A few more OLSR Q's

[Elshar]

Hey, OLSR's been working fine for my test setup for a few days. I put OLSR on the next radio up to get a feel for how the routes propegate and such.

One thing I noticed though is that the new 'edge' router is advertising both the default 0.0.0.0/0 and it's own subnet upstream, when it shouldn't really be as it's within the scope of the default route.


I've also noticed that the main IP on all the interfaces of every router is also being advertised as a /32. So one of the routers at the 'end' of my network has a route table that looks like this (the router this came from is 10.31.3.7):


0.0.0.0/0 10.31.3.1 2 2.000 eth2
10.31.3.0/24 10.31.3.1 1 1.000 eth2
10.30.49.0/24 10.31.3.1 2 2.000 eth2
10.40.2.2/32 10.31.3.1 2 2.000 eth2
10.31.3.2/32 10.31.3.2 1 1.000 eth2
10.31.3.4/32 10.31.3.4 1 1.000 eth2
10.30.49.65/32 10.31.3.1 1 1.000 eth2
192.168.2.1/32 10.31.3.1 2 2.000 eth2
192.168.100.1/32 10.31.3.4 1 1.000 eth2
192.168.17.1/32 10.31.3.1 1 1.000 eth2
Am I going to end up seeing the first IP on every interface on every router as a /32 on every other router on the network? Also, the 10.30.49.0/24 should be covered by the 0.0.0.0/0, shouldn't OLSR be filtering out those redundant routes?

I'm really wanting to put this into production, but I can easily see where we'd be enabling it on 100 or so radios. All of them have 192's on them, sometimes as the main IP which is on the inside of a NAT. I guess my next question is if multiples of the same subnet being advertised will cause problems. As you can see above, the 192.168.2.1/32 is being advertised, and quite a few of our radios use that as well as 1.1, 17.1 and a few others. If possible I'd really like to figure out how to get OLSR to just not advertise those, but so far I haven't seen an option while reading the RFC or the man pages.

Thanks again

[tog]

Am I going to end up seeing the first IP on every interface on every router as a /32 on every other router on the network? Also, the 10.30.49.0/24 should be covered by the 0.0.0.0/0, shouldn't OLSR be filtering out those redundant routes?

Yes, you will. This is just how OLSR works. It doesn't filter out "redundant" routes as there really is no such thing. A more specific route takes precedence over a less specific route so it makes sense to have both of these announcements anyway. If this were one of two nodes on your network announcing 0.0.0.0/0, you'd certainly still want the more specific /24 announced. If your /24 were "rolled up" automatically into the 0.0.0.0/0 route, half your network that's closer to and chooses the other node announcing 0.0.0.0/0 would never figure out how to make it to your /24.

I'm really wanting to put this into production, but I can easily see where we'd be enabling it on 100 or so radios. All of them have 192's on them, sometimes as the main IP which is on the inside of a NAT. I guess my next question is if multiples of the same subnet being advertised will cause problems. As you can see above, the 192.168.2.1/32 is being advertised, and quite a few of our radios use that as well as 1.1, 17.1 and a few others. If possible I'd really like to figure out how to get OLSR to just not advertise those, but so far I haven't seen an option while reading the RFC or the man pages.

Thanks again

Multiple IPs from the same subnet or even multiple same IPs being announced will not cause problems. Never has for me, I keep 192.168.2.1 on ether2 of any board where I'm not using ether2 for something else. So I have 192.168.2.1 announced all over my network. I really don't care about ever reaching any "real" 192.168.2.1 anywhere so it doesn't bother me. OLSR does not care or get confused or anything by all the 192.168.2.1/32s like RIP would. Of course if you ever have a private (or public) IP or subnet that's not behind NAT that you would like to ensure is reachable, you need to make sure it's unique. Don't go assigning 192.168.254.1/30 and 192.168.254.2/30 to every cross-over connection between two boards. Make that sort of thing unique. Keep track of it like you would any other IPs.

[Elshar]

Multiple IPs from the same subnet or even multiple same IPs being announced will not cause problems. Never has for me, I keep 192.168.2.1 on ether2 of any board where I'm not using ether2 for something else. So I have 192.168.2.1 announced all over my network. I really don't care about ever reaching any "real" 192.168.2.1 anywhere so it doesn't bother me. OLSR does not care or get confused or anything by all the 192.168.2.1/32s like RIP would. Of course if you ever have a private (or public) IP or subnet that's not behind NAT that you would like to ensure is reachable, you need to make sure it's unique. Don't go assigning 192.168.254.1/30 and 192.168.254.2/30 to every cross-over connection between two boards. Make that sort of thing unique. Keep track of it like you would any other IPs.

Thanks, that actually answers alot of my questions. Right now we're in the process of putting unique 10.x's on every interface anyways, so the 192s will more or less go away. I've never actually put in routes for 192s either, I've always used them only for customers behind NAT.

The /32 thing is going to bug me though, makes the routing table alot more cluttered than it oughta be. Ah well. :)

[DrLove73]

I am just starting OLSR myself, but multiple /32 seams logical. If you have mesh, you have multiple ways of getting where you need to go. If one of the links goes down, but both ends of broken links are reachable from the rest of the network, it will be still possible po reach BOTH ends by SHORTEST path, and that IS the point, right?

I would of-course like to be corrected if my logic is flawed.

[Elshar]

I am just starting OLSR myself, but multiple /32 seams logical. If you have mesh, you have multiple ways of getting where you need to go. If one of the links goes down, but both ends of broken links are reachable from the rest of the network, it will be still possible po reach BOTH ends by SHORTEST path, and that IS the point, right?

I would of-course like to be corrected if my logic is flawed.

No, you're right. The thing I was thinking is that the router advertises say 10.31.3.1/32, 10.31.3.2/32 and 10.31.3.0/24. Although in a true mesh network you may very well have multiple paths to reach the same segment, so it does seem logical from that perspective.