Implementing GLBP protocol between two 2851 Routers

Esfandiarfard_2 · ‎12-18-2013

Hello,

Please advise when you get a chance. We have two older 2851 Routers that primarily function as sending traffic for different VLANS thru different firewalls but a single point of failure at this point ( Only one router is connected and active now). I was exploring into the idea of connecting the second router and use GLBP. I have included the configuration of show running-config as well as what I plan to add to both routers. Does that help me in having a redundant router. Thank you.

On 2851 Router currently connected to our Gig switch

•1) Configure terminal
•2) Interface G0/0 (Ip address 172.15.9.x subnet)
•3) GLBP 1 IP 172.15.9.X
•4) GLBP 1 PRIORITY 110
•5) GLBP 1 NAME MAIN ROUTER

On Second 2851 Router which I am planning to connect

•1) Configure terminal
•2) Interface G0/0 (ip address 172.15.9.x subnet)
•3) GLBP 1 IP 172.15.9.X
•4) GLBP 1 NAME MAIN ROUTER

Jon Marshall · ‎12-18-2013

GLBP would allow you to load balance the hosts in the 172.15.9.x subnet between both routers. See this link for basic config for GLBP -

https://supportforums.cisco.com/docs/DOC-4549

Couple of things to note.

1) You are currently bridging between gi0/0 and gi0/1 on your router. Are you planning on removing that config and only using gi0/0 ie. assign the actual IP to gi0/0 ?

2) If you do don't forget to move the route map from the BVI interface to the gi0/0 interface on the existing router.

Jon

Esfandiarfard_2 · ‎12-18-2013

Jon,

Thank you very much. I will make sure step 1 and 2 that you pointed out are implemented. g0/0 will point to the IP of BV1 and remove BV1 all together as well as route-map will go under the g0/0 interface. I did read the link and very helpful information. The last piece of information I like to confirm is it says all hosts must point to virtual IP as the default-gateway. We have a 3750 stack that defines 14 active VLANS and does the routing for all VLANS. All hosts in VLAN1 currently point to 3750 IP as their gateway. I have static router on 3750 that says send everything to 2851. Do I just need to replace that with Virtual IP.

For reference # 3750 has 172.15.9.191, 2851 Router has 172.15.9.230

172.15.9.0 is directly connected, Vlan1

172.29.0.0/24 is subnetted, 13 subnets

172.29.51.0 is directly connected, Vlan51

172.29.50.0 is directly connected, Vlan50

172.29.3.0 is directly connected, Vlan3

172.29.2.0 is directly connected, Vlan2

172.29.5.0 is directly connected, Vlan5

172.29.4.0 is directly connected, Vlan4

172.29.7.0 is directly connected, Vlan7

172.29.6.0 is directly connected, Vlan6

172.29.9.0 is directly connected, Vlan9

172.29.8.0 is directly connected, Vlan8

172.29.11.0 is directly connected, Vlan11

172.29.10.0 is directly connected, Vlan10

172.29.12.0 is directly connected, Vlan12

192.168.4.0/24 [1/0] via 172.15.9.230

209.101.218.0/30 is subnetted, 1 subnets

209.101.218.176 [1/0] via 172.15.9.230

216.132.246.0/30 is subnetted, 1 subnets

216.132.246.128 [1/0] via 172.15.9.230

192.168.0.0/24 [1/0] via 172.15.9.230

192.168.2.0/24 [1/0] via 172.15.9.230

192.168.3.0/24 [1/0] via 172.15.9.230

* 0.0.0.0/0 [1/0] via 172.15.9.230

Jon Marshall · ‎12-19-2013

I thought you only had one LAN subnet and were going to use GLBP for that subnet on the routers. But if you are routing vlans off the 3750s then GLBP is probably not the solution.

Do you want to use both routers equally or do you want to use one router and have the other only as backup ?

Jon

Esfandiarfard_2 · ‎12-19-2013

Jon,

I was thinking active/active (GLBP). Remember the 2851 is really just doing the decision making of VLAN1 going out of one firewall and ISP ( Time Warner for example)and VLAN2 and VLAN 3 going out of another firewall ( Megapath) per the acces-list and route-map. I wanted to eliminte a single failure of a 2851 taking us down. I wanted to put second 2851 just to be there as the alternate meaning that if original router has a power supply failure /memory failure then we are not down since we are 24X7 operation. Any thought is much apperiaciated.

Jon Marshall · ‎12-19-2013

GLBP works by allocating different routers to act as the gateway for different clients. But your clients are all sitting behind the 3750. The only client your routers will see is the 3750 so it can't load balance as it is only one client.

If you only want one router active for all traffic and the other standby you would be better to use HSRP and make the primary router the HSRP active gateway and then use HSRP tracking to keep track of the WAN interface.

If you wanted to use both routers you would be better of using L3 routed links to the routers and doing equal cost load balancing.

Unless i am missing something about your topology i am struggling to see what benefit GLBP gives you.

Jon

Esfandiarfard_2 · ‎12-19-2013

Jon,

Thank you. HSRP makes much more sense . Active/standby makes much more sense. Thank you for all the good information.