I plan to replace a Juniper EX4200 that was configured a vlan default gateway, for less downtime, I will setup a new EX4200, copy configuration and transfer network cables from the old switch.
But if the new switch online, it will be two duplicate gateway ip exist on the network, the routing will be failed, how can I fixed this problem? Thanks
Best Answer
To be clear, there are two sub-issues worth identifying--the gateway and the ports. Moving the ports is relatively easy if you connect the two switches together via an ethernet-switching port (I personally use trunks between all switches), copy the remaining port configurations over, then move cables one-at-a-time. This lets you control which ports (and potentially users/services) go down at what time.
The best answer for the gateway is to setup VRRP for that gateway, but it still will require 2 short down times, and has enough configuration gotchas that it may not be worth the time invested. I suggest trunking the two switches together, then simply remove the vlan from one and add it to the other. Using Juniper for both switches, you get the advantage of the commit button. Load your command set on each, the just commit on the first, wait until it completes, then commit on the second. Failback is just as easy: rollback on new, wait, rollback on old.