ENARSI (300-410): Route Redistribution - Theory and Configuration

[Music] hey welcome back to the channel burr buddy this is Kevin I'm not sure when you're watching this but at the time of this recording the world is dealing with Kovan 19 many people are either working from home many are sick many have lost their jobs wherever you are I hope you're healthy and safe for me just to have a bit of certainty in these uncertain times I decided that I'm just gonna continue working my plan for the year and that includes creating at the NRC video training series to help people get their ccmp enterprise certification even though as I record this Pearson VUE just closed their testing centers for a period of time but during this difficult period I'm going to continue to do my thing creating training videos for you and this week's video comes from our upcoming an RC course and it covers the theory and configuration of route redistribution if you find it valuable please do me a favor and give me a like down below and subscribe to see all of our YouTube content as we continue to crank it out for you but for now stay safe and enjoy this video on route redistribution until we have a one routing protocol to rule them all there's a need to have multiple routing protocols peacefully coexist on the same network perhaps company a runs EIGRP and the company B runs OSPF and the two companies merge until the newly combined IT staff agrees on a standard protocol to use if they ever agree on one the routes known to OSPF need to be advertised into eigrp and vice versa this kind of scenario is possible thanks to route redistribution and that's the focus of this video other reasons that we might need to perform a route redistribution include having different parts of your network under different administrative control or perhaps we want to connect out with the network of a business partner and also when we're connecting out to the Internet we might want to advertise our IGP routes our interior gateway protocol routes into bgp our vice versa those are the types of things that route redistribution can help us with now consider the basic topology we see here here we're wanting the OSPF and EIGRP to advertise routes that they know about one another and this concept is called mutual route redistribution and since router r2 has one interface in OSPF and one interface in eigrp it's its responsibility to do the route redistribution that's where all the configurations going to be done and we're going to be doing that configuration coming up in a bit but the primary challenge that we run into when redistributing routes between different routing protocols is the different approaches writing protocols use to measure their metrics for example OSPF uses a metric of cost which is based entirely on bandwidth while ya GRP uses a metric that's by default based on bandwidth and delay and this issue isn't as simple as something like converting currencies between two countries because in that scenario there's a ratio describing the relationship of the two currencies but with route redistribution we don't have a relationship like that so what are we supposed to do well we as administrators can configure the metric assign two routes coming in or from one autonomous system which are being at redistributed into another autonomous system and if we don't bother to do that manually if we don't do that configuration there are defaults those default metrics are called seed metrics and here we see some of those if you take a look at this table we can see that by default a route redistributed into OSPF will be assigned a metric of 20 unless that route is being redistributed into OSPF from bgp in that case it's going to be given a metric of 1 now interestingly both rip and E as Europe II have a default seed metric of infinity meaning that a route redistributed into those routing protocols will be considered unreachable by default so when we're redistributing into rip and yeah GRP especially we want to manually configure what metric gets assigned to those routes the BGP is a bit different it's gonna use whatever the initial interior gateway protocol metric was to begin with because remember bgp is looking at just a single metric instead it goes through a fairly lengthy process of different things that's gonna check like weight and local preference and several other things and that's a look at the basic theory of route registry Bhushan so next let's take a look at a configuration example of mutual route redistribution here's the topology we had earlier and in this topology router r2 is learning routes from r1 v OSPF it's learning routes from r3 via EIGRP and what we're going to do is configure r2 to mutually redistribute routes learn from one writing source into the other writing source and our route redistribution that we do entirely on r2 it's going to use the redistribute command but there's a lot of confusion about this command for example if I'm in the OSPF router configuration mode and I give the redistribute command saying I want to redistribute to EIGRP what am I saying am I saying that I want to redistribute OSPF and EIGRP or do I want to redistribute AI GRP into OSPF well here's the rule I want you to remember when we give the redistribute command under router configuration mode for a specific routing protocol we're saying we want to redistribute routes into that routing protocol so in the example I gave where we're giving the redistribute command under OSPF router configuration mode saying we want to redistribute eh ERP or saying is we want to redistribute ERP learned routes into the OSPF routing process now let's go out to the topology we examine 2n set up mutual route redistribution let's issue the show IP route command on router r2 to see what routes r2 knows about let's do a show IP route and you'll notice that it is learning around from AI GRP we can see those because they're tagged with this decode those are edgy or P learned routes and the O indicates that these networks will learned via OSPF but if I go over to router r1 have I learned anything if I do a show IP route here have I learned anything via a routing protocol at all and the answer is no I haven't r2 is not advertising any networks to me all I know about our networks within the OSPF autonomous system same thing if I go to r3 if I do a show IP route I'm only going to know about routes as part of the eigrp autonomous system so let's take a look and we do