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On Aug 23, 2012, at 11:33 , James Stahr <[log in to unmask]> wrote: > 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. It can, actually... You just need to add update-sourceto the configuration. > > Hmm... I assume the BIRD configuration allows you to specify source IP's to be used for each peer? > I don't know of any router configurations that don't. Owen ######################################################################## To unsubscribe from the MICE-DISCUSS list, click the following link: http://lists.iphouse.net/cgi-bin/wa?SUBED1=MICE-DISCUSS&A=1