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From Chiradeep Vittal <>
Subject Re: Network architecture question
Date Wed, 10 Apr 2013 19:01:58 GMT
Please take a look at

Slides 32-39 explain the networking layout in security groups in basic
The VR (one per pod) simply dispenses DHCP and user data. It is not a
The firewall is implemented at the hypervisor level. This is what allows
it to scale

On 4/10/13 7:01 AM, "Murali Reddy" <> wrote:

>As Chiradeep mentioned, 'basic zone' is solution you should be trying out.
>With basic zone, you could associate guest subnet per pod, there is no
>VLAN's required in the zone. Your L2 broadcast domain is restricted to
>POD. POD becomes unit of scale in basic zone, so east-west traffic across
>the rack/POD's is through the router that connects TOR switches of POD.
>Please try basic zone deployment and let us know if you still see
>On 10/04/13 7:13 PM, "Justin Grudzien" <> wrote:
>>I looked at Security groups and I am not sure how this solves my
>>problems. Sure it provides guest isolation but that is through the
>>virtual router correct? The underlying physical network --outside of
>>cloudstack-- is still layer 2? That is what I am concerned with. When
>>defining what IPs my guests sit on CloudStack assumes that those are
>>available, or tagged, on every host in my zone. If I have every host
>>tagged with the guest network then broadcast packets, like ARP, will hit
>>every box, regardless of whether a VM runs on it at all. My network
>>engineers are worried that any kind of broadcast storm, or spanning tree
>>loop, could take the whole cloud down. Does this make sense or am I still
>>missing something?
>>What we are looking at is creating a zone per physical rack of servers
>>implementing the shared network offering. This allows my underlying
>>network to be layer 3 between cabinets and limits my layer 2 guest
>>traffic to far less servers. Between cabinets I will use routing for VMs
>>to talk to each other. The problems this introduces is that CloudStack
>>doesn't let me mount the same secondary storage for images so I have to
>>replicate that data. It would be nice to be able to mount the images
>>across all zones but leave the snapshots local to the zone.
>>We have been intensively building and rebuilding CloudStack for the last
>>three weeks and nowhere have I seen the ability to pin a guest subnet to
>>a rack (pod) of servers. This is what suggests that the guest networks
>>must be tagged on all physical host ports and why I am concerned about
>>the large layer 2 domain.
>>Sorry this was long winded some of these concepts are difficult I convey
>>over email.
>>Sent from my iPhone
>>On Apr 9, 2013, at 12:26 PM, Chiradeep Vittal
>><> wrote:
>>> You can do bonded nics in basic zone. The limitation with basic zone is
>>> that the Vms cannot have multiple nics. Did you need multiple nics for
>>> your vms?
>>> If you need advanced network services such as static NAT and load
>>> balancing, advanced networking is probably your best bet (currently,
>>> unless you want to invest in a Netscaler for these services).
>>> Not sure that VXLAN will solve your problems since that has scaling
>>> problems as well. On vSphere an NX1000v DVS can only handle about 64
>>> hypervisors IIRC.
>>> On 4/9/13 5:39 AM, "Justin Grudzien" <> wrote:
>>>> We have 2 pairs of bonded 10g nics on each box. Wouldn't that require
>>>> advanced network? Is it possible to do the security groups with small
>>>> networks in advanced networking?
>>>> Justin 
>>>> Sent from my iPhone
>>>> On Apr 9, 2013, at 12:38 AM, Chiradeep Vittal
>>>> <> wrote:
>>>>> Have you considered using a basic zone?
>>>>> With security groups you can have *lots* (thousands of) with very
>>>>> L2
>>>>> networks.
>>>>> On 4/8/13 10:28 PM, "Justin Grudzien" <> wrote:
>>>>>> My team has been working for three weeks with CloudStack
>>>>>> design and we are struggling to put together a network architecture
>>>>>> that
>>>>>> we feel will scale. From everything I can tell, CloudStack requires
>>>>>>a a
>>>>>> very large layer 2 network when using shared guest networks. We are
>>>>>> looking to deploy almost a thousand physical hosts across 25
>>>>>> with over 4000 VMs in the next 18 months and having a broadcast
>>>>>> this large feels problematic.
>>>>>> How have others solved this problem? I don't have a need or a desire
>>>>>> for
>>>>>> isolation and even if I had 100 guest networks I would still have
>>>>>> tag
>>>>>> their VLANs into every host port. There doesn't seem to be a way
>>>>>> tie a
>>>>>> network to anything smaller than a zone.
>>>>>> One solution we are looking into is Cisco's 1000v and utilizing
>>>>>> This will allow us scale down the broadcast domains. I don't think
>>>>>> CloudStack has support in configuring their VXLAN settings? Any
>>>>>> comments
>>>>>> or suggestions would be appreciated.
>>>>>> Justin

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