CCIE Pursuit Blog

January 1, 2008

Internetwork Expert Volume III: Lab 3 – Section 3

3 WAN Technologies

3.1 Point-to-Point

This is a fairly easy task.  You just need to disable Frame Relay Inverse-ARP for all DLCIs except for certain DLCIs.  You’ll need to see which PVC are present on router and then explicitly disable Frame Relay Inverse-ARP for the ones that you do not want to dynamically create a Frame Relay map:

r4(config)#do sh frame pvc | i DLCI
DLCI = 401, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, INTERFACE = Serial0/0
DLCI = 402, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, INTERFACE = Serial0/0
DLCI = 403, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, INTERFACE = Serial0/0
DLCI = 405, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, INTERFACE = Serial0/0
DLCI = 413, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, INTERFACE = Serial0/0

r4(config)#int s0/0
r4(config-if)#no frame inv ip 401
r4(config-if)#no frame inv ip 402
r4(config-if)#no frame inv ip 403
r4(config-if)#no frame inv ip 405

r4#sh frame map
Serial0/0(up): ip 190.1.34.3 dlci 413(0x19D,0x64D0), dynamic,
              broadcast,
              CISCO, status defined, active

3.2 Multipoint

“Configure the routers so that if the DLCIs between them change to inactive or deleted status the interfaces used for the Frame Relay link are brought down.”

Isn’t this just saying to use physical interfaces?

I used the physical interfaces, but IE used point-to-mulitpoint subinterfaces.  I don’t see the difference.  Maybe some future task(s) affect this choice?

3.3 Point-To-Point

Nothing to say about this very basic Frame Relay point-to-point subinterface configuration.

3.4 PPP

“Configure PPP on the Serial connection between r4 and r5.”
“To ensure connectivity across this Serial connection, do not disable the peer neighbor router generated by PPP.”

Note that the connected interfaces are NOT in the same IP subnet.  BUT you will have a host route installed on each side of the link:

r4#sh ip route | i 10.5.5.5
C       10.5.5.5/32 is directly connected, Serial0/1

r5#sh ip route | i 10.4.4.4
C       10.4.4.4/32 is directly connected, Serial0/1

Note that only the host route is installed:

r4#sh ip route 10.5.5.0
% Subnet not in table

r4#sh ip route 10.5.5.5
Routing entry for 10.5.5.5/32
  Known via “connected”, distance 0, metric 0 (connected, via interface)
  Routing Descriptor Blocks:
  * directly connected, via Serial0/1
      Route metric is 0, traffic share count is 1

This is a normal function of PPP.  There is a default command of “peer neighbor-route” configured when you enable PPP.  The trick is not how to enable this feature, but rather how to disable it:

r4(config)#int s0/1
r4(config-if)#no peer neighbor-route
r4(config-if)#do clear ip route *
r4(config-if)#do sh ip route 10.5.5.5
% Subnet not in table

r5(config)#int s0/1
r5(config-if)#no peer neighbor-route
r5(config-if)#do clear ip route *
r5(config-if)#do sh ip route 10.4.4.4
% Subnet not in table

3.5 PPP Authentication

This is a pretty straightforward task that requires you to use PAP with “ppp pap sent-username“on r5.

“r5 should not authenticate r4.”

This means that you only need to turn PAP authentication on for r4.  R5 will send a username and password to r4.  r4 will authenticate r5, but r5 will not authenticate r4.

r4#sh run | sec user|Serial0/1
username ROUTER5 password 0 CISCO
!
interface Serial0/1
 ip address 10.4.4.4 255.255.255.0
 encapsulation ppp
 ppp authentication pap

r5:
interface Serial0/1
 ip address 10.5.5.5 255.255.255.0
 encapsulation ppp
 ppp pap sent-username ROUTER5 password 0 CISCO

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2 Comments »

  1. Just working through this lab myself and did the same as you for 3.2 Multipoint used the physical interfaces have you find out why IE used point-to-mulitpoint?

    Cheers,

    Lee

    Comment by Lee Kite — August 9, 2008 @ 2:30 am | Reply

  2. hello all,

    i tried all possibilities and found that when use sub-int (logical int) its status will be down down if its all DLCIs are deleted or inactive. this not the case with main (physical) interface that does not go into down state even all its DLCIs are deleted or inactive

    Comment by hassan — October 8, 2008 @ 11:33 pm | Reply


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