RIPng vs. RIPv2 (Stange Differences) ?????


I am using RIPng (RIP Next Generation). I am comparing it with RIPv2 (RIP for IPv4) and I found some differences.

I did the following lab: 2001:db8:5:5::2/64 2001:db8:2:2::2/64 E0 E1 ---------------------------- R1-------------------------------------------------------- R2------------------------ E0 E1 2001:db8:1:1::1/64 2001:db8:5:5::1/64

I put a sniffer between R1 and R2.

R1 is advertising over E1 (IPv6): Route=2001:db8:1:1::/64 Metric=1 Route=2001:db8:5:5::/64 Metric=1

R2 is advertising over E0 (IPv6): Route=2001:db8:2:2::/64 Metric=1 Route=2001:db8:5:5::/64 Metric=1

I am supprised to see that R1 advertise route 2001:db8:5:5::/64 in the internal network (network between R1 and R2). So does R2 with the same route (2001:db8:5:5::/64) in the internal network.

For IPv4, I have the following results: R1 is advertising over E1 (IPv4): Route= Metric=1

R2 is advertising over E0 (IPv4): Route= Metric=1

As you can see, is not advertising by R1 and R2 in the internal network. So why IPv4 does not advertise in the internet network, and IPv6 advertise 2001:db8:5:5::/64 in the internal network?????

Also, for router R1 network is 1 hop away. But for R1, network 2001:db8:2:2::/64 is 2 hops away. I think both networks ( and 2001:db8:2:2::/64) should be 1 hop away from R1!!!!

Can someone help?????

Thank you very much.


Reply to
Eric Gamess
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Sorry, I did the picture of the laboratory again. Thank you.

| 2001:db8:1:1::1/64 | | E0 Router (R1) | E1 | | 2001:db8:5:5::1/64 | | | | 2001:db8:5:5::2/64 | | E0 Router (R2) | E1 | | 2001:db8:2:2::2/64

Reply to
Eric Gamess

AFAIK the behaviours you are seeing are the expected ones.

RIPng uses link-local addresses, so the neighbours are always on the link. So they will always be on the same local subnet (FE80::10). Notice that this is the route that RIPNG does not advertise. RIPNG will advertise any other IPv6 addresses configured on the common link between neighbours

In IPv4, directly connected routes have a RIP metric of 0; when the route is advertised, the advertising router adds 1 to the metric and sends the route. In IPv6, the same thing happens on the sending router.

However on the receiving IPv6 RIP router, in accordance with RFC2080

"Once the entry has been validated, update the metric by adding the cost of the network on which the message arrived. If the result is greater than infinity, use infinity. That is,

metric = MIN (metric + cost, infinity)"

The cost on the receiving interface is 1 by default and thus you see a metric of 2 in the ipv6 routing table. In IPv6 this "cost" can be modified using the command

ipv6 rip metric-offset with 1 being the default

The same effect would be achieved in IPv4 RIP by configuring

router rip version 2 offset-list 0 in 1

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