I know there are many assumptions to this question but: Would it be possible to simultaneously configure all area x routers through something like SNMP for the purpose of merging with another area? If this is possible, could someone absorb a multi-area campus network into one area within a few minutes?
1 Answer
The problem is being able to configure routers while you're in transition.
Consider a network with two areas ( 0 and 1). If you change the configuration of the ABR, then all the routers in area 1 will drop their neighbor relationship, and you won't be able to reach them to change their configurations.
It might be possible if you choose the configuration order very carefully, so that you configure the most distant routers first and work your way back. But it's risky, and if you make a mistake, you will have to reconfigure the routers from the local console.
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Where you start to peel back is important, and mistakes require local-fixes. Got it. From the outset, you would need to identify a central area, and work you way towards it. What area properties would help inform your decision on the ideal central area?– GedCommented Mar 17, 2022 at 16:45
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I'm not sure you can generalize like that. You have to be sure that changing one router doesn't disconnect you from any unchanged routers. Commented Mar 17, 2022 at 16:47
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"Stepping stones". If you change the OSPF config on the ABR, the ABR is still physically in the same network, so you'd still be able to get to the now-cut-off routers. You might not be able to telnet directly from your desktop, but you'll be able to telnet to something that can. It makes the job a Right Mess(tm) if you get the order wrong. I've done this with IGRP to EIGRP (a much simpler process); if you miss a device or get out of order, then there's going to be a string of connections to get back in there. (vty acl's must allow this!)– RickyCommented Mar 17, 2022 at 17:03
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