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MGCP Enabled VG-224 Port Type

William Bell
VIP Alumni
VIP Alumni

Yes, I am repeating a question I have seen on other netpro threads.  No, I am not a complete idiot.  Though, the question may be considered a lean to idiocy but I'll ask anyway.

So, I see that other folks have posed the question on whether one should pick ground-start, loop-start, or POTS when adding a port to a VG-224 gateway that is configured as a MGCP device in Cisco Unified Communications Manager (CUCM).  In a couple of those threads I have seen people say "always use POTS" or the incredibly information one words response: "POTS".  But I have not seen an explanation as to why POTS versus say loop-start?

I understand the difference between loop-start and ground-start.  What I don't get is why POTS is listed as an alternative to either one of the aforementioned options.  Meaning, I have seen plenty of documentation that explains loop-start as the signaling method normally used by POTS lines.  I never thought of them as mutually exclusive. Can someone help me with what I am missing here?  Clearly there is some difference as the config options for loopstart are different than POTS.

It it helps, I am using the VG-224 for basic analog stations, fax machines (mostly), and modems (POS systems). I am using MGCP because I need CA-controlled T.38 fax relay.

Thanks in advance.


HTH -Bill (b) (t) @ucguerrilla

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1 Reply 1

Aaron Harrison
VIP Alumni
VIP Alumni

Hi Bill

Not sure how much help this is, but the difference I see between the two port types when added to CCM is that the POTS type allows you to specify prefix digits, expected digits etc as with other FXS ports registering via MGCP.

The loop/ground types just have a mandatory 'Attendant DN', as you would get with an FXO port.. implies it would just operate in a PLAR style?

I have to say I can't think of many scenarios where you would have an internal FXS port that couldn't DTMF dial, and I don't have a VG224 handy to actually see what it does...


Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!