Open Stack

Hey, all.   I've got a setup akin to this:

[Ext. host] <--> [Floating IP] <--> [qrouter] <--> VM

Note that all of this worked prior to a hurricane-induced system outage.

If I boot the VM, I can ping it from outside... briefly.  Once the 
qrouter's ARP table cache entry expires, however, it doesn't refresh.   
However, if I initiate a ping *from* the VM -- even just to the router 
-- the router's ARP cache re-populates and everything works great.

Observations:
* When the ARP entry is expired and I ping from the outside, the qrouter 
sends out ARP requests that are never seen by the VM:
21:22:47.597303 IP 172.23.9.40 > 192.168.76.13: ICMP echo request, id 
14074, seq 1, length 64
21:22:52.606160 ARP, Request who-has 192.168.76.13 tell 192.168.76.1, 
length 28
21:22:53.606161 ARP, Request who-has 192.168.76.13 tell 192.168.76.1, 
length 28
21:22:54.606183 ARP, Request who-has 192.168.76.13 tell 192.168.76.1, 
length 28
...
whole lotta nothin' goes here.  Not bothering to show the VM, because 
there's literally nothing to show.


* When the ARP entry is expired, and I ping from the VM, here's the 
sequence (sniffing from the qrouter):
21:39:58.344340 IP 192.168.76.13 > 192.168.76.1: ICMP echo request, id 
1401, seq 1, length 64
21:39:58.344403 ARP, Request who-has 192.168.76.13 tell 192.168.76.1, 
length 28
21:39:58.988908 IP 192.168.76.13.35066 > 8.8.8.8.domain: 933+ PTR? 
1.76.168.192.in-addr.arpa. (43)
21:39:59.342164 ARP, Request who-has 192.168.76.13 tell 192.168.76.1, 
length 28
21:40:00.342159 ARP, Request who-has 192.168.76.13 tell 192.168.76.1, 
length 28
21:40:03.357296 ARP, Request who-has 192.168.76.1 tell 192.168.76.13, 
length 28
21:40:03.357361 ARP, Reply 192.168.76.1 is-at fa:16:3e:30:97:50 (oui 
Unknown), length 28
...
and everything works great.

----------------------------------------------------

Any idea on what's going on here?

Thanks much!

-Ken