need to replace a switch but l3 or l2?

[m0bov]

Hi all, I inherited at large rather complex network with little documentation.

 

Each wing of the school has a "core" switch, this goes from fibre to copper into various 48port switches, some PoE. All these switches are L3.

 

Now several of these are now starting to fail, mostly fan issues but also PSU issues. The model numbers are 3CR17762-91 and 72-91.

 

I first of all, assumed they would be L2 due to the core switch, so looked at Ubitqui, then when we checked the config of the failing switches, noticed a static route in each one. This goes from the VLANS (wifi, admin ,curric etc.) to the Mgmt Vlan.

 

So I am unsure if we must have L3 or can we go for L2? The same code is in the core switch. Can anyone shed light on this? I've done very little VLAN/L3 myself.

 

James

[localzuk]

I'd suggest that you should take this opportunity to take ownership of the network and rather than simply repeat what they had before look at implementing your own design.

 

I cannot see why a school would have an L3 switch in each wing doing routing - there's not really any value to it. I'd strip it back and have an L3 at the core, and then L2 switches at the edge.

[featured_spectre]

As localzuk has written above, I would have an L3 at the core and manage routing there, and L2 on all outlet wings. It would be a simplified solution to what seems to be a complex problem. It would also make more logical sense.

[m0bov]

We spent sometime this morning looking at it, everything seems up and running now.

 

It appears we have a L3 switch in our comms room (well three).

An L3 switch in each wing of the building (call this the local core switch) with a fibre back to the above comms room

3 or more L3 switches hanging off the local core switch with copper.

All the switches in each wing around the site have ip route-static 0.0.0.0 0.0.0.0 10.211.207.254 coded into them, sending traffic straight to a core switch in the comms room.

 

It does seem totally over the top, a common theme I have found. I am proposing we replaced the x number of access switches with L2 switches and remove the core switch in each wing and put the fibre straight into a L2 switch and then stack the rest. Simplifying the system. What do you think?

[localzuk]

Yeah, that makes more sense. Less complexity for sure.

[m0bov]

They are old 3COM, what's the general feeling for Ubitquity?

[localzuk]

We have Unifi switches in all but 1 of our schools here now. They work well. Though, we still have a HP L3 in the core, as I've not found a reason to replace just yet!

[Davit2005]

Whilst in Campus/University type networks it would be beneficial to move layer3 more to the edge switch I would keep layer 3 at the core in smaller orgs. A couple of HP or other switches that could be stacked for resilience would be my choice in secondary/college sized org. Each edge switch or top of stack switch having a trunk/LAG link to each member of the stack giving resilience/load balancing with out the need for complicated spanning tree setups.

 

In your case, if you are replacing the layer 3 switches you will need to move the Intervlan routing of the vlans to the core, are they all static routes on your core to your satellite L3 switches or dynamic routing protocols?

[m0bov]

Whilst in Campus/University type networks it would be beneficial to move layer3 more to the edge switch I would keep layer 3 at the core in smaller orgs. A couple of HP or other switches that could be stacked for resilience would be my choice in secondary/college sized org. Each edge switch or top of stack switch having a trunk/LAG link to each member of the stack giving resilience/load balancing with out the need for complicated spanning tree setups.

 

In your case, if you are replacing the layer 3 switches you will need to move the Intervlan routing of the vlans to the core, are they all static routes on your core to your satellite L3 switches or dynamic routing protocols?

 

Hi, I will check tomorrow, but we noted all the switches in each edge cab have a static route "ip route-static 0.0.0.0 0.0.0.0 10.211.207.254" set on it, so I think its all being done by the core routering in a main comms room. But will check.

[m0bov]

I just logged into the switches running in the edge cab, both have the same static IP4 route:

0.0.0.0 0.0.0.0 Static 10.211.207.254 (our main core L3) VLAN1

10.211.207.0 255.255.255.0 Direct 10.211.207.55 (the edge cab L3 switch I want to remove) VLAN1

10.211.207.55 255.255.255.255 Direct 127.0.0.1 InLoopBack0

127.0.0.0 255.0.0.0 Direct 127.0.0.1 InLoopBack0

127.0.0.1 255.255.255.255.255 Direct 127.0.0.1 InLoopBack0

[DrBeaker]

As per many other and probably more experienced/knowledgeable posters have already put....

 

Managed Layer 3 at the core, with aggregation switch/function

 

Managed Layer 2, 24-48 ports PoE switches 2 at the edges, full 1Gbps ports, 10Gb SFPs/fibre if possible back to the core switch(s).

 

I'd ideally put a rack-mounted UPS in each edge cab too, but that's simply too much money.

Edited August 27, 2019 by DrBeaker

[m0bov]

Hi yes, agreed looking at doing that and yes, UPS I will try and go for.

[m0bov]

Ok got a meeting tomorrow with a VAR, doing a total overview and scoping and get a short term plan and a long term plan together!