L1 and Frame-Relay Terminology
- L1 DTE = Data Termination Equipment
- L1 DCE = Data Communication Equipment
- Frame-Relay switch is called the DTE, endpoints are called DCE. This is unrelated to L1 DCE/DTE.
- FR DCE responds to LMI inquiries by sending LMI status, never sends LMI inquiries.
- FR DTE sends LMI inquiries, never sends LMI status.
- DLCIs are only locally significant.
- Because serial interfaces and FR are NBMA networks, there is no ARP flooding to discover neighbor addresses.
- Instead FR relies on inverse ARP to allow clients to notify neighbors of their presence and reply to requests.
- Disabling inverse ARP will disable the notification, these are called dynamic mappings.
- Has to be disabled on all routers to disable automatic learning of mappings.
- Inverse-ARP does not allow self-ping.
int s1/0 encapsulation frame-relay no frame-relay inverse-arp clear frame inarp
- If dynamic mappings have been disabled, static ones need to be created on the clients (R1,R3).
- The broadcast keyword allows broadcast packets over NBMA.
- Only configure broadcast on one statement, preferably the statement that configures the router to ping itself.
int se1/0 ip address 10.0.13.1 255.255.255.0 frame-relay map ip 10.0.13.1 103 broadcast frame-relay map ip 10.0.13.3 103 int se1/0 ip address 10.0.13.3 255.255.255.0 frame-relay map ip 10.0.13.1 301 frame-relay map ip 10.0.13.3 301 broadcast show frame pvc show frame map
- Set encapsulation to frame-relay.
- Configure DCE on interfaces
- Create FR PVCs using either frame routes (FR switching framework) or connections (L2VPN framework).
Create FR PVCs using frame routes on FR Switch:
int se1/0 encapsulation frame-relay frame-relay intf-type dce frame route 103 interface se1/1 301 int se1/1 encapsulation frame-relay frame-relay intf-type dce frame route 301 interface se1/0 103 show frame route show frame pvc
Create FR PVCs using connections on FR Switch:
connect R1-R3 se1/0 103 se1/1 301 show connection all
Frame-Relay with Sub-interfaces
- If sub-interfaces are being used, the DLCI needs to be linked to the sub-interface.
- Inverse ARP configuration is not inherited by sub-interfaces.
- With PTP mode sub-interfaces are configured on the hub, each to single location.
- With PTMP mode a single interface is configured on the hub to multiple locations. Disable split-horizon if using EIGRP.
- The no inverse-arp configuration on the physical interface is not inherit by the sub-interface.
int se1/0.123 point-to-multipoint frame-relay interface-dlci 123 int se1/0.102 point-to-point frame-relay interface-dlci 102 int se1/0.103 point-to-point frame-relay interface-dlci 103
- Use point-to-point sub-interfaces configured with PPP encapsulation.
- Use ip unnumbered in order to enable self-ping.
username R3 password cisco int se1/0.103 point-to-point frame-relay interface-dlci 103 ppp virtual-template 1
interface virtual-template 1 ip address 10.0.13.1 255.255.255.0 encapsulation ppp ppp authentication chap ppp pap sent-username R1 password cisco
username R1 password cisco int s1/1.301 point-to-point frame-relay interface-dlci 301 ppp virtual-template 1 interface virtual-template 1 ip address 10.0.13.3 255.255.255.0 encapsulation ppp ppp chap hostname R2 ppp chap password cisco ppp authentication pap