PCs on Same Switch Cannot Connect to Each Other

[enjay]

I'm trying to share a printer out across a few rooms, and failing. After much faffing around, it transpires that devices on that switch cannot connect to - or even ping - each other. They can ping devices elsewhere in the school, and devices elsewhere can ping them, but they seem unable to ping each other.

 

We have other switches of the same model which are unaffected by this; it may be important to note that the affected switch has VLANs configured onto it.

 

Any suggestions?!

[oalcock]

Do you have DHCP running? Have you a spare switch to test? Have you tried changing the ports on the switch that both workstations and then trying then?

[enjay]

DHCP is running, but the PCs appear fine in both that and DNS.

 

I do have a spare switch, but not one which could take the VLAN, so I don't really want to swap that out. I do have the same model of switch elsewhere (without the VLAN) and things are fine on that.

 

Thinking about it though, I don't think the VLAN is the cause of the issue, as devices on the other VLAN can connect to each other.

[robk]

That sounds like some form of port isolation mode, like you would use on public wireless or hotel ethernet? What sort of switches are they?

[enjay]

That is plausible actually, robk. The VLAN is to support an open-access WiFi for the Sixth Formers, but is on the same switch as some schools PCs, so we've locked the access down a bit. Would that stop devices from pinging each other?

 

The thing is, laptops on the "open" VLAN are able to access a printer on the "school" VLAN, so I don't see why two PCs on the same VLAN can't see each other.

[SYNACK]

This could also be firewall based. Are the computers domain joined and if so is group policy set to allow file and print along with managment traffic and ping from the subnet in that VLAN. If it is a new one this may have been overlooked and so a station in that segment may not be able to talk to another in the segment as that subnet does not have an allow set in the firewall.

[enjay]

File and Print Sharing is enabled on the network adapters, Windows Firewall was turned on but turning it off doesn't help. These computers aren't in the VLAN, they're in the regular LAN (or are both the LANs considered to be VLANs?)

[SYNACK]

If they are in segregated lans partitioned by the VLAN feature of a switch or group of switches then they are considered VLANS. If they are wired into completely seporatly cabled and switched networks segregated by an 'air gap' then they are individual LANs.

 

If turning off the firewalls did not work then it may be some form of port segregation turned on somewhere in the switch config but that usually requires some rather hefty layer3 gear somewhere in the network to pull off based on swich ports alone.

[Guest TheLibrarian]

Off topic and something you are probably already aware of but just in case, there is a 10 connection limit to shares on NT/2000/XP/Vista/Win7 (probably on W9x and WME too).

[enjay]

I'll have a look at the switch management and see if I can see any of this port segregation.

 

I did know about the 10 connection limit (although I think it is 11, not 10), but that isn't applicable in this instance, as this is the only PC attempting to access this printer.

[cpjitservices]

I'd look at the routing between the VLANS, if that switch isnt on any VLANS and the rest of them are then that could cause issues you may have to set static routes in your router so that the switch knows where to send the traffic,

 

It looks to me like a VLAN issue I Have seen this before - a switch without VLANS connecting to switches with VLANS it caused problems because the switches weren't sure where to send forward traffic.

 

Double check that your switch hasnt got a Default VLAN - usually VLAN1, this can also cause issues between other switches and other VLANS, if one switych is using VLAN one and other switches are using VLAN 1 only for management then it's not going to work - also have a sneaky peak at Spanning-Tree (STP) that could be blocking something ?

 

Are your switches stacked and what make are they ? IF it's not a VLAN Issues I'd check the subnets of the PC's and the default gateway just to double check everything is ok then if everything is OK i'd change the wireless into its own VLAN and the PC's on the same VLAN because you know that VLAN works and just lock it down a bit and watch the traffic, save the configs power down the switch, power it back up and restart all the hosts.

 

EVerything should be fine

[enjay]

Okay, VLAN it was - for some legacy reason, the port which the guest PC was connected to was on VLAN1 and the host PC was on VLAN2. This enabled them both to access the main network but not each other.

 

Thanks folks.

[cpjitservices]

Glad to be of help, I'd seem this before with default VLANS they can play with your mind

 

 

CHris.

[enjay]

I'd pretty much forgotten about the VLAN on that switch - it is there for a wifi hotspot in the Sixth Form which IT Support don't really get involved with. We produced a document saying how to connect and explaining that the students are on their own with connecting to and using it. I guess my "set it up and walk away" philosophy was a bit too effective in this instance!!

[cpjitservices]

Don't worry about it, I'm sure in our hast do other things more important we have all tried to leave things to other folks but things never seem to go that way.

 

Glad you up & running now.