Are there any tools that would help detect/locate cabling issues?
I suspect I have a dodgy connection on a length of cable that runs outside my house between my (Ubuntu) desktop and my (OpenWrt) router. There's a gigabit switch between the two although I could probably reroute cables enough to bypass that if necessary.
My old desktop has been generally slow for a while, and now that I've replaced it with a new PC, with a fresh install to a new SSD, it's (very disappointingly) no better. Given that most of what I use it for uses the network in some way I'm thinking that's my next place to look.
Mark
There are hardware cable checkers, but they're either cheap (~£20) and check just continuity and wire map faults, or can test performance but cost hundreds of pounds like the Fluke ones.
You say it's an outside cable... did you terminate it yourself? If so re-terminating might help. Are there any connection points, or damage to the cable (perhaps from birds/squirrels/mice, or tight bends, underground water-logged pipes, or some such) that could allow water ingress or intermittent shorts? Does your cable get exposed to electromagnetic interference from nearby equipment? You could also look at the PSU that comes with your switch and router; sometimes they start providing borderline power. Are both ends connected to equipment plugged into the same power supply?
The easiest is probably to temporarily relocate the PC next to the router, use a different, shop-bought known-good cable, and compare.
What is it specifically that is slow? It could be a network software issue. DNS often seems the cause of slowness for me, and messed-up routes can cause issues too, or something like a duplex mismatch or mtu problem.
-- Martijn [1] http://www.maplin.co.uk/p/lan-network-cable-tester-n59by http://www.maplin.co.uk/p/lan-network-cable-tester-n59by [2] http://www.comms-express.com/products/microscanner2-cable-verifier-kit/?gcli...
On 9 Jun 2015, at 08:39, Mark Rogers mark@more-solutions.co.uk wrote:
Are there any tools that would help detect/locate cabling issues?
I suspect I have a dodgy connection on a length of cable that runs outside my house between my (Ubuntu) desktop and my (OpenWrt) router. There's a gigabit switch between the two although I could probably reroute cables enough to bypass that if necessary.
My old desktop has been generally slow for a while, and now that I've replaced it with a new PC, with a fresh install to a new SSD, it's (very disappointingly) no better. Given that most of what I use it for uses the network in some way I'm thinking that's my next place to look.
Mark
Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) 21 Drakes Mews, Milton Keynes, MK8 0ER
main@lists.alug.org.uk http://www.alug.org.uk/ http://lists.alug.org.uk/mailman/listinfo/main Unsubscribe? See message headers or the web site above!
On 9 June 2015 at 09:42, Martijn Koster mak-alug@greenhills.co.uk wrote:
There are hardware cable checkers, but they're either cheap (~£20) and check just continuity and wire map faults, or can test performance but cost hundreds of pounds like the Fluke ones.
Indeed, and I have the former...
You say it's an outside cable... did you terminate it yourself?
Yes I did. I will reterminate, although it's not really a strength of mine and I'm as likely to get it wrong this time as last time....
Are there any connection points, or damage to the cable
No, not that I can see anyway.
You could also look at the PSU that comes with your switch and router; sometimes they start providing borderline power.
As it happens it's a new switch, and the problem was there before and after changing it.
Are both ends connected to equipment plugged into the same power supply?
As in mains phase? Yes if so.
The easiest is probably to temporarily relocate the PC next to the router, use a different, shop-bought known-good cable, and compare.
Stupidly, I had thought about swapping cables but ruled it out on the basis that the length was too great, and had forgotten that the PC can be moved....
What is it specifically that is slow? It could be a network software issue.
There isn't a "specifically" - it seems to be pretty much everything. It's a quad-core CPU with 24GB RAM, and typically has one Virtualbox VM running and Chrome with a billion (ish :-) tabs open. At any given point htop shows CPU and memory usage to be fine (no swap in use, and the swap is on SSD anyway so shouldn't be such a hit anyway). I have a Virgin cable connection giving me 100Mbps to play with and if I do a speed test that gives me typically 85Mbps down, 5Mpbs up (which is about right for a Virgin connection) so throughput isn't a problem. Yet my desktop in the office, doing similar things on lower spec hardware and maybe 5Mbps ADSL on a good day, performs better. Note that for all the Chrome tabs and VM very little actual network activity will be taking place, although it won't be non-zero. Can a dodgy cable cause hardware interrupts (and if it can, can I detect them?). It *feels* like something is interrupting the CPU and I've pretty much ruled out all the local PC hardware by replacing it..
Additionally: I've had issues with the Virgin router just locking up and needing rebooting, or locking up on the cabled ethernet side but being fine on wireless. When I put a cable router in between the Virgin box and my home network, this issue seems to then start to affect the cable router. That's what made me start looking at the network initially.
