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On 8/22/2012 4:51 PM, Doug McIntyre wrote: > On Wed, Aug 22, 2012 at 02:47:21PM -0500, Justin Krejci wrote: > >> While I agree with the general sentiment that the IP change and switch >> change will likely be smooth, the IP change can be done more >> transparently and has literally nothing to do with the L2 gear. >> To that end, I don't see any reason to not configure/assign the new IP >> block now and let folks start using it right away, even before the >> switch switch. >> > But, we don't have a central router? > > If your border to the exchange right now got a prefix with the next > hop of 206.108.255.3, how'd you get there? You'd have no route to host > for 206.108.255.3. > > That is why I brought up the secondary IPs. Once everybody puts in a > secondary IP in 206.108.255.0/24, they'll know how to try to get to > 206.108.255.3 for my prefix announcement. But I can't really do the > prefix announcement with the next-hop in 206.108.255.3 until everybody > knows how to get to 206.108.255.0/24? > > We can remotely verify that everyone has configured a secondary IP, but that's just the start. You've also got to duplicate ALL of your peer BGP sessions beforehand as well. Why? Well, I don't believe Cisco can initiate a BGP session on a secondary address so once a $C router switches their primary and secondary, they cannot initiate a BGP session. Not a problem yet. What about when the next one does it? Suddenly neither of the Cisco devices can peer with each other.. I've not been through an exchange re-address, but given this limitation, I foresee many problems and the idea of a "flag day" much more appealing - luckily though, most participants are using the route server. Hmm... I assume the BIRD configuration allows you to specify source IP's to be used for each peer? -James CDW ######################################################################## To unsubscribe from the MICE-DISCUSS list, click the following link: http://lists.iphouse.net/cgi-bin/wa?SUBED1=MICE-DISCUSS&A=1