I have a Cisco 2960g 48-port switch. I've determined ports 25-28 are not functioning properly. Here is what works:
-I can get a DHCP address -I can ping to/from a workstation connected to these ports. -I can ping machines on the internet -I can telnet from these ports to machines on my LAN.
Here is where it fails:
-I cannot access any windows file shares on other workstations in the domain -I cannot establish HTTP connections to web sites (no web browsing).
The strange thing is that this is a layer 2 switch, and all my symptoms point to a layer 4 or above problem. But why is the problem specific to these ports?
I've checked the following on the switch:
-all ports are on the same VLAN (1). -Problem ports 25-28 have no input, output, frame errors, etc. All 0. -Tried issuing shut and no shut on the ports and it didn't help. -port counters look normal. Everything looks normal from the switch's perspective.
The only thing I haven't tried is a switch re-boot (it's in production).
Anyone have any ideas or suggestions?
Thanx Karl
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I don't see anything in the config that would cause your issue. It makes me suspect something on the computers connected to those ports. Did the computers on those ports work OK previously? Just for the heck of it, if you haven't already done so, unplug the cable for one of your workstations that are able to fully access everything and plug that cable into one of the suspected ports and see if that computer then experiences the same problem.
Yeah, well here's the strange thing. I initially went under the assumption that it WAS the computer, until I tried plugging several working computers into the 4 problem ports, and much to my surprse, I saw the same behavior. In fact, that's how I found the problem ports, since the switch gave me no indication of any errors. I tested each port manually on the switch until I identified the 4.
will allow a computer to connect but their frames are dropped. Thus you will get a link light, but you can't pass frames.
If the switchport port-security maximum is 1 with the switchport port-security mac-address sticky
then any comp that connects that isn't the original one, frames will be dropped but you will get a link light.
If the running-config was not copied to the startup-config, you can reboot and the whole config is wiped. If it's been copied, then your out of luck. You can copy this config to a TFTP server, reboot and reload run-config from TFTP or make the switch look for a TFTP server to load a run-config so you can test your config, reload the old one.
note: the switch by default will allow all frames to be sent, so if you wipe out your config, you probably only lose the switchport security config,
If port security was causing frames to drop I don't think he would be able to ping and telnet from those ports as he said in the original post. That's what is wierd about this. Makes you think huh?
Edited to add: You can check to see if there are any violations with the command: "sh port-security"
I think I would setup a monitor session with one of those ports as the source and run a sniffer while you try to hit a web page from the computer on that port and see if that gives you any clue as to what's causing the problem.
Interesting. Did a show controllers on port 25 and the thing that jumps out immediately is the high number of FCS errors (1591). Could this be a defect in the switch?
------------------------------------- Transmit GigabitEthernet0/25 Receive 1857575 Bytes 696358 Bytes 2815 Unicast frames 2898 Unicast frames 1573 Multicast frames 62 Multicast frames 3839 Broadcast frames 79 Broadcast frames 0 Too old frames 679749 Unicast bytes 0 Deferred frames 7426 Multicast bytes 0 MTU exceeded frames 9183 Broadcast bytes 0 1 collision frames 0 Alignment errors 0 2 collision frames 0 FCS errors 0 3 collision frames 0 Oversize frames 0 4 collision frames 0 Undersize frames 0 5 collision frames 0 Collision fragments 0 6 collision frames 0 7 collision frames 761 Minimum size frames 0 8 collision frames 1283 65 to 127 byte frames 0 9 collision frames 557 128 to 255 byte frames 0 10 collision frames 61 256 to 511 byte frames 0 11 collision frames 247 512 to 1023 byte frames 0 12 collision frames 130 1024 to 1518 byte frames 0 13 collision frames 0 Overrun frames 0 14 collision frames 0 Pause frames 0 15 collision frames 0 Excessive collisions 0 Symbol error frames 0 Late collisions 0 Invalid frames, too large 0 VLAN discard frames 0 Valid frames, too large 0 Excess defer frames 0 Invalid frames, too small 4431 64 byte frames 0 Valid frames, too small 2760 127 byte frames 1161 255 byte frames 0 Too old frames 549 511 byte frames 0 Valid oversize frames 444 1023 byte frames 1591 System FCS error frames 473 1518 byte frames 0 RxPortFifoFull drop frame 0 Too large frames 0 Good (1 coll) frames 0 Good (>1 coll) frames
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Strange Cisco switch ports problem
-I can get a DHCP address
-I can ping to/from a workstation connected to these ports.
-I can ping machines on the internet
-I can telnet from these ports to machines on my LAN.
Here is where it fails:
-I cannot access any windows file shares on other workstations in the domain
-I cannot establish HTTP connections to web sites (no web browsing).
The strange thing is that this is a layer 2 switch, and all my symptoms point to a layer 4 or above problem. But why is the problem specific to these ports?
I've checked the following on the switch:
-all ports are on the same VLAN (1).
-Problem ports 25-28 have no input, output, frame errors, etc. All 0.
-Tried issuing shut and no shut on the ports and it didn't help.
-port counters look normal. Everything looks normal from the switch's perspective.
The only thing I haven't tried is a switch re-boot (it's in production).
Anyone have any ideas or suggestions?
Thanx
Karl