If your production router has an unused Ethernet interface, then you would be in a good position for testing GLBP on it with minimal possible impact to your production network. Otherwise, you might be able to define a GLBP address on an active production interface. (The reason I say might, I'm not 100% certain what impact the existing secondary addresses might have. There shouldn't be any issue with a GLBP address and "normal" ip address sharing the interface.)
What you do want to avoid, for a test, is using one of your existing production gateway addresses. I.e. it's fine to share a "new" virtual address between two routers (assuming it doesn't conflict with any other device), but if you reassign an existing gateway address, you can easily impact active users.
Collin's post, to avoid tests on production systems, is good advice, but if your really suffer from lack of equipment, it might be doable. If you do end up testing on production equipment, next best situation (rather than having dedicated test equipment) is to attempt to limit your changes/tests to non-peak times.
Just tried this on a 2801:
Router#sh run in fa 0/1
Current configuration : 203 bytes
ip address 10.1.2.1 255.255.255.0 secondary
ip address 10.1.3.1 255.255.255.0 secondary
ip address 10.1.1.1 255.255.255.0
glbp 1 ip 10.1.1.2
So, it appears you might be able to test GLBP on a production interface.
Certainly, testing on production router is not my first choice and so i wanted to confirm if it would effect any of the current users.
I have 2 interfaces, but both are used.
I will be using, one of the interface and give it a new virtual ip as gateway with the spare router.
I wanted to further confirm that, if the interface already have a primary IP and 2 secondary IPs in use, and i create a virutal IP for glbp, the users would still be able to use the primary and 2 seconday IPs on the router ? I mean sort of, glbp virutal ip would not take precendence as the default ip for all routes etc...
As long as your other hosts are using an existing explicit gateway address, the GLBP test address, I believe, should not be an issue. For testing, you'll have to set those hosts that want to use the GLBP virtual address as their gateway's address. If, on the other hand, you get to the gateway address using proxy, I suspect, but I'am uncertain, the router might return the GLBP address. (Reason I'm uncertain about proxy gateway, when using HSRP/GLBP/VRRP have always used explict host gateway addresses.)
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.