GLBP & STP

Unanswered Question

Hello!

plz Examine the Attached Topology!

i have 2 Distribution Connected togather Via L2 Link;GLBP Runing as a gateway Load Balency


cONFIGURATION LOOK LIKE THIS:

DS-1

int vlan 10

ip address 1.1.1.2 255.255.255.0

glbp 10 ip 1.1.1.1

glbp 10 priority 120

glbp 10 preempt

!

Ds-2

int vlan 10

ip address 1.1.1.3 255.255.255.0

glbp 10 ip 1.1.1.1

!

I HAVE Aplied this Config for 3 Vlans ..10 20 -30


now I have to Know if i need to configure STP FOR ALL VLAN'S..10-20-30.or its done bu default by STP


IF SO LET ME KNOW THE EXACT STP CONFIG?


10XS



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jorgenolla Sun, 11/25/2007 - 07:21
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After creating the Vlan's there is no need for further configuring STP unless you need to fine tune the timers for faster convergence which is not recommended by Cisco.


Each Vlan will have it's own instance of RSTP.


Remember you must have a GLBP address for each Subnet; meaning one GLBP Group for Vlan 10, one for Vlan 20, and one for Vlan 30.


Best Regards

jorgenolla Sun, 11/25/2007 - 11:32
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This is an option to guarantee which switch will win the election as the Root Bridge by lowering their priority.


It is totally optional, and it should reflect the needs of your network design.


According to your diagram, by setting the root bridge to be different per Vlan, you will load balance your traffic as specified.



Example:


Vlan 10 and 30 - traffic will be forward to DS-1

Vlan 20 - traffic will be forwarded to DS-2


That is if you complete the config as follow:


DS-1

spanning-tree vlan 10 ROOT Primary

spanning-tree vlan 20 ROOT secondary

spanning-tree vlan 30 ROOT Primary


DS-2

spanning-tree vlan 10 ROOT secondary

spanning-tree vlan 20 ROOT Primary

spanning-tree vlan 30 ROOT secondary


Best Regards

Hello

10xs fir ur reply.

without these it work??so what about the election of Root Bridges for Vlans?

DS-1

spanning-tree vlan 10 ROOT Primary

spanning-tree vlan 20 ROOT secondary

spanning-tree vlan 30 ROOT Primary


DS-2

spanning-tree vlan 10 ROOT secondary

spanning-tree vlan 20 ROOT Primary

spanning-tree vlan 30 ROOT secondary


Jon Marshall Mon, 11/26/2007 - 04:21
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Hi Ali


Are there any access-layer switches in this topology ?. If so the above configuration will do a sort of load balancing of your layer traffic ie. vlans 10 & 30 will use DS1 as it active path and vlan 20 will use vlan 20 as it's active path.


It is recommended to set root and secondary switches in your topology rather than leave it to chance.


HTH


Jon

lewwalker Fri, 11/04/2011 - 04:36
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Question regarding this original posting, I have completed the same type of changing implement glbp & stp channging the priority however upon reviewing the various vlan I'm unable to see one of my vlan when running the show command...show spanning-tree root which gives me the indication that I operating without a secondary bridge for that particular vlan.


GLBP working great as it should be the spanning issue concerns me because this is where the majority of my server are located.


thanks


Lewis Walker

Ohio

Kevin Dorrell Mon, 11/26/2007 - 05:05
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The topology will work anyway, even without setting the primary and secondary roots. The position of the layer-2 STP root is independent of the position of the layer-3 active router. If you don't specify which switch is the root, then the protocol will select one according to its own rules, which may not be the optimum result.


However, the routing will be optimised if you adjust the STP and the GLBP/HSRP so that they correspond. That is, it is best that for each VLAN, the active router is the same as the Spanning Tree primary root.


