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  • Table of Contents
  • Layer 2 Technologies
    • Ethernet Switching
      • L2 Switch Operations
      • Spanning Tree
        • 802.1d – STP
        • 802.1w – RSTP
        • 802.1s – MSTP
      • VTP 101
      • Private VLANs
      • VLANs
      • EtherChannel 101
    • Layer 2 WAN Protocols
      • HDLC
        • HDLC 101
      • PPP
        • PPP 101
        • PPP Authentication - PAP
        • PPP Authentication – CHAP
        • PPP Authentication – EAP
        • PPP Multilink
        • PPPoFR – PPP over Frame Relay
        • PPPoE – PPP over Ethernet
      • Frame Relay
        • Frame Relay 101
        • Frame Relay 102
        • Frame Relay Encapsulations – IETF vs Cisco
        • Multilink Frame Relay
        • Frame Relay Switching
        • Routing over Frame Relay
      • Bridging
        • Bridging on a router
        • MTU 101
    • Wireless
      • Wireless Principles
      • Wireless Implementations
      • Wireless Roaming
      • Wireless Authentication
        • WPA2 PSK
        • WPA2 802.1X
  • IPv4
    • IPv4 Addressing
      • Backup Interfaces
      • FHRP 101
      • DHCP 101
      • DNS 101
      • ARP 101
      • IPv4 101
      • Tunnel Interfaces
        • GRE Tunnels
      • BFD – Bidirectional Forwarding Detection
    • IPv4 Routing
      • How the routing table is built
        • How CEF works
        • Routing Order of Operations
        • NSF – Non Stop Forwarding
      • RIP
        • RIP 101
      • EIGRP
        • EIGRP 101
        • EIGRP Metric
        • More EIGRP Features
      • OSPF
        • OSPF 101
        • OSPF Areas
        • OSPF LSAs
        • OSPF Mechanics
      • IS-IS
        • IS-IS 101
        • IS-IS Mechanics – CLNP
      • BGP
        • BGP 101
        • BGP Attributes
        • More BGP
      • Route Redistribution
      • Policy based Routing
      • PfR 101 – Perfromance Routing
      • ODR
  • IPv6
    • IPv6-101
    • IPv6 Routing
    • Interconnecting IPv6 and IPv4
  • MPLS
    • MPLS 101
    • MPLS L3 VPN
  • Multicast
    • Multicast 101
    • PIM 101
    • IGMP 101
    • Inter Domain Multicast
    • IPv6 Multicast
    • Multicast features on switches
  • Security
    • NAT 101
    • NAT for Overlapping Networks
    • ACLs 101
    • ACLs 102
    • Cisco IOS Firewall
    • Zone Based Firewall
    • AAA 101
    • Controlling CLI Access
    • Control Plane
    • Switch Security
      • Switchport Traffic Control
      • Switchport Port Security
      • DHCP Snooping and DAI
      • 802.1x
      • Switch ACLs
    • IPSec VPN 101
      • IKE / ISAKMP 101
      • IPSEC Crypto Maps 101
      • IPSEC VTI 101
      • DMVPN 101
    • EAP 101
  • Network Services
    • NTP 101
    • HTTP 101
    • File Transfer 101 – TFTP & FTP
    • WCCP 101
  • QoS
    • QoS 101
    • Classification and Marking
    • Congestion Management
      • Legacy Congestion Management
      • SPD – Selective Packet Discard
      • CBWFQ
      • IP RTP Priority
    • Congestion Avoidance – WRED
    • Policing and Shaping
      • CAR 101
    • Compression and LFI
      • Header and Payload Compression
      • LFI for MultiLink PPP
    • Frame Relay QoS
      • Per VC Frame Relay QoS
    • RSVP 101
    • Switching QoS
  • Network Optimization
    • NetFlow 101 – TNF – Traditional NetFlow
    • NetFlow 102 – FNF – Flexible NetFlow
    • IP SLA 101
    • IP Accounting 101
    • Logging 101
    • SNMP and RMON 101
    • Cisco CLI Tips and Tricks
    • AutoInstall
    • Enhanced Object Tracking
    • Troubleshooting 101
    • SPAN, RSPAN, ERSPAN
  • Network Architecture
    • Hierarchical Network Architecture
    • SD Access
    • SD WAN
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  • PPPoFR
  • Ping yourself

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  1. Layer 2 Technologies
  2. Layer 2 WAN Protocols
  3. PPP

PPPoFR – PPP over Frame Relay

PPPoFR

PPP can be used encapsulated in Frame Relay to offer all PPP features over an existing Frame Relay network. The first feature that comes to mind is probably authentication, but PPPoFR can also be used to offer advantages such as Multilink PPP over Frame Relay or PPP compression. Also, PPP can help in situations where point-to-point subinterfaces or inverse ARP cannot be used. PPPoFR will use IPCP instead of Frame Relay’s Inverse ARP to determine how to send an IP packet over the network. It also bypasses issues related to Split Horizons. In order to configure PPPoFR we will need to use a Virtual Template interface and a Virtual Access interface. The Virtual Template interface acts as a PPP interface and all configuration is done on it, but it will always show as down/down. The Virtual Access interface will get its configuration from the Virtual Template and will be the interface that will be up/up if everything works out.

To enable PPPoFR, follow these steps: 1. Enable Frame Relay encapsulation

R(config)# interface SERIAL-INT
R(config-if)# encapsulation frame-relay

2. Enable PPP on the frame-relay interface:

R(config-if)# frame-relay interface-dlci DLCI ppp VIRTUAL-TEMPLATE-INT

3. Then, configure the VIRTUAL-TEMPLATE interface with an IP address and with any other PPP options:

R(config)# interface VIRTUAL-TEMPLATE-IN
R(config-if)# ip address ...
R(config-if)# ppp ...

To verify, you can look at the routing table

R3#sh ip route
Gateway of last resort is not set

     2.0.0.0/32 is subnetted, 1 subnets
C       2.2.2.2 is directly connected, Virtual-Access1
     3.0.0.0/32 is subnetted, 1 subnets
C       3.3.3.3 is directly connected, Loopback0

As you can see, there’s the classic /32 ip route inserted by PPP, but it shows up connected on the Virtual-Access1 interface, not on Virtual-Template1. Also, look at the command below to see that the Virtual-Template interface is down/down while the Virtual-Access interface is up/up.

R3#sh ip int brief | i Virtual
Virtual-Access1            3.3.3.3         YES TFTP   up                    up
Virtual-Template1          3.3.3.3         YES TFTP   down                  down
Virtual-Access2            unassigned      YES unset  down                  down

Ping yourself

To ping yourself in Frame Relay you must have a frame-relay map that points to your own IP. With PPPoFR it gets even more complicated, because the configuration uses a Virtual Acces interface that copies its configuration from the Virtual Template interface. Due to the fact that the Virtual Template interface is always down/down, ping to yourself will fail. The solution is to use ip unnumbered from a Loopback interface or make the virtual-template part of a PPP multilink interface.

PreviousPPP MultilinkNextPPPoE – PPP over Ethernet

Last updated 3 years ago

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