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Network Latency

John Edwards_8
Occasional Visitor

Network Latency

I'm having a problem with latency on an all Procurve switched environment. I have a 4108GL with 7 fiber Gigabit ports. Each port connects to a set of 2 2524's that are stacked using the Gigabit stacking cards. I'm wondering if I need to set the 2524's to 1000Fdx instead of Auto? I'm having a problem with users accessing files from servers attached to the 4108. Any suggestions?
11 REPLIES
Stuart Teo
Trusted Contributor

Re: Network Latency

Can you upload a topology including all models and firmware versions you're using?

A "show interfaces brief" from the CLI should tell you if auto-negotiation was done correctly. You shouldn't have to nail the ports at 1000fdx if everything's behaving normal.

If a problem can be fixed, there's nothing to worry. If a problem can't be fixed, worrying ain't gonna help. Bottom line: don't worry.
OLARU Dan
Trusted Contributor

Re: Network Latency

You should set both ends of a Gbit link to either 1000FDx or Auto. There is a warning in the release notes of the firmaware regarding this setting.

The latest revision for 4108GLs available on HP site is G.07.50. Do you have it installed?
John Edwards_8
Occasional Visitor

Re: Network Latency

I hadn't checked for a firmware upgrade in the last few months, so I do need to upgrade the 4108 from 7.27 to 7.50. The 2524's are on the latest version already. I'll upgrade this weekend and see how it goes.
John Edwards_8
Occasional Visitor

Re: Network Latency

I ran the upgrade on the 4108gl, and there is no change with the latency problem. I also tried setting the speed on 4108gl to 1000FDX and letting the 2524's that connect to it auto negotiate the fixed speed of the 4108gl. When I did that I lost all communication to the 2524's. Do I need to restart the 2524's after this, or is there even a need to do this at all? Any suggestions?
Ralph Bean_2
Trusted Contributor

Re: Network Latency

John -

Not to challenge your problem statement, but how did you determine that it is a latency problem, as opposed to, say, dropped packets? I think your answer will help us give you better advice.

Regards,
Ralph
John Edwards_8
Occasional Visitor

Re: Network Latency

That's a great question! I might have taken for granted that it was a switch problem and not a workstation or wiring problem. After looking at that switch there are loads of CRC errors from 2 different ports. I'm going to research it a little further. What's happening is there are workstations that have to wait up to a minute to find mapped drives on the network.
John Collier
Esteemed Contributor

Re: Network Latency

John,

Not to tell you how to configure your network (everybody has different ideas and experiences) but here is some food for thought:

If you have two ends of a connection that are both going to be the same no matter what, why leave it up to Auto-negotiation? What is the overall benefit to everything involved?

Certain operating systems and network gear, while claiming to be highly capable of auto-negotiation, seem to have issues successfully determining the appropriate mutual speed. While that may cause limited issues on the outer fringes of the network, it can wreak sheer havoc on the core and the issues can be a real monster to track down since the issues are usually seen on the outer rim and we always start looking where we see the errors, not at the core.

I don't know the scope of your network and I have NO idea how large of a task this would be, but it seems as if you have spent a great deal of time in the troubleshooting process already. Perhaps it would be more prudent to start hard-coding the ends of the network links that are known to most likely remain static as you are chasing down errors (is that the port with the problem? -- No? -- Static it now and move on...). I would even include servers in this if it were up to me since they are likely to be in place for a long time to come.

What you should ultimately end up with is nothing but fringe devices (PC's, laptops, etc) left on Auto-negotiate with a solid core that doesn't have to worry about it any longer.


Just a thought,
John
"I expect to pass through this world but once. Any good, therefore, that I can do, or any kindness that I can show to any human being, let me do it now. Let me not defer or neglect it, for I shall not pass this way again." Stephen Krebbet, 1793-1855
John Edwards_8
Occasional Visitor

Re: Network Latency

John,
I'm with you 100%. That's the thought process that started this whole thread. I tried setting the fiber switch link to 1000FDX and lost communication with the remote switch. Any suggestions?
John Collier
Esteemed Contributor

Re: Network Latency

John,

If you set one end of the link and lost connection to the other end, then what happens when you set the other end first and work your way back? Do you still loose connectivity? What do the logs on each end of the link have to say before you change the speed? What about after (connectivity or not)? When you look at the capabilities of both devices, they will say that they are both capable but what do they auto-negotiate to if left alone? If they aren't physically out of your reach, then set the most remote one first (so you don't loose connection to the nearest one) and then set the one closest to you even if it says you lost connection. What happens then?

Sorry for not responding sooner, but I've had some family challenges and I really should be dealing with them now, but I needed a break.

Now the question might come up as to what my mental state is if I consider something like this a break, but I'll deal with that issue later ;-P~~
"I expect to pass through this world but once. Any good, therefore, that I can do, or any kindness that I can show to any human being, let me do it now. Let me not defer or neglect it, for I shall not pass this way again." Stephen Krebbet, 1793-1855
Stuart Teo
Trusted Contributor

Re: Network Latency

John,

Was both sides set to 1000fdx or just one?

When you said that the link won't come up, it is on both side or just one side?

Have you checked that 1 of the 2 fiber strands is not bad?
If a problem can be fixed, there's nothing to worry. If a problem can't be fixed, worrying ain't gonna help. Bottom line: don't worry.
OLARU Dan
Trusted Contributor

Re: Network Latency

This is the warning I was telling you about:

>>
Connectivity Note Regarding Gigabit-SX and -LX Port Settings for Links Between an HP Series 4100GL Switch and Other Switch Models:

In the HP 1600M/2400M/2424M/4000M/8000M switches, and also in other vendors' switches, the default port mode setting for the Gigabit-SX and Gigabit-LX ports is forced 1000FDx (Gigabit full-duplex). However, the default port mode for the Gigabit-SX and -LX ports in the HP 4108GL is Auto. In earlier software releases, the HP 4108GL tolerated this mismatch and allowed SX and LX links with these other switches to exist. The HP 4108GL (when running software release G.04.04 or greater) now complies with the Gigabit-SX and -LX standard that disallows linkbeat to be enabled when there is a mismatch. (The HP 4104GL, introduced with software release G.05.01, also complies with this requirement.) Thus, mismatched links between Gigabit-SX and -LX ports on an HP Series 4100GL switch and the HP 1600M/2400M/2424M/4000M/8000M switches or other switches that were formerly allowed will now fail. To avoid this problem either reconfigure the Gigabit-SX and -LX ports to Auto on the HP 1600M/2400M/2424M/4000M/8000M switches or other switches, or reconfigure the Gigabit-SX and -LX ports on the HP Series 4100GL switches to 1000FDx.
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