Network problem

[MobileTechie]

I have a client with and handful of PCs on an SBS domain, connected via a Cisco SRW2024 switch.

3 of the PCs are in the same area and when all 3 of them are turned on, one of them loses its ability to get the internet. E.g. you cannot ping an external IP. You can ping all internal IPs and the router.

I thought it was just the one PC but after resetting some networking components and it working, the problem just appeared on one of the others instead.

Any ideas where to focus attention here?

 

[ITMAN]

Sounds like dhcp / dns pool problem ?
What ip / DNS do all the devices get? Is dhcp turned off on all network appliances except sbs?

 

[MobileTechie]

Sorry I should have said - I checked the IP addresses and they all get different leases from the SBS DHCP. No other DHCP servers.

When you say what DNS do they get - what do you mean exactly? They all have valid settings for the DNS server, default gateway, DHCP. ipconfig /all looks normall for all of them

 

[mjbasford]

Worth checking the wiring to make sure its not some hackjob using one cat5 for 2 drops. That can cause very interesting results sometimes.

 

[YeOldeStonecat]

When those Linksys business grade switches came out (the SRW series)...we installed a lot of those for smaller businesses back in those times. Not long after....we ran into lots of "quirks" with those switches. I've since yanked most of them out. Odd quirks like you're talking about.

I noticed increased problems with those switches when you uplinked another switch to them, especially if it was one of those little Linksys 5 port switches...the SD205 or something like that.

Bet the problem goes away for a while if you power cycle that SRW2024. And then it slowly creeps back.

Bet if you stick a nice HP ProCurve 1810-24G in there....the problem goes away.

 

[MobileTechie]

Yeah my guess is the switch. Also need to make sure there is no hub or switch common to those 3 machines before they get to the main switch

 

[Rob_NNCC]

Some old firewalls, (Think it was sonicwalls, RED units) had a per device licence. If you had too many devices, BAM, one would get cut off.