Configuring permanent link function at ISDN BRI link layer
With the isdn q921-permanent command, the BRI interface sets up a data link connection automatically and maintain the connection even when no calls are received from the network layer. If the two-tei mode is also configured on the interface, two such connections will be present.
To ensure the success of every call attempt, configure permanent Q.921 link mode where the ISDN NI protocol is adopted.
On PRI interfaces, Q.921 layer negotiates to enter multi-framing state immediately after the user side and the network side are correctly connected. On BRI interfaces, however, the Q.921 layer transits to the multi-framing state only after a call is placed and the Q.921 link that has been set up will be torn down if no Layer 3 call is received before the T325 timer expires.
To configure Q.921 permanent link mode for an ISDN BRI interface:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter BRI interface view. | interface bri interface-number | N/A |
3. Set the Q.921 link on the BRI interface in permanent state. | isdn q921-permanent | The Q.921 links on BRI interfaces are not in permanent state by default. |