PPPoFR on multipoint sub-interface IE WB volIII Lab 5 Task 3.1


I have seen blogs on this topic dating a few moons back. However, none seem to be answering the basic L3 to L2 resolution issue which I can't figure out. ( I had problems with the OSPF section; the routing table was correctly populated on the hub router, BUT packets meant for R1were ending up at R2 hence I decided to go back to the basics. My gut feeling is that the L3-L2 resolution is not correct)

The scenario is: 

Configure a Frame Relay connection between R1, R2, and R5 using multipoint subinterfaces on each router. Do not use inverse-ARP or more than one frame-relay map command on each router. 

The SG states:

 interface Serial0/0

  encapsulation frame-relay

 !

 interface Serial0/0.1 multipoint

  frame-relay interface-dlci 501 ppp virtual-template1

  frame-relay interface-dlci 502 ppp virtual-template1

 !

 interface Virtual-Template1

  ip address 128.1.125.5 255.255.255.0

 

My question here is how does the router know which dlci to use to reach either 128.1.125.1 or 128.1.125.2 since inverse-arp is disabled?

 

 

Comments

  • Do you have PPP peer route enabled?

    Sent from my iPhone
    Please excuse any mistakes and brevity. 

    On 26 Aug 2012, at 19:43, enyatoti <[email protected]> wrote:


    I have seen blogs on this topic dating a few moons back. However, none seem to be answering the basic L3 to L2 resolution issue which I can't figure out. ( I had problems with the OSPF section; the routing table was correctly populated on the hub router, BUT packets meant for R1were ending up at R2 hence I decided to go back to the basics. My gut feeling is that the L3-L2 resolution is not correct)

    The scenario is: 

    Configure a Frame Relay connection between R1, R2, and R5 using multipoint subinterfaces on each router. Do not use inverse-ARP or more than one frame-relay map command on each router. 

    The SG states:

     interface Serial0/0

      encapsulation frame-relay

     !

     interface Serial0/0.1 multipoint

      frame-relay interface-dlci 501 ppp virtual-template1

      frame-relay interface-dlci 502 ppp virtual-template1

     !

     interface Virtual-Template1

      ip address 128.1.125.5 255.255.255.0

     

    My question here is how does the router know which dlci to use to reach either 128.1.125.1 or 128.1.125.2 since inverse-arp is disabled?

     

     




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  • Oh yes, that's the answer.  Thanks!  Forgot about ppp peer route.  So one part of the puzzle is solved.

    What I don't understand  though is that if I do a trace route from R5 to network 128.1.136.3, the first hop is listed as 128.1.125.2 (and it just loops between R2 and R5). The routing table correctly has 128.1.125.1 as next-hop. Debug ip icmp/ip packet detail on R1 does not show any incoming icmp packets.

  • What do the routing tables on all the devices look like?

    Can you also give a little more detail as to the L1/L2 setup of the devices?

    Thanks

    David

    Sent from my iPhone
    Please excuse any mistakes and brevity. 

    On 26 Aug 2012, at 20:49, enyatoti <[email protected]> wrote:

    Oh yes, that's the answer.  Thanks!  Forgot about ppp peer route.  So one part of the puzzle is solved.

    What I don't understand  though is that if I do a trace route from R5 to network 128.1.136.3, the first hop is listed as 128.1.125.2 (and it just loops between R2 and R5). The routing table correctly has 128.1.125.1 as next-hop. Debug ip icmp/ip packet detail on R1 does not show any incoming icmp packets.




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  • In this lab R5 is the hub with multipoint sub-interface s0/0/0.125. R1 and R2 are spokes configured with point-to-point sub-interfaces, s0/0/0.125 . All routers are configured for PPPoFr. Network 128.1.125/24 is configured on the frame-relay WAN. R1's f0/0.1 ip address is 128.1.136.1.

    The frame-relay cloud is in area 125 and R1's f0/0.1 is int area 0.0.0.0. 

     

    RSRack1R5#sh ip ospf neigh


    Neighbor ID     Pri   State           Dead Time   Address         Interface

    150.1.2.2         0   FULL/  -        00:01:51    128.1.125.2     Virtual-Access2

    150.1.1.1         0   FULL/  -        00:01:51    128.1.125.1     Virtual-Access1

     


    RSRack1R5#sh ip route

    ---snip--

         128.1.0.0/16 is variably subnetted, 4 subnets, 2 masks

    O IA    128.1.136.0/24 [110/2] via 128.1.125.1, 00:21:13, Virtual-Access2

    C       128.1.125.0/24 is directly connected, Virtual-Access1

                           is directly connected, Virtual-Access2

    C       128.1.125.1/32 is directly connected, Virtual-Access1

    C       128.1.125.2/32 is directly connected, Virtual-Access2

         150.1.0.0/24 is subnetted, 1 subnets

    C       150.1.5.0 is directly connected, Loopback0

     

    RSRack1R1#sh ip ospf neigh


    Neighbor ID     Pri   State           Dead Time   Address         Interface

    150.1.5.5         0   FULL/  -        00:01:38    128.1.125.5     Virtual-Access1

     

    RSRack1R1#sh ip route

    ---snip---

    128.1.0.0/16 is variably subnetted, 4 subnets, 2 masks

    C       128.1.136.0/24 is directly connected, FastEthernet0/0.1

    C       128.1.125.5/32 is directly connected, Virtual-Access1

    C       128.1.125.0/24 is directly connected, Virtual-Access1

    O       128.1.125.2/32 [110/2] via 128.1.125.5, 00:14:10, Virtual-Access1

         150.1.0.0/24 is subnetted, 1 subnets

    C       150.1.1.0 is directly connected, Loopback0

     


    RSRack1R2#sh ip ospf neigh

    Neighbor ID     Pri   State           Dead Time   Address         Interface

    150.1.5.5         0   FULL/  -        00:01:51    128.1.125.5     Virtual-Access1

    RSRack1R2#sh ip route

    ---snip---

         128.1.0.0/16 is variably subnetted, 4 subnets, 2 masks

    O IA    128.1.136.0/24 [110/3] via 128.1.125.5, 00:25:23, Virtual-Access1

    C       128.1.125.5/32 is directly connected, Virtual-Access1

    C       128.1.125.0/24 is directly connected, Virtual-Access1

    O       128.1.125.1/32 [110/2] via 128.1.125.5, 00:25:23, Virtual-Access1

         150.1.0.0/24 is subnetted, 1 subnets

    C       150.1.2.0 is directly connected, Loopback0

     

    The routing tables look fine but I can't ping 128.1.136.1 from R5. 


    RSRack1R5# ping 128.1.136.1

     

    Type escape sequence to abort.

    Sending 5, 100-byte ICMP Echos to 128.1.136.1, timeout is 2 seconds:

    .....

    Success rate is 0 percent (0/5)

     

    RSRack1R5#trace 128.1.136.1

    Type escape sequence to abort.

    Tracing the route to 128.1.136.1

     

      1 128.1.125.2 4 msec 4 msec 0 msec

      2  *  *  * 

      3 128.1.125.2 0 msec 4 msec 4 msec

      4  *  *  * 

      5 128.1.125.2 4 msec 4 msec 0 msec

     

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