Re: [WISPA] OSPF Tutorial/Guide
On 07/20/2013 12:43 PM, Chris Fabien wrote: I have a bench setup running based on the Mikrotik Wiki example, it's running and working, but I'm stuck on the part where I assign cost/distance/priority or whatever the term is to make it decide one link over another. I'm not really grasping how that works. In ospf, the path cost determines where a packet is routed. Take this simple example: -- R2 -- | | R1 - - R4 -Target | | -- R3 -- If, on the R1-R2 interface, you add cost and all other settings are left at default then the traffic at R1 destined for the networks beyond R2/R3 would prefer the path that includes R3, since the cost is higher going through R2 interface. Note that this cost is calculated on the OUTGOING interface, so this example assumes you have one interface for R2 and one for R3. Additionally, because the outgoing path is the one where cost is calculated, the return traffic would consider both the R2 and R3 path to be equal. The essence of path cost is this: higher cost = less preferred path To calculate the path cost (from R1), the router would look at the cost of the interface: R1-R2, R2-R4 and compare it to R1-R3, R3,R4 path. Distance is the metric that the kernel uses to determine which learned route to use. You can google the default route distance to see the full chart. Connected routes are distance 0; Static routes default at distance 1 and ospf learned routes are distance 110. What this means is that a route learned by ospf will be used ONLY if there is no other shorter distance route installed. In RouterOS, you can change the distance for static routes, so that you can use them as backup in case OSPF fails. The OSPF priority parameter is only used to determine which router in a segment becomes the DR, BDR or just another router. You can google ospf designated router election to see exactly how this happens. I want to be able to assign priority to the links so that it won't always take the least # of hops path, we have a redundant link between two main towers which is an old nanobridge link and want to reserve it as the backup link. You are probably looking for cost instead of priority. Just for the record, this is one of the things we cover in my classes. There is one lab that we do that covers all of these things in great detail. -- Butch Evans 702-537-0979 Network Support and Engineering http://store.wispgear.net/ http://www.butchevans.com/ ___ Wireless mailing list Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless
[WISPA] OSPF Tutorial/Guide
I need to get OSPF running on the network linking our 4 core towers - had a heat related failure on a mikrotik radio cause an outage this week. We have enough links that we could set this up for redundancy but only have static routing in place, so I had to manually route around the down link. I have a bench setup running based on the Mikrotik Wiki example, it's running and working, but I'm stuck on the part where I assign cost/distance/priority or whatever the term is to make it decide one link over another. I'm not really grasping how that works. Any suggestions for a tutorial or documentation which explains that, or if it's simple, maybe just tell me what I need to do? I want to be able to assign priority to the links so that it won't always take the least # of hops path, we have a redundant link between two main towers which is an old nanobridge link and want to reserve it as the backup link. Thanks for any advise! ___ Wireless mailing list Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless
Re: [WISPA] OSPF Tutorial/Guide
If you set each and every backhaul/link to 10 cost and there are three backhauls between towers you have 30 cost. If that last tower has another option to the first tower with only one link and the cost is 10, it'll use the 10 instead of 30. If the cheaper 10 is down, it will use the 30 cost path. You can set them all to 10 and then if you want a particular path to be used more, reduce the cost. Same goes the other way around. Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Sat, Jul 20, 2013 at 1:43 PM, Chris Fabien ch...@lakenetmi.com wrote: I need to get OSPF running on the network linking our 4 core towers - had a heat related failure on a mikrotik radio cause an outage this week. We have enough links that we could set this up for redundancy but only have static routing in place, so I had to manually route around the down link. I have a bench setup running based on the Mikrotik Wiki example, it's running and working, but I'm stuck on the part where I assign cost/distance/priority or whatever the term is to make it decide one link over another. I'm not really grasping how that works. Any suggestions for a tutorial or documentation which explains that, or if it's simple, maybe just tell me what I need to do? I want to be able to assign priority to the links so that it won't always take the least # of hops path, we have a redundant link between two main towers which is an old nanobridge link and want to reserve it as the backup link. Thanks for any advise! ___ Wireless mailing list Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless ___ Wireless mailing list Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless
Re: [WISPA] OSPF Tutorial/Guide
Cost is what is used for determining routes. Priority is for who has the the more important information. Typically we leave the priority at default. Set the cost on the backup links higher than the cost on the primary links. On 7/20/2013 1:43 PM, Chris Fabien wrote: I need to get OSPF running on the network linking our 4 core towers - had a heat related failure on a mikrotik radio cause an outage this week. We have enough links that we could set this up for redundancy but only have static routing in place, so I had to manually route around the down link. I have a bench setup running based on the Mikrotik Wiki example, it's running and working, but I'm stuck on the part where I assign cost/distance/priority or whatever the term is to make it decide one link over another. I'm not really grasping how that works. Any suggestions for a tutorial or documentation which explains that, or if it's simple, maybe just tell me what I need to do? I want to be able to assign priority to the links so that it won't always take the least # of hops path, we have a redundant link between two main towers which is an old nanobridge link and want to reserve it as the backup link. Thanks for any advise! ___ Wireless mailing list Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless No virus found in this message. Checked by AVG - www.avg.com http://www.avg.com Version: 2013.0.3349 / Virus Database: 3204/6506 - Release Date: 07/20/13 -- Scott Reed Owner NewWays Networking, LLC Wireless Networking Network Design, Installation and Administration Mikrotik Advanced Certified www.nwwnet.net (765) 855-1060 (765) 439-4253 (855) 231-6239 ___ Wireless mailing list Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless
