Core Switch hang-up

[vlad110226]

Hi folks,

what seems to be the common cause of core switch hang-up?

Could you please advise, what is the best tool to monitor, imminent switch failure? Thanks a lot.

Vlad

[Anand Narayana]

hi vlad,

there could be several reasons for a core switch getting hang-up, if you could tell me your network setp like how it is getting connected, what is edge switch & core switch & what all you have configured on it for giving better solutions.

[ilya.varlashkin]

Do you mean the switch freezes and wouldn't respond even on the console port? In this case software or hardware problems are likely cause, and you should contact TAC (or your support contractor).

If on the other hand you just can't telnet to it from the network or existing telnet session hangs, then it's network stability issue, provided that you can still access switch via console. In this case check routes to the switch, check packet loss on the network and try to localize them down to specific router or link that causes problems. After that fun begings - to find out why that link or router has problems, but it will be easier when problem is localized.

[vlad110226]

hi,

here are the current config of our core switch:

1. 48-port switch is divided by 2, the first 24 ports are config as switch port mode and the next half is via trunk port mode except for the last port which is configured as spanning tree for our Intrusion detection system..

2. connected in the core are servers and level 2 switches or secondary switches. we have a dedicated switch for our routers.

3. we have 7 LAN and 2 wan locations plus international connection (connected via IPVN, E1, leased lines, ISDN

thanks,

Vlad

[ilya.varlashkin]

Vlad, does console respond?

[jackyoung]

Do you mean the last port in core is connecting to SPAN ?

Did you have a syslog server to collect the log from the switch ? You can use it to oberserve the message from switch before hang. However, if it is hardware hang, you may need to find a spare unit to test.

What is the loading of the core switch ?

Hope this helps.

[vlad110226]

here's the port 48 config

Port Mode Encapsulation Status Native vlan

Fa0/48 desirable negotiate not-trunking 1

Port Vlans allowed on trunk

Fa0/48 none

Port Vlans allowed and active in management domain

Fa0/48 none

Port Vlans in spanning tree forwarding state and not pruned

Fa0/48 none

what do you mean by loading of core switch?

regards and ty

vlad

[jackyoung]

What I mean the loading is the CPU and bandwidth loading of the switch. i.e. is it overloaded and cause the problem ?

Did you get any log just before the switch hang ? e.g. open a terminal and connect to the console or setup a syslog server and collect the log from the switch.

[vlad110226]

hi ilya,

i can't ping and telnet to the switch, what i did was powercycled the unit..thanks for your help.

vlad