Tiered Core, Dist, Access layer - SVI configuration.
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08-21-2018 12:27 PM
So, per this architecture, do most usually create all SVIs on the Dist, create all VLANs on Accessswitches, but then what particualar SVIs do most use on Core layers or what is best way to dispurse traffic to the Dist layer from the Cores?
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08-21-2018 12:55 PM
Core, Dist, Access layer is an old design from the 90s. Most networks have just 2 tiers (access and core) as there is no more need for distribution switches. Now, if you already have a 3 tier design and there is not much you can do about it, it is a good idea to have the SVIs for all vlans on the distro and a layer-3 transit links between distro and core. This reduces the size of your spanning tree and lowers the possibility of bringing the whole network down due to a loop.
HTH
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08-21-2018 03:17 PM
Awsome thanks! No this particular project is a lab.
What is you let's say run out of connections on the Cores and let's say you want to add more switches. Should you just choose a couple switches on the Access layer to connect to both for redundancy instead of connecting all the new switches you want to add to all the access layer switches?
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08-21-2018 06:55 PM
What is you let's say run out of connections on the Cores and let's say you want to add more switches.
So, when you design a network, you would count for cases where you may need more switches or connect other devices directly to the core. Usually, you want to leave 25 to 40% room for growth so, the core switches can last you at least 5 years or more. It all depends on the business need and how often the company does lifecycle replacements.
HTH
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08-22-2018 04:30 PM
Also, it is best to hardcode the Cores to be the root bridge for all VLANs on the Cores correct?
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08-22-2018 03:02 AM
As to having "all" VLANs on access switches (even assuming that distribution<>access is L2), you try to restrict VLANs as much as possible. Ideally (with wire-speed L3 switches), the same VLAN doesn't span across a distribution device to more than one logical access switch path.
BTW, Reza is likely correct, most networks, today, are likely 2 tier (core/distro and access), but large(1,000+)/critical LANs sites, will likely be 3 tier, either due to physical equipment limitations or to avoid having L2 in one "core/distro" device.
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08-22-2018 07:55 AM
Yes so I will be doing HRSP SVIs on the cores, the access switches will have SVIs/VLANs for whatever hosts that are connected - access switches point to Cores as GW.
If I am out of ports on Cores and need to add switches to access layer, should I just put all need layer 2 vlans on these switches and trunk them to just 2 access switches for redundancy?
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08-22-2018 12:55 PM
Don't connect the access switches together especially since you are routing at the access layer.
Just make sure the core switches are large enough to handle more access switches (room for growth).
HTH
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08-22-2018 04:24 PM
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08-22-2018 04:27 PM
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08-24-2018 05:33 AM
Could you clarify that statement? If the SVIs on on the cores, with HSRP, and you're routing on the edge access switches, why are you using HSRP on the cores?
"If I am out of ports on Cores and need to add switches to access layer, should I just put all need layer 2 vlans on these switches and trunk them to just 2 access switches for redundancy?"
Will your additional access switches be routing too? Regardless, if you're short core ports, you can treat some existing access switches as hybrid distro/access devices. This can be done with L2 or L3, depending on whether the devices are L2 or L3. If doing L2, again, ideally try to avoid spanning the same VLAN having access ports on more than one upstream device hosting the SVI-gateway.
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08-24-2018 06:37 AM
Could you clarify that statement? If the SVIs on on the cores, with HSRP, and you're routing on the edge access switches, why are you using HSRP on the cores?
So COres will route for all subnets, but access switch that will have additional SVIs (other than same management SVI that is on all switches) will have SVI for only the subnets that hosts are connected to on the particular pair of switches, so they do not have to go to the Core to route between their vlans (e.g VPC Core pair has SVI 1-10, one pair of VPC access switches has SVI 11-15 and a DG to the Core for everything else.
Will your additional access switches be routing too? Regardless, if you're short core ports, you can treat some existing access switches as hybrid distro/access devices. This can be done with L2 or L3, depending on whether the devices are L2 or L3. If doing L2, again, ideally try to avoid spanning the same VLAN having access ports on more than one upstream device hosting the SVI-gateway.
No they will not. I only want to send what ever vlans out the trunks to the access switches that that must be routed at the SVIs on the core. Or would it be better to do SVIs for whatever is needed like I stated above.
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08-24-2018 07:20 AM - edited 08-24-2018 07:21 AM
I'm still a bit lost in what you are asking now.
Normally you would use HSRP with vPC, also assuming the edge was only L2, like on FEXs. But you generally don't use vPC when routing between L3 devices. Also, I wouldn't consider vPC architectures classical 2 or 3 tier. (Much as a leaf/spline architecture isn't classical 2 or 3 tier either.)
If yours is a vPC question, you might want to post a new question.
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08-24-2018 08:33 AM
Should I join the cores into a VPC domain, and then the pairs of access switches into their own VPC domain. Just trunk all uplinks between the switches?
