Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring DDN or BFE X.25Configuring X.25 and LAPBlocal-cug 300 network-cug 33local-cug 5000 network-cug 55, preferentialTroubleshooting Tips for X.25 CUG ServiceYou can use debug x25 events command to verify if and when CUG calls are being made and how theCUGs are behaving. The following example shows messages concerning a rejection of a call by a DCEbecause CUG 40 is not configured at the DCE interface, either by design or by administrative mistake:Router# debug x25 events00:48:33:Serial1:X.25 I R1 Call (14) 8 lci 102400:48:33: From (3):111 To (3):44400:48:33: Facilities:(2)00:48:33: Closed User Group (basic):4000:48:33: Call User Data (4):0x01000000 (pad)00:48:33:X.25 Incoming Call packet, Closed User Group (CUG) protection, selected networkCUG not subscribed00:48:33:Serial1:X.25 O R1 Clear (5) 8 lci 102400:48:33: Cause 11, Diag 65 (Access barred/Facility code not allowed)Configuring DDN or BFE X.25The Defense Data Network (DDN) X.25 protocol has two versions: Basic Service and Standard Service.Cisco System’s X.25 implementation supports only the Standard Service which also includes BlackerFront End (BFE).DDN X.25 Standard Service requires that the X.25 data packets carry IP datagrams. The DDN packetswitching nodes (PSNs) can extract the IP datagram from within the X.25 packet and pass data to anotherStandard Service host.The DDN X.25 Standard is the required protocol for use with DDN PSNs. The Defense CommunicationsAgency (DCA) has certified Cisco Systems’ DDN X.25 Standard implementation for attachment to theDefense Data Network. As part of the certification, Cisco IOS software is required to provide a schemefor dynamically mapping Internet addresses to X.121 addresses. See the section “Understanding DDNX.25 Dynamic Mapping” that follows for details on that scheme.To enable DDN X.25 service, refer to the following sections:• Understanding DDN X.25 Dynamic Mapping• Enabling DDN X.25• Defining IP Precedence HandlingTo enable BFE X.25 service, perform the task in the following section:• Configuring Blacker Front End (BFE) X.25Understanding DDN X.25 Dynamic MappingThe DDN X.25 standard implementation includes a scheme for dynamically mapping all classes of IPaddresses to X.121 addresses without a table. This scheme requires that the IP and X.121 addressesconform to the formats shown in Figure 44 and Figure 45. These formats segment the IP addresses intonetwork (N), host (H), logical address (L), and PSN (P) portions. For the BFE encapsulation, the IPaddress is segmented into Port (P), Domain (D), and BFE ID number (B). The DDN algorithm requiresthat the host value be less than 64.54