Hey All,
I was wondering if someone could answer a few questions for me about distributed switches. I've worked with vmware for a few years now, but believe it or not I've never configured a distributed switch. The environment I work in always used standard switches, and when you deal with folks that have the mentality of "if it ain't broke....", it's easy to become complacent. Everything in my environment is 5.1 by the way.
I'm reading various articles on capabilities now, but I don't have a testing environment to break, so I have to be careful of any changes I make. I figured it was best to ask those familiar with it before deciding on any future changes.
-Do I lose all host based network management (what I'm used to with std switches) as soon as I create a distributed switch?
-Is distributed switching vCenter wide, or can I create multiple distributed switches by cluster, or only with certain subnets included?
-What happens when I add a new host to a cluster with a distributed switch? Does it automatically get configured with the networking capabilities of the distributed switch?
-Are there any gotchas or cons that I should be aware of, either during creation of a distributed switch or in the everyday management of it/them?
-What is the best thing I gain? Worst thing I lose?
Thanks for your input. 
Accepted Solutions
Hi,
To answer you:
1) No you do not lose it all as soon as you create the switch. You can create a vDS (assuming licensing) at any time and configure it/play with it. Until you connect hosts and uplinks to it then it's a fairly useless component in vCenter.
2) A vDS is vCenter wide. However, you can create them individually if oyu want. I.E - One for guest traffic, one for management, one for storage. You can also have them per cluster if you REALLY want, and just add the hosts from that cluster into the particular switch you built. Although that's starting to negate the point of them somewhat.
3) When you add the host you will be asked what uplinks you want to use, if you want to migrate any VMK interfaces from the standard switch and if you want to migrate an VMs. AS soon as that host and it's specific uplinks are on the switch then the host will be able to use the vDS for whatever you have set it up for.
4) Nothing in creating them really. Some people are a bit cautious placing host management (typically vmk0) on them, some people aren't. Typically the rule is that with a vDS you can't manage it if vCenter is down. But with a vSwitch you can login to the host directly and configure it that way individually. There are gotchas in this respect to static port binding on port groups, but it can be worked around by having ephimeral port binding on the management port group. Chris Wahl explains it here better than I've rambled
5) The best thing you can is having centralized management and creation of port groups. Got a new VLAN? Need a new port group? Just create it once for the vDS and it applies to all hosts! Plus, you also can benefit from Network I/O control where you can assign shares to specific types of traffic and other goodies that are not available on standard switches. I'd say you don't lose much, vDS if you have the license and and a fairly large estate are the way to go in terms of management. Trying to think of downsides but I really can't!
Happy to help further!
Hi,
To answer you:
1) No you do not lose it all as soon as you create the switch. You can create a vDS (assuming licensing) at any time and configure it/play with it. Until you connect hosts and uplinks to it then it's a fairly useless component in vCenter.
2) A vDS is vCenter wide. However, you can create them individually if oyu want. I.E - One for guest traffic, one for management, one for storage. You can also have them per cluster if you REALLY want, and just add the hosts from that cluster into the particular switch you built. Although that's starting to negate the point of them somewhat.
3) When you add the host you will be asked what uplinks you want to use, if you want to migrate any VMK interfaces from the standard switch and if you want to migrate an VMs. AS soon as that host and it's specific uplinks are on the switch then the host will be able to use the vDS for whatever you have set it up for.
4) Nothing in creating them really. Some people are a bit cautious placing host management (typically vmk0) on them, some people aren't. Typically the rule is that with a vDS you can't manage it if vCenter is down. But with a vSwitch you can login to the host directly and configure it that way individually. There are gotchas in this respect to static port binding on port groups, but it can be worked around by having ephimeral port binding on the management port group. Chris Wahl explains it here better than I've rambled
5) The best thing you can is having centralized management and creation of port groups. Got a new VLAN? Need a new port group? Just create it once for the vDS and it applies to all hosts! Plus, you also can benefit from Network I/O control where you can assign shares to specific types of traffic and other goodies that are not available on standard switches. I'd say you don't lose much, vDS if you have the license and and a fairly large estate are the way to go in terms of management. Trying to think of downsides but I really can't!
Happy to help further!
Thanks Ryan. Appreciate you taking the time to respond.
Licensing isn't an issue for us, so it's nice to know I can create and play first. My fear was that I create something and affect the network on a mass scale without knowing this new (to me) feature inside and out first.
I initially thought of creating them by cluster because that's how my regions are somewhat divided, and all regions have different subnets. I wasn't sure if it made sense to have one distributed switch with every subnet of every host even if hosts could only use their small subset of available vlans, or if that would get confusing. (this wondering coming from someone who has never seen it and was only imagining what I might be in store for) I suppose if you only attach the uplinks you want to each host, having just one distributed switch would probably be fine.
Yes, I have to read up more on all the networking extras. I'm specifically looking into this because I've heard that distributed switches are better for link aggregation, so that might be a plus for one of the hurdles in our environment.
Thanks again for the help. If I have any other questions, I'll be sure to post em here. 