Fooling around with rip - again

Hi all,

Again, I was fooling around with rip.

This time i made a loopback interface with 192.110.1.1/16.
First off, i thought version 1 would just summarize it to 192.110.1.0, but it turns out that rip version 1 wont advertise anything when its that supernet. Also, version 2 will send it with as 192.110.0.0/16 correctly, but the metric will be set to 0:

*Mar 1 00:40:11.799: RIP: sending v2 update to 224.0.0.9 via Serial0/0 (192.168.12.1)
*Mar 1 00:40:11.803: RIP: build update entries
*Mar 1 00:40:11.807: 192.110.0.0/16 via 0.0.0.0, metric 0, tag 0

Anyone else find this strange?
Is this general behavior with RIP v2. and "supernets"?

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Comments

redwarrior

kp, I have no answer for you or anything intelligent to add except that I had to snicker when I heard you were fooling around with RIP...don't you think OSPF will get jealous?

Good luck in your quest for an answer, though...maybe after I'm done with BCMSN and on to BSCI I'll be able to offer more than the humor of a 12-year-old.

Mrock4

Per Cisco: Supernet advertisement is not allowed, other than advertising a supernet learned in the routing tables. Essentially what they're saying is, if the supernet is learned by another means (redistributed, static route, etc), then it can be advertised via RIP, but otherwise it will not. If you enabled PPP over your links, the network should appear as a subnetted network, in which case RIP would advertise. Of course this is "should"..

Let's say you have 2.0.0.0/6 in RIPv2, a summary address wouldn't work, but a static null route (for prefix) + redist static would advertise it. It's a workaround, but it works.

joshgibson82

If the route is local to the box, then the correct metric would be 0, right? It is 0 hops away. Check the first router down stream to see if the metric shows 1. If it still shows 0, then I don't know.

kpjungle

joshgibson82 wrote: »

If the route is local to the box, then the correct metric would be 0, right? It is 0 hops away. Check the first router down stream to see if the metric shows 1. If it still shows 0, then I don't know.

No, RIP would send the advertisement with the hop count it "thinks" the next hop router should use, ie. 1.

kpjungle

Mrock4 wrote: »

Per Cisco: Supernet advertisement is not allowed, other than advertising a supernet learned in the routing tables. Essentially what they're saying is, if the supernet is learned by another means (redistributed, static route, etc), then it can be advertised via RIP, but otherwise it will not. If you enabled PPP over your links, the network should appear as a subnetted network, in which case RIP would advertise. Of course this is "should"..

Let's say you have 2.0.0.0/6 in RIPv2, a summary address wouldn't work, but a static null route (for prefix) + redist static would advertise it. It's a workaround, but it works.

Cool, so there is there some docs refering to it, you have a link or something? again, version 2 will advertise it, but ofcourse not as a true "major" net, since the supernet is too large for it. Same for EIGRP btw, it will advertise it.

Red: noone says I cant play around with both, as long as BGP dont catch me in the act

Mrock4

kpjungle wrote: »

Cool, so there is there some docs refering to it, you have a link or something? again, version 2 will advertise it, but ofcourse not as a true "major" net, since the supernet is too large for it. Same for EIGRP btw, it will advertise it.

Red: noone says I cant play around with both, as long as BGP dont catch me in the act

KP,
The workaround with the static null route + redistro came from a buddy of mine, I can't seem to find something on that, but the article where cisco talks about supernets briefly is actually on summary addresses. It is:

IP Summary Address for RIPv2 - Cisco Systems

I'll look for something else in the meantime.

kpjungle

Mrock4 wrote: »

KP,
The workaround with the static null route + redistro came from a buddy of mine, I can't seem to find something on that, but the article where cisco talks about supernets briefly is actually on summary addresses. It is:

IP Summary Address for RIPv2 - Cisco Systems

I'll look for something else in the meantime.

Thanks alot m8!