Connection drops after replacing 3Com hub w/ Cisco 2950 1

[markgramlich]

Background:
This is a small non-profit. We have been slowly replacing our old 3Com dual speed 10/100 hubs (3C16611) with Cisco 2950 10/100 switches (WS-C2950-12). Most of these have been pretty uneventful. However, one building has had a lot of problems. With the old 3Com hub, the users would get connected in the morning and stay connected all day long. No connection drops during the day. However, when the Cisco 2950 got swapped in, the connection drops started. The drops seem to happen at almost any time of the day or night. It would take a minute or more for the connection to come back up. The drops cause MS Outlook problems and problems with an in house MS Access application. I checked and tested the cables. I moved the users to different ports on the switch. I configured the users systems 10/100/1000 interface from auto negotiate to 100FD and 100HD. Nothing seemed to help. When I put the 3Com hub back in the connection drops went away. I'm at a loss and open for suggestions.

 

[ISPKing]

Try another 2950 Switch. The 2950 are old, and bottom of the bucket switches, but they do a great job for small environments.

CCNP

 

[burtsbees]

ISP---come on, dude...lol

"It would take a minute or more for the connection to come back up."

What does this indicate? Replacing the switch will just duplicate the problem...

Mark---first off, please post a config. Second, are they hubs that you are replacing with switches, or are the 3com's actually switches? This really sounds like a spanning-tree problem, as a reconvergence from blocking to forwarding is almost a minute (50 seconds)...

/

tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!

 

[burtsbees]

However, ISP, you could be right. I'll buy you a tall boy if you are...

/

tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!

 

[markgramlich]

We have a small environment in some ways. Our largest building has 14 users. Our smallest buildings have 2 users. We have 7 buildings total.

The 3Com equipment we are replacing is a 3C16611 10/100 hub, not a switch.

Here is the sho conf from the Cisco 2950.




Using 981 out of 32768 bytes
!
version 12.0
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Cisco_Switch_Milestone
!
enable secret 5 ********
!
!
!
!
!
!
ip subnet-zero
!
!
!
interface FastEthernet0/1
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface VLAN1
ip address 192.168.0.231 255.255.255.0
no ip directed-broadcast
no ip route-cache
!
ip default-gateway 192.168.0.15
snmp-server engineID local 0000000902000005DCCB8EC0
snmp-server community private RW
snmp-server community public RO
!
line con 0
exec-timeout 0 0
transport input none
stopbits 1
line vty 0 4
password ********
login
line vty 5 15
password ********
login
!
end

 

[PeterHurst]

It's possible the wiring in the building is causing an issue. ISP Could be right about the switch. None too sure on 2960's but usually if the ASICs are faulty it'll affect a group of ports together - often in groups of four or eight.

Try looking at the logs for the switch - do the ports actually log errors? Trace ports and swap them over so - does the problem stay with the wire oor the port?

Reset port counters and then check them regularly for errors, dropouts and if Half Duplex collisions. That also reminds me - check that the ports have come up the same on the PC as the switch - eg if auto at both ends should come up 100 full generally.

 

[burtsbees]

Take that switch and swap it with another in another building. If the problem follows the switch, then obviously the switch is faulty. This is the next logical step.

/

tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!

 

[MrOyvind]

Hi

Also try to turn on logging so see the events.
switch(Config)#logging on
switch#sh log.
Use sh post too see the "power on self test" switch hardware health status.


Oyvind

 

[ISPKing]

lol? loggin on?

logging buffered*

CCNP

 

[burtsbees]

logging buffered 64000
logging trap debug
logging hyena pee
logging yo mammy
logging Green Eggs and Ham

The first two are actual commands.

/

tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!

 

[Cluebird]

On all the ports connected to the workstations add the following:
Switch(config-if)#switchport mode access
Switch(config-if)#spanning-tree portfast
Switch(config-if)#switchport nonegotiate
Switch(config-if)#spanning-tree bpduguard enable

Post your topology, but I suspect you have spanning-tree issues.

HTH

 

[ISPKing]

OR just type switchport host.

Does all the above mentioned. Except bpdu gaurd.

CCNP

 

[Cluebird]

Or just run the cisco-desktop macro and you'll get port-security, too.

 

[ISPKing]

touche'

CCNP

 

[markgramlich]

Finally got back to this. I borrowed an ethernet cable tester. The one on site only tested 10mbps. The borrowed tester found two cable problems. First - was an APC P10BT surge arrestor that had problems. Second - was a patch cable that did not have pin 1. I removed the APC P10BT and replaced the patch cable.

Now I would like to remove the hub and put the Cisco switch back in service.

I'm now trying to understand 'spanning tree' and the implications.

We have a small campus environment. Each building has a hub for connections to devices within the building. We have 100mbps multimode fiber between the buildings. We have 'Transition Networks' media converters in place to convert the copper ethernet to/from fiber. All the fiber connections terminate in one building. We have a Cisco 2540 switch as our central switch. Each build hub has only one connection back the the central switch. Physically and logically, the network is a star.

Would there be a concern using "switchport host" in this environment?

 

[imbadatthis]

if:

- there are no loops (physical)
- you are not using vlans (doesn't sound like it)

then you dont really have to worry about spanning-tree.

im guessing that is the case, since you have been using hubs until now.

as far as the switchport host command goes, just to be safe for the future (maybe you add vlans, or loops, or something later) make sure you only add that to ports that are connected to PC such as workstation, server, or printers




We must go always forward, not backward
always up, not down and always twirling twirling towards infinity.

 

[burtsbees]

switch(config)#int range fa0/1 - 16
switch(config-if-range)#switchport host

for example, how to configure interfaces fa0/1 thru fa0/16 all at the same time with the same commands.

ISP---switchport host simply puts all ports into access mode and portfast---no nonegotiate either (of course I have never had to do that once I put the switchport into access mode).

Tad---the cisco-desktop macro does switchport security, but it locks the port to only one MAC---that's a little hassle...

Also, to see the commands under each macro available, you do the

switch#sh parser macro

To do the macro, you would do (on a range):

switch(config)#int range fa0/1 - 19
switch(config-if-range)#macro apply cisco-desktop

or whatever macro you want to use.

/

tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!

 

[Cluebird]

Hint...if you don't like the built in macros, write your own.

 

[burtsbees]

Actually, I have. I have also screwed with the HTML pages for SDM and made my own thing. 'Tis all goodness, now. Thank you for your concern for my mental and emotional well-being, Tad. You'll never know what that means to me...thank you, thank you, thank you! Did I ever tell you that you're my hero?

/

tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!

 

[ISPKing]

Afaik there is no 2540 switch. I am curious as to which number you confused that with.

CCNP