Cisco 2924 and Spanning Tree

[azzurri]

My Intallation:
VWinNT4.0,SP5 and Switched Network (cisco 2924)

My Problem:
Some PCs shows the event ID 1005 that means a timeout by getting the IP Address from the DHCP Server. The user do not see anything.
Microsoft Doc Q168455 is talking about problems with spanning tree.
Has someone experience with this problem ???
Thanks
Nello [sig][/sig]

 

[Shaner]

The problem is in your router config. Under the interface inter the ip helper-address <dhcp server address> command. This should do it.

Shane [sig][/sig]

 

[jroysdon]

I believe he's on the same LAN. The problem is that STP is putting the ports on the 2924 in blocking mode when the PC's first power up, and given that they probably power up very fast, the port doesn't go into forwarding mode when the DHCP request tries to go out, and thus the problem. Two solutions are to shorten the STP port blocking to fowarding delay, or remove it completely (just don't patch your switches in a loop, or don't set this last config on any ports that will not be directly connected to an end node). This first line will configure your switch to only wait 15 seconds before going from blocking to forwarding mode (should be adequate for STP to work, but PCs to boot and have DHCP or whatever else work):
spanning-tree vlan 1 forward-time 15

Worst case, just nuke the delay altogether (I've done this for some ultra-fast booting PCs that boot in DOS first, check the network for config changes, then continue booting normally). What this will do is disable the default wait time between blocking and forwarding on the ports when they first come up:

interface FastEthernet0/1
spanning-tree portfast
!
interface FastEthernet0/2
spanning-tree portfast
!
interface FastEthernet0/3
spanning-tree portfast
!
interface FastEthernet0/4
spanning-tree portfast
!
interface FastEthernet0/5
spanning-tree portfast
!
interface FastEthernet0/6
spanning-tree portfast
!
interface FastEthernet0/7
spanning-tree portfast
!
interface FastEthernet0/8
spanning-tree portfast
!
interface FastEthernet0/9
spanning-tree portfast
!
interface FastEthernet0/10
spanning-tree portfast
!
interface FastEthernet0/11
spanning-tree portfast
!
interface FastEthernet0/12
spanning-tree portfast
!
interface FastEthernet0/13
spanning-tree portfast
!
interface FastEthernet0/14
spanning-tree portfast
!
interface FastEthernet0/15
spanning-tree portfast
!
interface FastEthernet0/16
spanning-tree portfast
!
interface FastEthernet0/17
spanning-tree portfast
!
interface FastEthernet0/18
spanning-tree portfast
!
interface FastEthernet0/19
spanning-tree portfast
!
interface FastEthernet0/20
spanning-tree portfast
!
interface FastEthernet0/21
spanning-tree portfast
!
interface FastEthernet0/22
spanning-tree portfast
!
interface FastEthernet0/23
spanning-tree portfast
!
interface FastEthernet0/24
spanning-tree portfast
[sig][/sig]

 

[Farmer]

I agree with jroysdon. I think you need to turn spantree portfast on (or at least shorten the STP blocking time). QUESTION: Do the PC's work after you warm boot or does this only happen on a cold boot?

Most NICs will not drop their link status on a warm boot and thus prevent the switch from reinitializing spanning tree. Chances are if it work after a warm boot but not after a cold boot, your problem lies in turing off or tweaking portfast.

Also, if you are not using trunking or channeling, turn them off as well. They take cycles from the processor (turn off CDP on you server ports too!)

John [sig]<p>John Kowalski<br><a href=mailto:john.kowalski@eds.com>john.kowalski@eds.com</a><br>[/sig]