Configuring Annex G
ANSI T1.617 Annex G (Annex G, for short) defines the way to transmit X.25 packets through frame relay virtual circuits. In an Annex G implementation, the acknowledgement/retransmission and flow-control mechanism used in X.25 are invoked to provide reliable transmission. Annex G can also connect X.25 networks through FR networks. It helps you to migrate from X.25 network to FR network and protects the investment on X.25 effectively.
Configuring an Annex G interface
When you configure an Annex G interface, follow these guidelines:
Because Annex G is not compliant with Inverse-ARP, configure a static FR mapping for the destination IP address.
For the two Annex G interfaces of a virtual circuit, configure one as the DTE and the other as the DCE.
To configure an Annex G interface:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Enable frame relay encapsulation on the interface. | link-protocol fr [ ietf | nonstandard ] | The default setting is PPP. |
4. Create a virtual circuit. | fr dlci dlci-number | This operation also leads you to interface DLCI view. By default, no virtual circuit is created on an interface. |
5. Configure the VC interface as an Annex G interface. | annexg { dce | dte } | N/A |
Configuring X.25 parameters for an Annex G interface
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Create an X.25 template and enter its view. | x25 template name | N/A |
3. Configure X.25 parameters. | See "Configuring LAPB and X.25." | Optional. |
4. Configure LAPB parameters. | See "Configuring LAPB and X.25." | Optional. |
5. Return to system view. | quit | N/A |
6. Enter interface view. | interface interface-type interface-number | N/A |
7. Create a virtual circuit and enter its view. | fr dlci dlci-number | By default, no virtual circuit is created on an interface. |
8. Apply the X.25 template to the DLCI. | x25-template name | N/A |
With FR address mapping configured in FR interface view, packets destined for the destination are transmitted through specific DLCI. With X.25 address mapping configured in X.25 template view, a call to the specific X.25 address is launched before a packet is sent to the destination IP address. IP packets can be transmitted correctly only when both types of address mappings are configured.
The configuration performed in X.25 template view is similar to that performed in X.25 interface view. To establish an X.25 link successfully, the configurations on the devices of both sides must be consistent with each other.