ping enables communication by time..

[Sebastian Helmer]

Dear all,

I'm facing a strange problem and checked already a lot but maybe u will give me some good addittional thoughts.

We have a server in an openstack enviroment virtually running quiet fine. After a while, today it was after 72h, sometimes after eben less (24h e.g.). The External SAP ist not able to connect to that Servers DB to pull the data.

When I ping the SAP from that DB Server, SAP is again able to pull immediately..

I have a small business switch SG550xg between Openstack and network. The problem I'm not able to check the customer network means router and SAP cloud connection.

Before where the DB was baremetal installed, it was working quiet fine, but also there we hade the application server and DB server on the same system. Now it is separatet...

I expect ARP issues, but don't really imagine why..

I guess it can't be a routing issue..

maybe a state issue on the customer firewall, but why is ping triggering the state for another protocol.

with the ping I was able to have a stable situation for days..

maybye you have some good thoughts..

cheers,

sebastian

[Georg Pauwen]

Hello,

the first thing you want to check when you have a 'weird' issue with these small business devices is to check if you are running the latest firmware, which for the SG550X is release 2.4.5.71.

The SG550X lets you specify static MAC addresses, you might want to try that (page 236 of the attached guide):

https://www.cisco.com/c/dam/en/us/td/docs/switches/lan/csbms/350xg/admin_guide/AG_Tesla_350_550.pdf 

[Sebastian Helmer]

Im running the prior latest code, but we are planning to change that soon.

I don’t want to use static entries because it’s an virtual environment and the sever could move to another node if necessary. And i don’t understand why this happens after hours and not the common aging time...

[paul driver]

Hello

what makes you think this is a network issue and not a server one?

it could be that for some reason these server nics go into a hibernation mode have you checked for that?

[Sebastian Helmer]

Thanks but the power management is disabled in that NICs the option is not available on the NICs.

[paul driver]

Hello

so just to clarify the application server which is the sap and DB server were on the same system but now they are separate and since then your experiencing intermittent connection problems?

have you been able to capture the traffic between these to servers? 

What does the interface statistics show for these devices? 

[Sebastian Helmer]

I wasn't able to capture the traffic yet but we plan to make that possible...
Before the SAP was always in another Segment, but the DB Server was not virtual it was a HW Server.

[Richard Burts]

The topology here is not clear to me. You describe a server and an external SAP. Can you clarify how they are connected and which parts of that connection you have visibility to and which parts you do not?

The symptom of failing connectivity which is resolved when the server pings the SAP suggests that something is timing out which prevents access from SAP to server and is restored when server pings SAP. Perhaps it is an arp entry or perhaps a mac address table entry?

HTH

Rick

[Sebastian Helmer]

Yes, I expect an arp issue as well, but not sure how to explain that. I can only look on the L2 Level, the Routers are already customer stuff and I plan to invite him to support us..
That's the way:
Traffic to SAP (VPN):
Server - (R1 - Firewall) - SAP
Traffic to Internet
Server - R2 - Internet

I don't know why and I think we should change that because there is no need to use different routers, with host routes on the window, but it was done in the past..
I can't explain why there could be an arp issue in that a-sync routing scenario..

[Richard Burts]

The mention of VPN is interesting. Can you tell us more about it? Is it possible that the VPN is configured in a way that requires that the VPN be initiated from your end and not from their end? (That can be the result when one of the VPN peers has a dynamically assigned IP address and there are some other reasons but dynamic IP is probably the most common)

HTH

Rick