cisco sg350 power problem

[enkli]

I have a Snom phone connected to SG350 PO. Have configured POE per prot limiting and it does not work.

On LLDP the phone does not get IP from DHCP server.

IT shows also invalid signature counter on POE port settings

[Flavio Miranda]

Hi

   The way to go is LLDP as CDP is cisco proprietary.  The phone, or any other device with PoE, needs either CDP or LLDP and on this case, LLDP.

 The problem is that, as per the data sheet, this Phone uses LLDP-MED. Make sure your switch does support LLDP-MED.

Administration > Discovery - LLDP > LLDP MED Port Settings*

https://www.manualslib.com/manual/1399729/Cisco-300-Series.html?page=125 

[enkli]

I have disabled Autovoice VLAN... all devices PCS and phones are on the same VLAN. Autovoice VLAN is on VLAN1.

Should it be the case play with lldp-med settings?

[balaji.bandi]

Invalid Signature Counter—Displays the times that an invalid signature was received. Signatures are the means by which the powered device identifies itself to the PSE. Signatures are generated during powered device detection, classification, or maintenance.

https://www.cisco.com/assets/sol/sb/SG220_Emulators/SG220_Emulator_v1-0-0-18_20140626/help/Power_Over_Ethernet5.html

[enkli]

The phone remains in the state requesting dhcp and it does not get ip. All other brand phones work ( yealink) just snom gives this problem

[Flavio Miranda]

DHCP is a bit different, right? this means that the phone got the power it needs and is trying to communicate with DHCP server.

If you plug another phone or a pc on the same port, doest the DHCP works? 

[enkli]

Yes the PC gets DHCP

[Flavio Miranda]

My suggestion is to use port span on  the switch and analize the packets with wireshark. We need to know where the communication stops. If the Phone is not asking or if dhcp is not responding or yet if both are doing their Jobs but somthing else happens.

[enkli]

The snom phone once worked. I have set port limiting in power and put that to 7W. 

Snom is 802.3 AF swith is 802.3 AT. On some formus I have read the CISCO AF implementation is different form that of the standard.

Some thoughts are also with UDLD config on the switch or IGMP snooping.

I am a litlle bit confused. I also disabled Green ethernet.

[Jitendra Kumar]

Don't be confuse 

IGMP Definition:- 

IGMP snooping allows switches to examine IGMP packets and make forwarding decisions based on their content. You can configure the switch to use IGMP snooping in subnets that receive IGMP queries from either IGMP or the IGMP snooping querier. IGMP snooping constrains IPv4 multicast traffic at Layer 2 by configuring Layer 2 LAN ports dynamically to forward IPv4 multicast traffic only to those ports that want to receive it.

Some applications use a single unicast cluster IP address and multicast cluster MAC address. Multicast traffic addressed to a unicast cluster IP address is forwarded to the last-hop router that is configured with the shared multicast MAC address. To support cluster-addressed multicast traffic, assign a static multicast MAC address for the destination IP address of the end host or cluster.

You can configure the IGMP snooping lookup method for each VLAN. Layer 3 IGMP snooping lookup uses destination IP addresses in the Layer 2 multicast table (this is the default). Layer 2 IGMP snooping lookup uses destination MAC addresses in the Layer 2 multicast table.

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Note

 Changing the lookup mode is disruptive. Multicast forwarding is not optimal until all multicast entries are programmed with the new lookup mode. Also, if 32 IP addresses are mapped to a single MAC address, forwarding on the device might be suboptimal.

UDLD Defination :-

In order to detect the unidirectional links before the forwarding loop is created, Cisco designed and implemented the UDLD protocol.

UDLD is a Layer 2 (L2) protocol that works with the Layer 1 (L1) mechanisms to determine the physical status of a link. At Layer 1, auto-negotiation takes care of physical signaling and fault detection. UDLD performs tasks that auto-negotiation cannot perform, such as detecting the identities of neighbors and shutting down misconnected ports. When you enable both auto-negotiation and UDLD, Layer 1 and Layer 2 detections work together to prevent physical and logical unidirectional connections and the malfunctioning of other protocols.

UDLD works by exchanging protocol packets between the neighboring devices. In order for UDLD to work, both devices on the link must support UDLD and have it enabled on respective ports.

Each switch port configured for UDLD sends UDLD protocol packets that contain the port's own device/port ID, and the neighbor's device/port IDs seen by UDLD on that port. Neighboring ports should see their own device/port ID (echo) in the packets received from the other side.

If the port does not see its own device/port ID in the incoming UDLD packets for a specific duration of time, the link is considered unidirectional.

This echo-algorithm allows detection of these issues:

• Link is up on both sides, however, packets are only received by one side.

• Wiring mistakes when receive and transmit fibers are not connected to the same port on the remote side.

Once the unidirectional link is detected by UDLD, the respective port is disabled and this message is printed on the console:

UDLD-3-DISABLE: Unidirectional link detected on port 1/2. Port disabled

Port shutdown by UDLD remains disabled until it is manually reenabled, or until errdisable timeout expires (if configured).