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New Member

Cisco SG-300-20 and Cisco SG-300-28P configuration issue


I was wondering if someone can help me with my configuration issue.

We bought one SG 300-20 switch and three SG-300-28 P. In our office we have Avaya IP Office (IP PBX), a couple of servers, and Avaya 1616 IP phones. We do not administrate Avaya IP Office.

Switch SG 300-20 and switches SG-300-28P were added to network, with their default configuration (No Vlan's), and everything worked (workstations were attached to phones and phones were attached to SG-300-28P, servers were attached to SG300-20). All devices in the office were on network.

Last week we decided to differentiate our network (to segment it). The plan was to use SG-300-20 as L3 device and SG-300-28P as access L2 switches for phones and workstations. SG-300-20 was placed in L3 mode. The servers were added to Vlan 110 (, workstations were connected to the phones (Phones were supposed to be in Vlan 100 (, and workstations were supposed to be in Vlan 1 (native, unttaged)(

We created Voice Vlan 100 on access switches SG-300-28P and ports on which phones were connected with workstation's were configured as 100T, 1U. Ports between switches were trunk ports. LLDP-MED was activated and we didn't add anything.  We used DHCP relaying and it worked cause all devices received their IP addresses as it was supposed to be (phones received and workstations

Servers were connected on Layer 3 switch SG 300-20, and all server ports were configured as access ports (Vlan 110).

Up to that everything was ok.

Problem occured with phones and workstations. Avaya IP Office (IP PBX) was on Vlan 110 (, and phones showed that they were in VLAN 100 (, and workstation was in VLAN 1 ( Everybody received their IP addresses, but then IP phones fell in discovery mode and they couldn't reach Avaya IP PBX which was in other VLAN (VLAN 110- Workstations attached to phones were able to operate normaly, they had network etc.

We tried removing IP phone and just attaching workstation, while placing port on switch as 100 U, and it worked and the workstation was able to reach IP PBX, mainly inter-vlan worked.

Eventualy we did a reset of all configuration,cause phones were unable to register on IP PBX.

I'm not sure why phones cannot reach IP PBX.

I would like if someone could acknowledge configuration on switches which we used or is there some other configuration that will work? 

Thanks in advance.


Cisco SG-300-20 and Cisco SG-300-28P configuration issue

hi have you made sure that you have trunked for all vlans on your trunk links as i had a similar issue because i only trunked for one vlan on the link thinking that it would trunk for all by putting the link into trunk mode?

New Member

Cisco SG-300-20 and Cisco SG-300-28P configuration issue

Yes, i am sure that all vlans were allowed on trunks, that was the first thing I checked.

Did you use same configuration scenario?

Cisco SG-300-20 and Cisco SG-300-28P configuration issue

i have 5 switches four operating in l2 and one in l3 so it is similar however i habe not had the same issue with phones and dhcp relay

New Member

Cisco SG-300-20 and Cisco SG-300-28P configuration issue

Can you plese post brand of IP phones and PBX that you have? Maybe there lies a problem.

Cisco SG-300-20 and Cisco SG-300-28P configuration issue

i currently have one phone and a trixbox as a test system on the network. the phone make is a pollycom but thats testing only

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