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New Member

Spanning tree

Dear ,

I have two question so please answer,might you'll have face this.

 

I have a switch 3750 switch where somebody has executed commands no spanning-tree vlan 2,3,4, when i try to enable by a commnad spanning-tree vlan 2,3,4, and then press enter, then when i do the show run to see the command no spanning-tree vlan 2,3,4 has been removed or not but still it is in the running configuration, it does'nt goes

Another question if suppose i have applied 2 nos of ip helper-address 10.1.1..1 and ip helper-address 10.1.1.2 , is it the request will be send to both or the first from top. If these below commands are working independently then DHCP server should be in sync for their scopes otherwise ther will be a conflict in ip address, anybody can tell me windows DHCP server scopes are working in sync.

int vlan 1

ip add 10.1.1.254 255.255.255.0

ip helper-address 10.1.1.1

ip helper-addres 10.1.1.2

 

thanks pleas reply

 

1 ACCEPTED SOLUTION

Accepted Solutions
Silver

HiFrom tho top of my head, I

Hi

From tho top of my head, I think it is 128 instances.

So, for the first 128 vlan that is created there will be one instance created to each. All other vlans will not participate in the spanning-tree calculation. They will, however, forward the bpdu:s so other switches have the opportunity to react and take actions.

3 things to consider here

1.Remove all vlans that is not needed in the switch.

2. If, after point one, there is still more than 128 vlans, then You must decide wich of them to run spanning-tree on.

3 Go for mst instead

/Mikael

8 REPLIES

HelloSounds like stp was

Hello


Sounds like stp was turned of for those vlans, which personally I would NOT do, you should never disable STP if you are running it in you network.

sh spanning-tree summary ( this will show you what vlans are running spanning tree
sh int trunks - this will show what vlan are allowed across you trunk interfaces.

 

DHCP
Your windows dhcp servers should have the same scopes on either server- however its best practice to separate the scopes ip addressing between each server 

So say a subnet  of 24 bit address can run on either server when both working at the same to time they allocate only half of  this 24 bit addressing from either server, and if the either one of the servers goes down then the active server can manually activate is other part of the scope to take the responsibility

In the dhcp server manager you  can R/C on a scope and chose replicate ( manual ) or in the dhcp server option choose to synchronise automatically and you can check is this sync has been performed by checking the dhcp serial number - I think you R/C on the server name and this serial number should be increase at each synchronisation on either server.

res

Paul

 

 

 

Please don't forget to rate any posts that have been helpful. Thanks.
Hall of Fame Super Silver

There is one aspect of the

There is one aspect of the question from the original poster that Paul has not addressed. If there are two helper addresses configured on an interface then a copy of the request will be forwarded to each of the servers. It is not sent to just the first one but is sent to both.

 

HTH

 

Rick

New Member

That is correct. For instance

That is correct. For instance we have two IP helpers, one is for DHCP and one is SCCM PXE server. So traffic is sent to both in the event we need to image a PC.

New Member

Dears why those spanning tree

Dears

 

why those spanning tree are not enabling after applying the cammand also.

As Richard told that the request will go on both server so they both have to be in syn and active active  so i dont thing windows DHCP server has sync feature,

 

Actually i am appying these redundant DHCP for my ip phones, Is it anybody of you tell me that Cisco Callmaanger DHCP servers are sych to each other for DHCP scopes.

 

Thanks

Silver

Hi Regarding the spanning

Hi

 

Regarding the spanning-tree question. There is a limit to 128 spanning-tree instances that the switch support. By defualt one instance is started automaticly when a vlan is created. So if this is Your problem, You have to remove some vlan or disable spanning-tree for a couple of the others first.

/Mikael

New Member

Dear For 3750 switch there

Dear

 

For 3750 switch there are how many instances??? yes i have seen the switch configuration there are too many 300 vlans in the switch.

Thanks

Silver

HiFrom tho top of my head, I

Hi

From tho top of my head, I think it is 128 instances.

So, for the first 128 vlan that is created there will be one instance created to each. All other vlans will not participate in the spanning-tree calculation. They will, however, forward the bpdu:s so other switches have the opportunity to react and take actions.

3 things to consider here

1.Remove all vlans that is not needed in the switch.

2. If, after point one, there is still more than 128 vlans, then You must decide wich of them to run spanning-tree on.

3 Go for mst instead

/Mikael

New Member

Thanks for confirming,that

Thanks for confirming,

that cisco 3750 switch can support only 128 vlan instaces only. and for suggesting MST.

Thanks

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