(me) I assume this issue stems from the Cisco ASA firewall's inability to do secondary addresses?
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The problem is more of how VPSes (Xen in this case) work with the Cisco ASA firewall. On a normal box, we can route secondaries through the firewall to the machine without issue; however, with a VPS the secondaries typically like to have a gateway within the same range as their IP. While normally this can be accomidated, our firewall setup tends to be stricter on which IPs can access what (for good reason).
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The firewall solution we provide does allow for rules to be created for secondary IP addresses. It is how Xen handles secondary IP addresses which has caused the this issue, not the hardware firewall itself.
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