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My organization's network topology goes like this:

PC -- VoIP -- L2 switch (no IP address, only performs L2 switching)--Network Printer

Also, the same L2 switch is connected to an L3 switch for access to the outside network.

Furthermore, the VoIP is set such that VoIPs share a separate VLAN, while PCs and other devices use 'untagged' VLAN 1.

The problem is that with this topology, the PC cannot even find a network printer, as can be verified from the ping request or ARP table. (No entry that has the mac address or the IP address of the network printer can be seen.)

Weirdly, when I directly connect the PC to an L2 switch, the PC discovers the network printer. Also, the PC can discover other network printers that are reached via the L3 switch and themselves connected to identical L2 switches.

(network printer -- L2 switch -- L3 switch -- another L2 switch -- another network printer)

Furthermore, the PC has no problems accessing Internet, other than the network printer connected to the same L2 switch being inaccessible.

What would be possible issues? I am constrained from doing packet captures by organization policies, so I am left to a few options.

Mike Land
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  • There are other things you can test without needing to scan the network. Can other devices attach to the printer this PC cannot reach? If you put a PC in place of the printer with the same IP settings can you connect back into the first segment and to the problem system? What and how are you doing your vlan tagging? – Rowan Hawkins Aug 08 '21 at 17:43

1 Answers1

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Furthermore, the VoIP is set such that VoIPs share a separate VLAN, while PCs and other devices use 'untagged' VLAN 1.

To clarify, you seem to be running a VLAN trunk to each IP phone - VoIP VLAN tagged, PC VLAN untagged. Furthermore, I'm assuming you're using a 'flat' network with a single VLAN for PCs, servers and printers.

Also, the same L2 switch is connected to an L3 switch for access to the outside network.

Likely also using a VLAN trunk. Whether you use an L2 or an L3 switches for switching doesn't matter. An L3 switch may additionally be used for inter-VLAN routing.

The problem is that with this topology, the PC cannot even find a network printer, as can be verified from the ping request or ARP table. (No entry that has the mac address or the IP address of the network printer can be seen.)

If most other things work for the PC, just not the printer connection, I'd guess it's a bug in the IP phone switch. Those are sadly not uncommon with these devices and I'd recommend using separate connections for PCs and phones generally.

But it's not really possible to say without substantially more information about your network setup (comprehensive diagram and device configs) and some diagnostic tracing. If you cannot be allowed to capture packets on the production network you'll need to recreate the situation in a lab.

Zac67
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