Specifications

MBG Engineering Guidelines, Release 8.0
14 Solutions To Common Problems
14.1Changing a Cluster Node's IP Address
MBG clustering uses IP addresses to identify each node and to initiate cluster communications connections.
To change a node's IP address, Mitel recommends the following procedure:
1. Make sure that the node to be changed is not the master node. Take ownership from another node if
required.
2. From the slave node to be changed, go to the clustering tab and click on the “Leave cluster” button.
3. Reconfigure the address via the MSL console, and follow the prompts to reboot.
4. Join the server to the cluster.
14.2T.38 Faxing Does Not Work With NAT
Use of T.38 fax is not compatible with NAT. A fax device behind a NAT firewall/router that does not perform its
own NAT traversal may not be able to receive T.38 faxes. It may be able to send them.
During the T.38 setup, the receiving fax listens for incoming tones from the sending fax (no-signal, v21-preamble,
etc), then sends tones in response. However, MBG cannot send media to a device behind NAT until that device
first sends at least one media packet to the MBG. In a T.38 setup, that will never happen, and the sender's tones
are discarded. The call fails (after several retries by the sender).
If the sending fax is behind NAT and the receiving fax is not, the call should work.
It is possible to receive T.38 faxes when behind NAT with certain types of call setup. However, it is not wise to
rely on a certain type of negotiation since T.38 calls can be set up in several ways.
Fax devices that support NAT traversal such as STUN should be able to work around this limitation. They appear
to MBG as a device with a public address, and MBG can send to them without needing to receive a packet first.
Use of G.711 faxing is another option, although it requires a very clean stream. Customers can also use a third-
party fax to email or fax to web service.
Note: This problem does not apply to SIP trunks; there is no NAT on trunks.
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