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From Sanjeev Neelarapu <>
Subject RE: SSVM Public IP, NAT and L2/L3 connectivity
Date Fri, 18 Oct 2013 11:58:48 GMT
Hi Adrian,

Please find responses inline

-----Original Message-----
From: Adrian Lewis [] 
Sent: Friday, October 18, 2013 4:41 PM
Subject: SSVM Public IP, NAT and L2/L3 connectivity

Hi All,

Still in the planning stages of deploying my first CS install and I have a question about
the SSVM and the apparent requirement for a public routable IP address. From what I can gather,
the only interaction that the SSVM has with the internet is for downloading files from user
or admin supplied URLs. Does this mean that nothing actually makes inbound connections directly
to it from the internet and that it only ever makes outbound connections? If so, why does
it need a public IP?

[Sanjeev]: I could think of one scenario which is copying templates from one zone to another
zone where zones are at different geographical locations(i.e. two zones are connected using

Would it be possible to simply have a route to the internet via the management network or
to give it an IP from private network pool that has access to the internet via some other
NAT device?

[Sanjeev] As per the cloudstack terminology public ip does not mean that they are real public
IPs. They can be private IPs from which internet can be accessed using other NAT device.

Secondly, I've seen some excellent slides from Geoff Higginbottom but I'm still not quite
sure whether the SSVM actually has four vNICs or whether it simply needs access to four networks
via a lesser number of vNICs. Can anyone clarify how many vNICs each SSVM has and what the
routing table looks like on the VM itself, especially where the management server and secondary
storage server are on subnets accessible via a L3 hop and not directly attached to either
the hypervisor mgmt or SSVM vNICs (and these subnets aren't accessible by a default route
on the SSVM)?

[Sanjeev] It is necessary that there should be four vNICs on SSVM , each belonging to only
one network. 
Management and Storage servers need not be on the same subnet. They should be accessible via
a L3 hop.

My main concern is the public IP requirement as I'm finding it very difficult to get enough
public IPs from my DC, especially where there doesn't appear to be a reason for it. I can't
simply get a nice big block of IPv4 like some other CS users may be used to! I'm considering
joining RIPE but this is not especially cheap and doesn't seem to guarantee that I'd get an
assignment of IPv4 addresses anyway.




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