a Cisco SG300 switch on which trunks are configured. I have a server which sits on the switch via a trunk link of four network cables (4 Gbps total)on which LACP is enabled. I'm having trouble connecting to the server using VNC from a computer on the network. It doesn't happen all the time though, it's just random. On looking at the logs of the switch, I saw something unusual. The trunk that connects the switch to the server is constantly removing all the member ports and adding them back again after a few minutes interval. That causes the trunk link to flip on and off all the time. What could be the reason that's causing it to happen?Has anyone come across this issue before?

I know it could be the network cable but I'm using brand new cables and the server also is brand new.

Please have a look at the following screenshot of the logs on the switch:

Any help would be greatly appreciated.

David Hornstein · ‎03-21-2012

Hi Chundunsing,

A few questions that come to my mind.

I would make sure that you have the most up to date, NIC card firmware drivers for your server.
Make sure you are using minimum firmware 1.1.2.0 on the switch

Have you set up link aggregation with LACP on the server, please describe what you setup on the server ?

Can you reply maybe with a URL reference to the manual, that describes how to setup Link aggregation with LACP on the NIC cards ?

I am working on a assumption that LINK aggregation with LACP is not configured correctly on your server and or Switch.

I would ask a network knowledgeable colleague to double check your server setings as well as the switch settings. It's good doing that, as you can sometimes miss something simple, that they might spot immediately. Happens to me all the time.

I am wondering if a protocol like spanning tree may on the server may be blocking the LiNK aggregated ports, as my ports seem to be dropping every few seconds..

When in cli mode of the switch, can you capture and attach as a file with the the result of ;
- show tech

regards Dave

Vishal.Seetal · ‎04-07-2012

Hi Dave, Thank you so much for your response and I am really sorry that I missed your email. It's only today that I saw your email. I actually still need some help and I would really appreciate if you could get back to me with your or your network engineer contact details so that I can contact you. I really appreciate your last call which was around February of this year. I have had two major issues recently with my network setup. First is, on two occasions, the network slowed down. It didn't slow down to a crawl but it did show signs of something very wrong. A look at Wireshark captures showed many bad checksums only for outgoing packets leaving the computer on which Wireshark is installed . I read the FAQs from the Wireshark website which states that this might be caused by checksum offloading whereby checksum is not done on outgoing packets. So, I disabled checksum offloading on the NIC settings and enabled checksum on Wireshark. This didn't change anything. I still see many checksum errors on outgoing packets.I have seen this when running Wireshark from several computers. Another major issue is that the redundant switch at the core level (I have two switches at the core level in a redundant set up) constantly started forwarding and then blocking every few seconds after I rebooted it. This happened even STP was set up on the switches. It may be that I missed some configurations. I would really appreciate if someone could have a look at the configurations on the switches or servers. I have seven of the Cisco SG300 switches on the network, two at the core level and five at the access level and we are going live in a week or so. I really need help. I will send you the switches configs and more details on Monday, the 10th of April 2012. Once again I apologize for having missed your email ealier and I would like to solicit your help in resolving these issues. I am looking forward to a reply from you very soon. Best regards, Vishal Mobile: 0431130599Work: (02) 82051000

Date: Wed, 21 Mar 2012 08:48:02 -0600

From: supportforums-donotreply@supportforums.cisco.com

To: vishal90216@hotmail.com

Subject: - Re: Trunk on Cisco SG300 Switch constantly removing ports and adding them by itself

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Re: Trunk on Cisco SG300 Switch constantly removing ports and adding them by itself

created by David Hornstein in Small Business Switches - View the full discussion

Hi Chundunsing, A few questions that come to my mind. I would make sure that you have the most up to date, NIC card firmware drivers for your server.Make sure you are using minimum firmware 1.1.2.0 on the switchHave you set up link aggregation with LACP on the server, please describe what you setup on the server ?Can you reply maybe with a URL reference to the manual, that describes how to setup Link aggregation with LACP on the NIC cards ?

I am working on a assumption that LINK aggregation with LACP is not configured correctly on your server and or Switch. I would ask a network knowledgeable colleague to double check your server setings as well as the switch settings. It's good doing that, as you can sometimes miss something simple, that they might spot immediately. Happens to me all the time. I am wondering if a protocol like spanning tree may on the server may be blocking the LiNK aggregated ports, as my ports seem to be dropping every few seconds..When in cli mode of the switch, can you capture and attach as a file with the the result of ;show tech regards Dave

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Start a new discussion in Small Business Switches at Home

Vishal.Seetal · ‎04-09-2012

Hi David,

I wanted to give you an update of the issue I am having in my network. Well, it seems that the network loop was caused because the of a faulty link in one of the LAGs configured on the switch. What I observed is that the faulty link caused the trunk to flip between forwarding and blocking for about two hours before it went down. During this two hour period, the redundant core switch also went into blocking and forwarding flipping wich I presume is because the other core switch was flipping between forwarding and blocking states.

But now this raises other questions: Can a faulty link which is a member of a LAG cause the latter to flip between forwarding and blocking? And does the switch shut down a port if it finds that the link associated with that port is faulty?

I'm thinking I could have missed a configuration. I would really appreciate your help to get someone to double check the configs on the switches.

Thank you.

Kind regards,

Vishal

Date: Wed, 21 Mar 2012 08:48:02 -0600

From: supportforums-donotreply@supportforums.cisco.com

To: vishal90216@hotmail.com

Subject: - Re: Trunk on Cisco SG300 Switch constantly removing ports and adding them by itself

Home

Re: Trunk on Cisco SG300 Switch constantly removing ports and adding them by itself created by David Hornstein in Small Business Switches - View the full discussion

Hi Chundunsing,

A few questions that come to my mind.

I would make sure that you have the most up to date, NIC card firmware drivers for your server.

Make sure you are using minimum firmware 1.1.2.0 on the switch

Have you set up link aggregation with LACP on the server, please describe what you setup on the server ?

Can you reply maybe with a URL reference to the manual, that describes how to setup Link aggregation with LACP on the NIC cards ?

I am working on a assumption that LINK aggregation with LACP is not configured correctly on your server and or Switch.

I would ask a network knowledgeable colleague to double check your server setings as well as the switch settings. It's good doing that, as you can sometimes miss something simple, that they might spot immediately. Happens to me all the time.

I am wondering if a protocol like spanning tree may on the server may be blocking the LiNK aggregated ports, as my ports seem to be dropping every few seconds..

When in cli mode of the switch, can you capture and attach as a file with the the result of ;

show tech

regards Dave

Reply to this message by going to Home

Start a new discussion in Small Business Switches at Home

Vishal.Seetal · ‎04-09-2012

Hi David,

It's me again. Just one thing, the firmwware on the switches are version 1.0.0.27. Will it be a big difference if I upgrade the firmware on the switches? Are there many bugs in the version 1.0.0.27 which are fixed in the version 1.1.2.0?

Thank you for your kind recommendations.