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Beginner

Inquiry about L2/L3 Switch

Hi experts,

 

I would like to ask for advice if we should connect the server to metroE router and broadband router (port forwarding enabled to public IP) with L2/L3 switch as below? Our vendor told us that L2 switch is sufficient. Thx.

SwitchConnection.png

 

 

 

14 REPLIES 14
VIP Advisor

Re: Inquiry about L2/L3 Switch

As per your question, in short, Yes here in this case only for Server L2 is good enough.

BB
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Beginner

Re: Inquiry about L2/L3 Switch

That means default route can be set on L2 switch for Internet traffic routing, right? Thx.

VIP Advisor

Re: Inquiry about L2/L3 Switch

L2 Means there is no Routing inside if you looking to Manage the switch and you need to configure Management IP then you need to configure SVI and Default route.

 

Server Port will be Access port - That belongs to Access port, the SVI will be on your Router as Gateway.

 

 

 

BB
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Hall of Fame Master

Re: Inquiry about L2/L3 Switch

Let me take a slightly different approach in answering the original post. First I would like to do a brief review about the relationship of L2 and L3 switches. Most modern switches are capable of either L2 or L3 and how they operate depends on how they are configured. The main distinction between L2 and L3 switches is how they do their forwarding logic for data flowing through the switch. If a switch is operating as L2 then it looks at the destination MAC address and makes its forwarding decision based on that MAC address. If a switch is operating as L3 then it looks at the destination IP address and makes its forwarding decision based on that IP address.  (and any L3 switch will do L2 forwarding within its connected vlans/subnets) So the decision of whether L2 is needed or L3 is needed depends on whether the switch will need to do L3 forwarding.

 

In the diagram of the original post it is clear that the server has an IP address and its default gateway is on the router. It is also clear that its path to the Broadband router is also within the same subnet. So there is no need for any L3 forwarding decision on the switch. And therefore yes a layer 2 switch would be sufficient for this requirement.

 

HTH

 

Rick

Beginner

Re: Inquiry about L2/L3 Switch

Hi, 

 

Thanks for your reply. Sorry , I still have doubt here.  The server 's default gateway is now pointing to MetroE router LAN IP. For routing internet traffic to the broadband router, how L2 switch can accomplish this if it does not support ip route 0.0.0.0 0.0.0.0 192.168.100.1? Thx.

VIP Advisor

Re: Inquiry about L2/L3 Switch

If the Switch Acting as L2, the Server Gateway always point to Metro Ethernet switch IP address to go out.

 

If you like Switch requirement to be managed, then you can setup a Management Ip with Default gatwayas per requirement.

 

you can use default gateway interface connect to manamgment.

 

 

 

BB
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Beginner

Re: Inquiry about L2/L3 Switch

Hi,

Good day.

The server is now connecting to MetroE router which in turn is attaching to the broadband router. Other than upload the data from internal carparks to the server, the server need to access to the Internet for report download and remote ssh by oversea vendor.  Since the server can only connect to the Internal network but fail to access to the Internet, our vendor suggest to add L2 switch as illustrated at my first post. My doubt is that how the server can route Internet traffic while it can access to the Internet via the L2 switch. Is it possible to add the default route to the broadband router on the L2 switch? Or we need to add a L3 switch instead? Please clarify . Thx.

VIP Advisor

Re: Inquiry about L2/L3 Switch

what is the model of the switch ? post the current configuration

 

As long as they are defaultVLAN1 (by default) it should work, until you have configured any other vlan here ?

or changed port to L3, so kindly post the configuration.

BB
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Beginner

Re: Inquiry about L2/L3 Switch

Hi,

 

The vendor originally proposed 2960X and they said they are sourcing the switch. We haven't got its configuration yet. That means L2 switch can route both internal traffic to internal network through ME router and Internet traffic through broadband router without the necessity of default route? The server can forward internal traffic to the default gateway (=ME router IP) . How about the Internet traffic?

VIP Advisor

Re: Inquiry about L2/L3 Switch

If the Server Point to Gateway as Metro E  Router- M<etro router need to handle the routing process

where to send what packet, if you like internet router, then Metro E router need to add routing table to route the traffic via 192.168.100.1 

 

 

BB
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Highlighted
Hall of Fame Master

Re: Inquiry about L2/L3 Switch

The original poster brings up a complication that we did not adequately recognize in the original post about the server accessing the Internet. So at this point my follow up question would be whether the switch would be able to correctly identify which traffic should go to MetroE router and which traffic should go to Broadband router? (Is it as simple that any packet with destination address in private IP should go to MetroE and any packet with destination address in Public IP should go to Broadband? Or is it more complicated that that?)

 

It seems to me that there are at least 2 solutions that could be implemented. One option would be to make the switch into a L3 switch and provide the switch with routing logic that would identify which traffic should be forwarded to MetroE and which traffic should be forwarded to Broadband. For this option the server would change its default gateway to an IP address configured on the switch. The other option would be to keep the switch as L2, to keep the default gateway of the server as the MetroE router, and to configure a default route on the MetroE router with the Broadband router as the next hop.

 

HTH

 

Rick

Beginner

Re: Inquiry about L2/L3 Switch

Hi, 

 

My vendor said it does not work to add default on L3 switch which conecting to MetroE router & broaband router.

 

Fortunately, our carrier finally agree to add a default route to the MetroIP router where the broadband router is attaching to its one of the LAN port and now the server can reach both Internet network through MetroE router and Internet through the broadband router. Thanks a lot for your advice.

VIP Advisor

Re: Inquiry about L2/L3 Switch

Glad finally you were able to sort the rotuing issue with provider.

 

if this resolved mark as resolved for usefullfor other community members.

 

BB
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Hall of Fame Master

Re: Inquiry about L2/L3 Switch

Thanks for the update. Glad to know that you were able to achieve a solution having the ISP add a route. That is one of the options that I suggested. Nice to know that it worked.

 

HTH

 

Rick

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