Kevin Dorrell

Luxembourg


Hello Again!

what about this Config according the Diagram:

DS-1

spanning-tree vlan 10 ROOT Primary

spanning-tree vlan 20 ROOT Primary

spanning-tree vlan 30 ROOT Primary


DS-2

spanning-tree vlan 10 ROOT secondary

spanning-tree vlan 20 ROOT secondary

spanning-tree vlan 30 ROOT secondary


is this Config work perfect.?i dont think so because the DS2 Remain Idle..plz do remebere GLBP Acts as a gatewayload balance



any Reply here?10xs a lot

jorgenolla Wed, 11/28/2007 - 12:39
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This configuration will set the Access Layer Switches to forward all their traffic to the distro via DS-1.


All the ports of the access layer switches that are connected to the DS-2 switch, will be in discarding/blocking mode.


According to your diagram GLBP is active from the distro to the Core.


Finally if you want to utilize both links to the distro, you can set the Access Layer Switches to connected to the Distro Layer Switches via L3 links, rather than L2 trunks.


For the above to happen, you must:


1) Have L3 switches on the Access layer.

2) Configure the ports to the distro switches as routed ports.

3) Configure an Internal routing protocol on the Access Layer Switches, so that it includes all the networks configured on the Vlans, and the networks connecting the links to the distro.

4) Configure a Vlan interface as the default gateway for that specific network.


If you have ip cef enabled, as it is the default, after your network converges,ip cef will take care of the load balancing.


If you do not have ip cef enabled, then the routing protocol should take care of the load balancing.


Best Regards




jorgenolla Thu, 11/29/2007 - 08:32
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DS-1

spanning-tree vlan 10 ROOT Primary

spanning-tree vlan 20 ROOT Primary

spanning-tree vlan 30 ROOT Primary

DS-2

spanning-tree vlan 10 ROOT secondary

spanning-tree vlan 20 ROOT secondary

spanning-tree vlan 30 ROOT secondary



This configuration above will not be perfect if you want to load balance between the two distro switches; which is why DS-2 is Idle as you have stated.




BEST CONFIGURATIONS TO LOAD BALANCE FROM ACCESS TO DISTRO VIA LAYER 2.


Vlan 10 and 30 - traffic will be forward to DS-1

Vlan 20 - traffic will be forwarded to DS-2


That is if you complete the config as follow:


DS-1

spanning-tree vlan 10 ROOT Primary

spanning-tree vlan 20 ROOT secondary

spanning-tree vlan 30 ROOT Primary


DS-2

spanning-tree vlan 10 ROOT secondary

spanning-tree vlan 20 ROOT Primary

spanning-tree vlan 30 ROOT secondary



OR


Vlan 20- traffic will be forward to DS-1

Vlan 10 and 30 - traffic will be forwarded to DS-2


That is if you complete the config as follow:


DS-1

spanning-tree vlan 10 ROOT Secondary

spanning-tree vlan 20 ROOT primary

spanning-tree vlan 30 ROOT Secondary


DS-2

spanning-tree vlan 10 ROOT primary

spanning-tree vlan 20 ROOT secondary

spanning-tree vlan 30 ROOT primary



Best Regards.


P.S. (Advises from experts..10xs) I'm a CCNP with 10 years in the networking field.

jorgenolla my Freind,(Advises from experts..10xs)y have got wrong i didnt intend any thing in this.appreciate ur response to me beleive me.OK.now i will take ur suggestion about this:

I Have 65 VLANS.I Will make DS1 root for the even vlan(12) and DS2 for ODD VLAN(11) now what is ur suggestion?

10xs a lot freind



jorgenolla Thu, 11/29/2007 - 11:28
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I Have 65 VLANS.I Will make DS1 root for the even vlan(12) and DS2 for ODD VLAN(11) now what is ur suggestion?


This will work, since you are load balancing as even as possible. Don't over complicated, send traffic from Vlan 1-32 to one distro switch and from 33-65 to the other.


As far as just using DS-1, that is a call for the network engineer that design your network to make.


But remember, you really don't want a single point of failure at any point in your network.


Best Regards

jorgenolla Thu, 11/29/2007 - 12:40
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Yes. It is still recommended that you set the Root Bridge manually, this will prevent the Access Layer Switches from becoming the root bridge.


Best Regards



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