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supergeeky

join:2003-05-09
United State
kudos:3

Cisco switch into non-cisco switch, unknown initial lag

Here's the physical connection:

Cisco 2970G
one port from that goes to:
Netgear POE switch
3 ports from that go to network cameras
1 port goes to the camera recording server

The bandwidth-intensive cameras and recording server were put on their own switch cause 1) the cameras needed POE and 2) those systems will just talk to each-other all day long and rarely any desktop computer which is plugged into the 2970. No VLANs anywhere.

When accessing an IP camera from a desktop computer, that has not been accesses for a few hours, it's very slow to connect initially. If you visit it again after a few minutes it loads instantly.

Any ideas why that would be, is the Netgear switch congested? is it some kind of ARP cache issue on (which) switch?

Maybe I shouldn't complain, seeing as I caused this issue by offloading to another switch?

sk1939
Premium
join:2010-10-23
Mclean, VA
kudos:10
Reviews:
·T-Mobile US
·Verizon FiOS
My guess is that it's an ARP delay. I know that when I RDP I get noticeable delay on the initial connection, but then it's fine afterwards. This is more of a problem if your using device name rather than ip because then you also have to wait for name resolution.

supergeeky

join:2003-05-09
United State
kudos:3
reply to supergeeky
Thanks, thats what I was thinking...

I'm using the IP to connect so DNS resolution is not a factor.

Seeing as how the Netgear is not a manged switch, I can't set any static ARP or MAC entries there, plus since that's where all the traffic is constantly (to the recording server) I doubt it's ever getting flushed there.

Would adding something to the Cisco switch help (I can't think of how/what) something like multiple static MACs on the port that goes to the Netgear - I'm not sure what thats called or I'd be looking to configure.

HELLFIRE
Premium
join:2009-11-25
kudos:18
reply to supergeeky
Is the PC on the Netgear POE switch or the 2970?

If on the Netgear, traffic SHOULD remain local to the netgear, but I don't know.
Think there is a way to add a MAC address statically to a Cisco switch, but not
sure if it would do anything.

Dumb question, during one of these times where it takes awhile for the PC to
"connect" to the cameras, can you test your ICMP latency and see if you a) get
a pause as well before it resolves the IP, and b) what the ICMP latency is?

I halfway want to suggest throwing up a sniffer, but I'm REALLY hesitant to do
so with so little information and visibility into things.

Regards

supergeeky

join:2003-05-09
United State
kudos:3
reply to supergeeky
PCs are all on the 2970G

You bring up a great point; a ping to any device off of the Netgear is instant 1ms and even if I leave that ping running in the background and then try to visit a camera, the delay is still present the first time, and very fast subsequent times - I guess this proves that ARP cache isn't a factor, cause that has to work itself out before you can even ping.

I'll try mirroring the port on the 2970G that the Netgear is uplinked to and sniff it to see if I can find something interesting.

HELLFIRE
Premium
join:2009-11-25
kudos:18
reply to supergeeky
If I had $10 for everytime someone told me an application layer problem was due to the network...
Keep us posted supergeeky, I'm interested in the results myself.

Regards

flq06

join:2009-08-06
Verdun, QC
reply to sk1939
layer 2 (only) switches doesn't keep any ARP info. Most likely, you don't have enough host to respond to your ARP request, or your router itself won't reply.
You could also create a static arp entry for your camera.

cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9

1 recommendation

said by flq06:

layer 2 (only) switches doesn't keep any ARP info.

Yes they do; you just cannot see it on an unmanaged switch. Unless it's flooding every packet to every port all the time (which would make it a HUB), it does have tables of MAC's known to be on each port.

Bink
Villains... knock off all that evil

join:2006-05-14
Castle Rock, CO
kudos:4
reply to supergeeky
Capture the traffic from the desktop and post it—likely not a Cisco issue...

flq06

join:2009-08-06
Verdun, QC
reply to cramer
Of course, basic layer 2 mechanism. I was talking about ARP. Only a layer 3 switch, router, host know about ARP bindings.

aryoba
Premium,MVM
join:2002-08-22
kudos:4
reply to cramer
said by cramer:

said by flq06:

layer 2 (only) switches doesn't keep any ARP info.

Yes they do; you just cannot see it on an unmanaged switch.

Layer-2 switch has no knowledge of IP address or anything concerning Layer-3 and up since Layer-2 switch deals with only MAC addresses. Therefore Layer-2 switch maintains CAM or MAC address table which correlate between MAC address and certain switch port. ARP Table keeps correlation between IP address and MAC address which typically Layer-3 capable devices maintain such as Layer-3 switch and router.

An exception is IGMP snooping feature where Layer-2 switch is capable to snoop Layer-3 info of Multicast group in order to associate the Multicast MAC address (as a result of the Multicast group translation from Layer-3 IP address to Layer-2 MAC address) with certain switch ports where the Multicast subscribers connect.

said by cramer:

Unless it's flooding every packet to every port all the time (which would make it a HUB), it does have tables of MAC's known to be on each port.

Layer-2 switches typically do not flood packets, however they flood frames since the switches only talk Layer-2.

jh2010

join:2009-09-03
Brooklyn, NY
reply to supergeeky
is the initial connection speed slow whenyou connect your desktop directly to the NetGear POE switch? are you accessing via http or https? which Browser are you using(your Browser or AV software my be trying to lookup the reputation of the website). Is the Website downloading a JAVA app for access?

Some Webservers limit their CPU load to prevent the system from being over loaded.

supergeeky

join:2003-05-09
United State
kudos:3
reply to supergeeky
Thanks everyone, from the Wireshark capture I have determined that it was not the cameras nor the POE switch.

Rather, the webserver that serves the pages (which has, what basically equates to, embedded iframes to the camera streams) is timing out when nobody looks at it for awhile.

Apparently, I forgot how IIS running an ASP site likes to "fall asleep" if there is no site activity. It takes IIS a few seconds to start up the AppPool for that site if it hasn't served any content recently.


SomeJoe7777

join:2010-03-30
Houston, TX
kudos:7

1 recommendation

You can configure the app pool on IIS to not timeout and shutdown after 20 minutes (the default) if you want. Just make sure and set the configuration option to recycle it in the middle of the night. App pools running classic ASP are known to lock up if they don't recycle once in a while.

supergeeky

join:2003-05-09
United State
kudos:3
That's exactly what I did - thanks!

HELLFIRE
Premium
join:2009-11-25
kudos:18

1 recommendation

reply to supergeeky
said by supergeeky:

Apparently, I forgot how IIS running an ASP site likes to "fall asleep" if there is no site activity. It takes IIS a few seconds to start up the AppPool for that site if it hasn't served any content recently.

$10 please supergeeky ROTF

Glad you got it figured out though.

Regards