Redundancy Project: How do I setup up GLBP and STP?

Answered Question
Sep 26th, 2014
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I very new to this but eager to learn. This is a project I am currently working on. How do I setup up GLBP and STP? I have two Cisco 2800 routers with two fast ethernet ports each, one Switch 3500, and two Switch 2950. I want to connect the two routers to my home Apple router for internet access. Then I will connect both routers to the 3500 switch and connect the other two switches to it as well. From there I will add a server to provide dhcp and dns but that is later. My question is how do I start? I've seen the configurations for glbp for the routers and setting up stp for the switches but I just can't seem to put it together.

Correct Answer by Walter Astori about 2 years 10 months ago

Switch 3500 connect to Switch 2950 with two cable
Switch 3500 connect to Switch 2950 with two cable
Switch 2950 connect to Switch 2950 with two cable

One router 2800 connect to Switch 2950 with one cable
One router 2800 connect to Switch 2950 with one cable

On the switch 2950 (1) you can configure the PVST :
spanning-tree vlan 1,2 root primary

On the switch 2950 (2) you can configure the PVST :
 spanning-tree vlan 1,2 root secondary

On the Cisco 2800 (1) you can configure :
 
interface FastEthernet 0/0
 ip address 10.1.1.1 255.255.255.0
 glbp 10 timers 5 18
 glbp 10 priority 254

On the Cisco 2800 (2) you can configure :
 
interface FastEthernet 0/0
 ip address 10.1.1.2 255.255.255.0
 glbp 10 timers 5 18

 

 

 

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InayathUlla Sharieff Fri, 09/26/2014 - 22:49
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  • Cisco Employee,

STP and GLBP are two distant protocols and they dont work together they work independly.

STP is use to prevent layer 2 loops.

GLBP is used for redundancy or load balancing protocol.

 

Based on your topo:

Run the GLBP on routers and STP on the switches.

HTH

 

Carlos Trevino Sun, 09/28/2014 - 16:30
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Thank you for your reply and yes I understand they are two different protocols. I guess I should have been more specific with my question. The problem I have at the moment is how do I connect two routers to one switch? Is it as easy as just setting up GLBP on the routers and STP on the switch and then just plugging in both routers? Do I have to do any configuration so that the switch knows there is two routers being used? Could you help me out with the commands I need?

Correct Answer
Walter Astori Mon, 09/29/2014 - 02:12
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Switch 3500 connect to Switch 2950 with two cable
Switch 3500 connect to Switch 2950 with two cable
Switch 2950 connect to Switch 2950 with two cable

One router 2800 connect to Switch 2950 with one cable
One router 2800 connect to Switch 2950 with one cable

On the switch 2950 (1) you can configure the PVST :
spanning-tree vlan 1,2 root primary

On the switch 2950 (2) you can configure the PVST :
 spanning-tree vlan 1,2 root secondary

On the Cisco 2800 (1) you can configure :
 
interface FastEthernet 0/0
 ip address 10.1.1.1 255.255.255.0
 glbp 10 timers 5 18
 glbp 10 priority 254

On the Cisco 2800 (2) you can configure :
 
interface FastEthernet 0/0
 ip address 10.1.1.2 255.255.255.0
 glbp 10 timers 5 18

 

 

 

Carlos Trevino Mon, 09/29/2014 - 14:21
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Ok so I set it up as you said. Everything seems to be working except the interface from the root switch to the router is down. It is "no shut" and the cable is good so not sure whats going on. Only on router is allowing traffic. Any idea why?

Walter Astori Tue, 09/30/2014 - 01:51
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Can you execute the following command :

show spanning-tree interface (the interface where the router is connect)

Carlos Trevino Tue, 09/30/2014 - 07:12
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It worked. I believe what was happening for whatever reason Router 2 was turning on faster and becoming the active router. When I turned on Router 1 first waited a bit then Router 2 and waited a bit it started working. Thank you.

Carlos Trevino Tue, 09/30/2014 - 07:15
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I have another question for you since.  Now that I have glbp on both routers and a virtual router in-between how do I set up NAT. I have set up nat before but I have read NAT needs to return back to the same router and glbp may cause a complication. I read instead of round robin I could use host dependent but not sure how I would do this. I am not looking for anything fancy I am ok with permit all for now.

Carlos Trevino Tue, 09/30/2014 - 08:42
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Never mind I figured it out. Wasn't too difficult didn't even use host dependent stayed with round robin. All I did was set the default gateway to the virtual router and everything seems to be working correctly now. Thank you for all your help.

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