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I run:

/sbin/ifconfig eth0:10 netmask down

on box1, and on box2:

/sbin/ifconfig eth0:10 netmask up

Both boxes are located on the same network.

After migrating, I'm able to ping the ip from both servers, I notice it responds 10x faster on box2 than on box1 so it seems like that went ok. However I'm not able to ping the ip from outside of the network.

eth0 on both boxes are the public ips, the alias is also a public ip.

When I move the ip back to box1, I'm able to ping it outside of the network without any issue.

I am also able to ping the public ip (eth0) on box2 just fine, so it doesn't appear to be a firewall issue.

Do the routers need time to update the new one to point to the new MAC address?

What am I missing?

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Does the problem disappear if you ping the router with the alias address as source address? – Hauke Laging Feb 14 '13 at 18:20
up vote 1 down vote accepted

You need to send gratuitous arp. Packages like heartbeat and keepalived will do this for you. Otherwise, look at arping.

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Thank you so much! Running: arping -U -I eth0 Made the box respond to that ip immediately. – Kevin Korb Feb 15 '13 at 0:46

Kevin instead of using ifconfig to set the virtual interface down, use ip to remove it:

ip addr del dev eth0

and yes, the router may need some time to update it's arp table. But, if you have access to it, you may manually remove the arp entry from the table, although the time for it to update isn't that long.

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Thanks, unfortunately I do not have access to the upstream router at all. But you did hit the nail on the head knowing it was an ARP table issue. – Kevin Korb Feb 15 '13 at 0:49
Not having access to your upstream router makes it just a matter of time, and it isn't that long. ;-) – fboaventura Feb 15 '13 at 18:46

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