Mark
On 9 Jun 2015, at 13:16, Mark Rogers mark@more-solutions.co.uk wrote:
You say it's an outside cable... did you terminate it yourself?
Yes I did. I will reterminate, although it's not really a strength of mine and I'm as likely to get it wrong this time as last time....
I rather like these: http://www.kenable.co.uk/product_info.php?products_id=3252 http://www.kenable.co.uk/product_info.php?products_id=3252 "Crimp ends are supplied with a crimp plug (body) and a separate guide plate, the Guide plate is removable from the main body of the crimp so allows you to align your cable outside the crimp plug and then slides inside the body to be crimped.". Easier to use, seems to work.
Stupidly, I had thought about swapping cables but ruled it out on the basis that the length was too great, and had forgotten that the PC can be moved....
:-)
It's a quad-core CPU with 24GB RAM,
Another thing to check might be the cooling -- possibly if the heatsink is not well connected and the cpu it gets too hot it throttles to a lower clock speed. Check your powersavings settings too to make sure you're not running below what you think you should have. But I'm sure you'd have spotted that by now.
It *feels* like something is interrupting the CPU and I've pretty much ruled out all the local PC hardware by replacing it..
It might also be worth to try booting into a live CD or two see if they perform better, which would move suspicion to the OS.
Additionally: I've had issues with the Virgin router just locking up and needing rebooting, or locking up on the cabled ethernet side but being fine on wireless. When I put a cable router in between the Virgin box and my home network, this issue seems to then start to affect the cable router. That's what made me start looking at the network initially.
Hm, sounds messy. Some googling suggests there are various folks with wired ethernet problems on their hub. Perhaps it's worth trying to switch that.
Good luck,
-- Martijn
On 09 Jun 15:58, Martijn Koster wrote:
On 9 Jun 2015, at 13:16, Mark Rogers mark@more-solutions.co.uk wrote:
You say it's an outside cable... did you terminate it yourself?
Yes I did. I will reterminate, although it's not really a strength of mine and I'm as likely to get it wrong this time as last time....
I rather like these: http://www.kenable.co.uk/product_info.php?products_id=3252 http://www.kenable.co.uk/product_info.php?products_id=3252 "Crimp ends are supplied with a crimp plug (body) and a separate guide plate, the Guide plate is removable from the main body of the crimp so allows you to align your cable outside the crimp plug and then slides inside the body to be crimped.". Easier to use, seems to work.
Look damned expensive for a RJ45 end though!
Stupidly, I had thought about swapping cables but ruled it out on the basis that the length was too great, and had forgotten that the PC can be moved....
:-)
... always remember stuff can be moved if needed!
It's a quad-core CPU with 24GB RAM,
Another thing to check might be the cooling -- possibly if the heatsink is not well connected and the cpu it gets too hot it throttles to a lower clock speed. Check your powersavings settings too to make sure you're not running below what you think you should have. But I'm sure you'd have spotted that by now.
It *feels* like something is interrupting the CPU and I've pretty much ruled out all the local PC hardware by replacing it..
It might also be worth to try booting into a live CD or two see if they perform better, which would move suspicion to the OS.
Additionally: I've had issues with the Virgin router just locking up and needing rebooting, or locking up on the cabled ethernet side but being fine on wireless. When I put a cable router in between the Virgin box and my home network, this issue seems to then start to affect the cable router. That's what made me start looking at the network initially.
Hm, sounds messy. Some googling suggests there are various folks with wired ethernet problems on their hub. Perhaps it's worth trying to switch that.
I'd be looking at switching out the virgin supplied router with something more sane like a TP-Link TL-WDR3600 with OpenWRT on it... but that's possibly just because I like to be able to run insane things on my router... (like, erm, quagga for the different routed internal networks).
In other news, Martijn, can you please send in text/plain only, otherwise all your mail goes through moderation, and I have to approve it... it's come very close to being rejected on principle a few times now ;)
Thanks,
All,
[.. big snippage..]
Just a quick follow-up to say that your comments haven't been ignored, I just wanted to test them before replying but haven't had the opportunity. Sorry I didn't reply sooner to say so.
I have some new RJ45 plugs (Kenable ones, arrived in the post this morning - I don't think a couple of pounds for 10 is particularly expensive for small quantities Brett, did you miss that there were 10 in the pack?) Hopefully this weekend I'll get to try a few things out.
PS: My main router is now a TP-Link OpenWRT router, I can't recall off the top of my head which model though.
Mark
-
Brett Parker -
Mark Rogers -
Martijn Koster