Using PC Port as redundant link to switch

[lfulgenzi]

I recall a document on CCO that explained how you can use the PC Port as a redundant link for the IP phone used in conjunction with the local power.

Has anyone seen this or have some pointers?

[gogasca]

Hi Lelio,

You should set Forwarding Delay to enabled when you connect both ports to switches for

redundant uplinks. Since the PC port doesn't support PoE, external power adapter is

required.

[lfulgenzi]

That's it, nothing else special? I remember reading that forwarding delay. I'm assuming that it's best to have the vlan on both switches, otherwise the phone would require a restart to get a new IP address?

[gogasca]

You statement is correct.

Just for reference:

Forwarding delay Indicates whether the internal switch begins forwarding packets between the PC port and switched port on your phone when your phone becomes active. When forwarding delay is set to disabled, the internal switch begins forwarding packets immediately. When forwarding delay is set to enabled, the internal switch waits 8 seconds before forwarding packets between the PC port and the SW port. You should set Forwarding Delay to enabled when you connect both ports to switches for redundant uplinks or when you daisy chain phones together.

What is the "point of failure" you are trying to avoid? The cable? The Access port?

From the phone I think you may find it will work from a voice perspective, i.e it will still register and you will get audio.

You may have issues with E911 type stuff and anything that needs CDP.

Would need to check. CVTA is also affected by this.

Also you will need "brick" power as the inline power only works on the switch port. So if the primary link fails, there will be no PoE.

I am also not sure how well the fail over will work as the ARP and CAM tables will need to be refreshed when the MAC address of the default router changes.

You will perform some lab testing and then implement it.

BTW time ago there was an internal discussion in which that parameter will be removed sometime in the future, I believe its not present anymore in CCM 5.X

Regards!