Scanario#21 – VG224 Fax Issues

Posted: August 17, 2010 in Real World Scenarios, VG224
Tags: , , ,

Customer reported a fault that several fax machines which were working fine last week have suddenly stopped working. All they were getting for incoming faxes was just the header. No content of the actual fax.

Rule of thumb – anything which was working before and not working now means something must have changed. I jumped on the main Voice gateway which was connected to the switch and the Fax machines were connected to the VG224. A typical depiction could be as follows:

PSTN >> VGW >> SW >> VG224 >> FAX

There were 3x E1 cards on the Voice gateway. One of them was connected to PSTN which was used for incoming/outgoing calls, the other one was connected to Meridian PBX system and the third one to Investec DealerBoard.

E1 0/0/0 – PBX
E1 0/1/0 – ISDN30
E1 0/2/0 – Dealer Board

I first checked the network-clock-participate and network-clock-select as they are very important for Fax issues. I found  this:
network-clock-participate wic 0
network-clock-participate wic 1
network-clock-participate wic 2
network-clock-select 1 E1 0/0/0

So the Primary clock source was Meridian PBX side. I then checked the controllers and found as follows:

E1 0/1/0  – Connected to ISDN PSTN  – faxes are coming on this line

Total Data (last 24 hours)
0 Line Code Violations, 0 Path Code Violations,
18475 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,
18475 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

LON-VG1-3825#

E1 0/2/0 – Connected to ITS Dealerboard

195 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
Total Data (last 24 hours)
0 Line Code Violations, 0 Path Code Violations,
18701 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,
18701 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

!

I found the issue. The E1 had so many Slip seconds and that was the main reason for fax issues. I later found out that there was some planned work carried out by third party which changed some configuration at the Meridian PBX side. This obviously created some clocking issues. I re-configured the clock-select as follows:

no network-clock-select 1 E1 0/0/0
network-clock-select 1 E1 0/1/0
network-clock-select 2 E1 0/0/0

This way I made the PSTN as main clocking source which eliminated the slip seconds issue and the fax started working.

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Comments
  1. max says:

    And the guru speaks again.

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