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