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Layer 3 Edge Switch with /30 Uplink

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Conversationalist

Layer 3 Edge Switch with /30 Uplink

This is regarding using a Meraki Layer 3 switch at the edge of the network, where only a /30 subnet is available for the uplink.

 

There is the issue that both the Layer 3 uplink interface and the Management interface need to point to the same upstream gateway address or that the Management interface cannot point to its own switch as a gateway (however you want to look at it).

 

I have seen several other posts on this.

Does anyone else think this is a serious flaw in the switch design?

 

Some suggestions have been for the ISP to provide a /29 network, or to use an internal Layer 3 device to bounce the edge switches Management interface off of. But these may not always be an option.

 

Has anyone seen where the Management interface and the Layer 3 uplink interface share the same IP address?

I know the docs clearly state to not do this.

I have seen it done, but not sure if there are any issues – like the upstream router ARPing back and forth.

 

Any thought on this?

Any plans from Meraki to address this?

4 REPLIES 4
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Kind of a big deal

Re: Layer 3 Edge Switch with /30 Uplink

I can't see this changing.  You'll need a /29.

 

Trying to apply a design concept (/30) for hardware that works differently is not a flaw in Meraki's design.  It's a design flaw in the network numbering for failing to meet the requirements of the equipment being installed.

Highlighted
Conversationalist

Re: Layer 3 Edge Switch with /30 Uplink

Thanks for the quick response.


Interesting take on the flaw being in the network.

 

I am not aware of any other "enterprise" class switch that has this limitation.

 

Especially when the product guide reads:

easy to manage without compromising any of the power and flexibility traditionally found in traditional enterprise-class switches.

 

But making the Management and L3 interface the same IP does work - I just don't know what if any fallout there is.

Highlighted
Kind of a big deal

Re: Layer 3 Edge Switch with /30 Uplink

>I am not aware of any other "enterprise" class switch that has this limitation.

 

Touche.  I'm not aware of many enterprise solutions that support pure cloud management by the manufacturer directly.  Some of the ones that do - are terrible.

 

 

It's just a matter of viewpoint.

Conversationalist

Re: Layer 3 Edge Switch with /30 Uplink

Thanks

 

I was really hoping to see if anyone else is using the 'single IP' method for both interfaces.

 

Or maybe I am the only one who doesn't follow the rules.

 

To tell the truth, I was in a bind and had to make it work.

New customer asked to have a new site setup just like their others.

And all the other sites were setup like that (so I am not the only one).

ISP only gives a /30 and no other L3 devices on premise.

 

You have to get a little creative to configure it.

The portal will not let you make the Layer 3 interface IP the same as the Management interface IP.

But the local access web page will let you make the Management interface IP the same as the Layer 3.

 

So you have to initially set it up at a different site that already has connectivity, and configure the L3 interface while the Mgmt is different. Then bring the switch to the site and use the local access web page to change the Management interface.

 

I know it's not right, but it seems to work.

 

I don't know if the MAC address of the Management interface is the same as the Layer 3 interface.

And I don't have one to play with right now.

 

Just worry as I stated  - the upstream router might be ARPing all over the place, or Meraki might make a change down the road that really prohibits this.

 

Thanks again for the feedback.

 

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