Re: Understanding how VLANs work in this system (259 Views)
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Occasional Visitor
ipanema
Posts: 1
Registered: ‎12-29-2013
Message 1 of 2 (294 Views)

Understanding how VLANs work in this system

[ Edited ]

Hi,

 

I'm a beginner in networking and trying to get a hold on how traffic flows in a particular network setup. The network in question has been implemented around an HP 4220vl core switch with L3 routing capability. The edge switch is HP 2510-24.

 

I've modified and simplified the network example to include only parts I considered necessary. Hopefully nothing important is missing. Forum code pasting feature seems terrible, so I've included 4220vl configuration output as an attachment, along with a simple picture of the network. Unfortunately, I don't have access to 2510's configuration right now.

 

What I do know about the global configuration is that all host computers have access to all servers and Internet. Note that I may have excluded VLAN information that has to do with local server-WAN communication - I'm not interested in that at this point.

 

On L2Switch, all connected host computer NICs are 802.1Q-non-compliant, so every port must be (?) set untagged. If ports are untagged in VLAN 10, how can these computers access fileServer or dc01 in different VLANs? I guess what I'm asking is whether L3Switch is capable of routing not only between ip subnets but also between VLANS.

 

My current understanding is, that, based on the fact all host computers can only "talk" untagged, computers are only able to send and receive data in VLAN 10. This is also why having A4 port tagged in VLANs 20 and 30 appears to serve no purpose, as computers would not know how to deal with tagged frames coming through.

 

Please, dear community, enlighten me!

Honored Contributor
Richard Brodie_1
Posts: 583
Registered: ‎10-09-2003
Message 2 of 2 (259 Views)

Re: Understanding how VLANs work in this system

"If ports are untagged in VLAN 10, how can these computers access fileServer or dc01 in different VLANs? I guess what I'm asking is whether L3Switch is capable of routing not only between ip subnets but also between VLANS."

 

The packets for the fileserver go into 192.168.1.2, which presumably is the gateway, and are routed via 192.168.2.1. As these interfaces are bound to different VLANs the packet will cross VLANs, in a similar way to if you had a router with multiple physical interfaces.

 

"This is also why having A4 port tagged in VLANs 20 and 30 appears to serve no purpose, as computers would not know how to deal with tagged frames coming through."

 

That appears to be the case, assuming the configuration on the 2510 is fairly plain. It wouldn't be that unusual to trunk all the VLANs to all the switches, even if they're not needed immediately. The 2510 can always untag them to specific ports, if needed.

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