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:
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.
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.
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
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.
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.
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
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