Wednesday, October 10, 2012

Lab 195 - RIPng Path Selection Using Metric


Prerequisites: CCNP level skills.

Topology

Notice!
In order to proceed to the next lab you must first complete all the previous labs (from lab 188 onwards).

Pic1. IPv6 Topology Diagram.

Task 1
Advertise Vlan 46 into RIPng. Modify metric in R3 so that it uses R4 as its primary gateway towards Vlan 46. In case the connection loss towards R4 down, R6 should be used to reach Vlan 46.

Solution

Task 1
Advertise Vlan 46 into RIPng. Modify metric in R3 so that it uses R4 as its primary gateway towards Vlan 46. In case the connection loss towards R4 down, R6 should be used to reach Vlan 46.

Here, IPv6 global addresses can be anything as the task does mention it.

R4 Config:
!
interface FastEthernet0/0
 ip address 172.16.46.4 255.255.255.0
 speed 100
 full-duplex
 ipv6 address 2001:46:46:46::4/64
 ipv6 rip 346 enable
!

R6 Config:
!
interface FastEthernet0/1
 ip address 172.16.46.6 255.255.255.0
 speed 100
 full-duplex
 ipv6 address 2001:46:46:46::6/64
 ipv6 rip 346 enable
!

Note!
IPv6 RIPng offset-list allows to increment/decrement metric only on per interface basis for the incoming prefixes. Since, R3 uses two DLCIs on the same interface it is impossible to apply larger metric selectively. In order to solve the problem, I have introduced subinterfaces point-to-point as the task does not forbids creating new interfaces.

Before R3 changes the metric its connectivity to 2001:0:0:2E/64 shows two next-hop addresses (pay attention to the metric 2 hops):


R3 Config:

R3(config)#default int s0/1
!
!
int s0/1
 encapsulation frame-relay 
 no ip address
!
int s0/1.34 point-to-point
 ipv6 address FE80::3 link-local
 ipv6 address 2001:0:0:34::3/64
 ipv6 rip 346 enable
 frame-relay interface-dlci 314
!
int s0/1.36 point-to-point
 ipv6 address FE80::3 link-local
 ipv6 address 2001:0:0:36::3/64
 ipv6 rip 346 enable
 frame-relay interface-dlci 316
!

R4 Config:

R4(config)#default int s0/0
!
!
int s0/0
 encapsulation frame-relay
 no ip address
!
int s0/0.34 point-to-point
 ipv6 address FE80::4 link-local
 ipv6 address 2001:0:0:34::4/64
 ipv6 rip 346 enable
 frame-relay interface-dlci 413
!

R6 Config:

R4(config)#default int s0/0
!
!
int s0/0
 encapsulation frame-relay
 no ip address
!
interface Serial0/0.36 point-to-point
 snmp trap link-status
 ipv6 address FE80::6 link-local
 ipv6 address 2001:0:0:36::6/64
 ipv6 rip 346 enable
 frame-relay interface-dlci 613
!

Finally, changing metric on R3 in such way, it prefers R4 as its primary gateway towards Vlan 46.

R3 Config:
!
interface Serial0/1.36 point-to-point
 snmp trap link-status
 ipv6 address FE80::3 link-local
 ipv6 address 2001:0:0:36::3/64
 ipv6 rip 346 enable
 ipv6 rip 346 metric-offset 3
 frame-relay interface-dlci 316 
!

R3#clear ipv6 rip

Verification:
Before shutting down S0/1.34:

Pic. 2

After shutting down S0/1.34: 

Pic. 3