A good command reference for RIPng is found here. I didn’t know Cisco incorporated IPv6 into its CCNA courses! that demonstrates that Cisco is keeping the value of its certs high in the market. I’m proud to be studying networking in general, and Cisco in particular :-)

Showing RIPng configuration information

show ipv6 protocolsWe can see which interfaces are participating in RIPng

show ipv6 rip RIP_ZONE
displays various information about the RIP_ZONE process:

debug ipv6 rip
– see that link local addresses are used in multicasting
– destination address is multicast FF02::9
In TSHOOT lab, R4 has only fa0/0 in RIPng.
– The split horizon rule is a loop avoidance technique that prevents a route from being advertised out the interface through which it was learned.
A good summary about Route Poisoning and Poison Reverse is given by John on CLN:

Route poisoning
This is a method to prevent routing loops within computer networks. Distance-vector routing protocols in computer
networks use route poisoning to indicate to other routers that a route is no longer reachable and should be removed
from their routing tables. A variation of route poisoning is split horizon with poison reverse whereby a router sends
updates with unreachable hop counts back to the sender for every route received to help prevent routing loops.
When the protocol detects an invalid route, all of the routers in the network are informed that the bad route has a hop
count of 16, which stands for infinity). This makes all nodes on the invalid route seem infinitely distant, resulting
in preventing any of the routers from sending packets over the invalid route.
Some Distance-vector routing protocols such as RIP use a maximum hop count to determine how many routers traffic must go
through to reach the destination. Each route has a hop count number assigned to it which is incremented as the routing
information is passed from router to router. A route is considered unreachable if the hop count exceeds the maximum
Route poisoning is a method of quickly removing outdated routing information from other router’s routing tables by changing
its hop count to be unreachable (higher than the maximum number of hops allowed) and sending a routing update.
In the case of the Routing Information Protocol (RIP), the maximum hop count is 15 so to perform route poisoning on a
route its hop count is changed to 16, deeming it unreachable (sometimes referred to as an Infinite metric) and a routing update is sent.

Poison Reverse
When a router receives a route poisoning, it sends an update back to the router from which it received the route poisoning,
this is called poison reverse.
This is to ensure that all routers on a segment have received the poisoned route information.

Route redistribution into RIPng
We’ll configure it on router R4, because here it is the ASBR between OSPFv3 and RIPng.
We chose metric 10 because Seed metrics should be greater than any internal route metric.
let’s see RIB on our distribution switch DSW2:

Metric 12 = seed metric + hop count
= 10 + routerR4 + switch DSW2
= 12

Redistributing OSPFv3 internal routes into RIPng

As configured in my OSPFv3 post, loopback interfaces on R1 are not advertized as internal routes. Rather, they are redistributed into OSPF.
If we configure “redistribute ospf match internal”, a downstream device will see internal OSPF routes being redistributed, and not OSPF-distributed routes.

Sending a default route into RIPng-(config)# ipv6 route ::/0 Serial0/0
– redistribute it into RIP

the distribution switches get the default route.
Redistributing routes was not enough to successfully ping from DSW2 to DSW1. On point-to-multipoint links and on physical interfaces, check frame-relay mappings. It’s not enough to do static mapping with ipv6 interface addresses; you need to add mappings with link local addresses.
Since GNS3 does cope well with link local addresses, I fixed them on R1, R2, R3 and R4. For example, on R1

(config-if)#interface… (config-if)#frame-relay map ipv6 fe80::2 102
Now DSW2 can ping 2026::12:1

Keyboard Banger

Keyboard Banger is a network engineer from Africa. He has been working in network support and administration since 2008. He started writing study notes about certification exams and technology topics a couple of years ago. When he's not writing articles, he can be found wandering on technical forums.


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