this on r2 let's take a look at how we can had route redistribution to tell r2 to take the OSPF routes inject them into eigrp and vice versa and i want to reinforce a statement we made earlier about the seed metric we said that the default metric or the seed metric for EIGRP is infinity so just to prove that initially i'm not going to configure any metrics and i'm just gonna let the default seed metric could do its thing so in route r2 let's go into global configuration mode and I'll say router OSPF our process ID is 1 and I'll say redistribute er GRP autonomous system number 1 and let's do the same thing for EIG RP I'll say router ERG RP autonomous system 1 redistribute OSPF process ID 1 and let's see what happens now and notice I did not specify any metrics at all something else I didn't do when I said redistribute AIG RP 1 I did not give the subnets keyword we typically want to give the subnets keyword because that's going to cause both classful and classless networks to be redistributed however in recent versions of Cisco IOS we might get that added for us automatically let's take a look let's do a show run pipe to section router OSPF 1 and even though I did not say subnets the keyword of subnets got added automatically but your version of Cisco IOS might not do that so I think it's a good practice to usually that's what you're wanting to do usually issue the subnets keyword now let's take a look at the IP routing table on routers r1 and r3 first let's go over to router r1 and let's do a show IP route and we see we have learned some routes via OSPF we see the o and we see that they've been learned with OSPF stuff altmetric of a 20 we didn't set that that was automatically configured for us now notice this e 2 that's telling us that this is an OSP F external route specifically a type 2 external route will be distinguishing between a type 2 and a type 1 external route a little bit later in this video but for now we're just trying to get all the routes redistributed we've got our AI GRP learned routes injected into OSPF let's see if the same is true for router r3 have we learned the OSPF routes have they been injected into EIGRP let's do a show IP route and the answer is no we haven't learned any routes beyond what we already knew and why is that it's that default seed metric of EIGRP it's a seed metric of infinity so when those routes were injected into EIGRP they appeared to be unreachable and to resolve this issue we need to assign a metric to routes being redistributed into EIGRP and if you want to take a note on this there are three primary ways that we can assign a non-default metric to a route that's being redistributed into a routing protocol number one we can set a default metric for all routing protocols being injected into EIGRP number two we can set a metric as part of the redistribute command and third we can set a metric using a route map and to illustrate the first option let's configure the metric to assign all routes being injected into EIGRP to be the same metric it doesn't matter if I'm injecting OSPF or rip or whatever they're all going to have the same metric as their injected into EIGRP to do that let's go back over to router r2 and we'll go into global configuration mode and back into router AI GRP autonomous system one configuration mode and I'm gonna say default - metric and if we use some context-sensitive help it's gonna walk us through the metric components of eigrp first is bandwidth and the unit of measure is in kilobits per second and I'll say that we're working with gig links and a gig is 1 million K so I'll say 1 million so a 1 and 1 2 3 1 2 3 6 zeros after the 1 next we specify delay here the unit of measure is in tens of microseconds and I'll just say we've got very little delay will give a 1 to say we've got a 10 micro second delay next we'll say how reliable this link is and reliability is a number over 255 and if I say 255 that's completely reliable so I'll say 255 next we're going to specify the loading we're minimally loaded is a 1 over 255 I'll say a 1 and even though it's not part of the EIGRP metric formula MTU is there as a tiebreaker and I'll say my MTU my maximum transmission unit is 1,500 bytes which is the default by the way let's end this and even though we used the seed metric of 24 OSPF if I wanted to change it we could in fact let's do that lets go into router OSPF process ID 1 and i'll say default - metric 30 so we'll see that we've made a change when we look at those routes over on R 1 so that's going to be the default metric for OSPF now let's go over to R 3 and see if we've learned in your house let's do a show IP route great news we have router r3 has learned routes originating in the OSPF autonomous system and we know they came from outside ERP because next to the D that indicates the edge ERP we've got this e X and that means ERP external and you remember when we talked about administrative distance we said if a route were redistributed into EIGRP instead of having EIGRP x' normal administrative distance of an ani extra routes have an ad of 170 and we can see that right here this is the new administrative distance because these were injected into EIGRP by the way let's go over to router r1 and see if our cost has changed instead of having a metric of 20 I set the default metric to a 30 let's do a show IP route did that change yes sure did here we see the new default metric of a 30 but let's go back over to router r2 and take a look at a different way of setting the metric for these routes being injected into EIGRP the second option we talked about was we could assign the metric as part of the redistribute command so what I want to do is remove our previous default metric keyword and the redistribute command then I'll put the redistribute command back and it's part of that I'll specify the metric so let's go back into router ya GRP autonomous system 1a configuration mode and I'll say no default - metric and it was one one two three one two three and we had a one 255 and a one and a 1500 let's also get rid of the redistribute command I'll say no redistribute OSPF process ID 1 so we've removed any redistribution configuration for EIG RP now let's do everything with one command I'll say redistribute OSPF process ID 1 and the metric as part of the redistribute command I'll specify the bandwidth I'll give a 1 and then 1 2 3 4 5 6 zeroes for the delay I'll say it's 10 microseconds and since tens of microseconds is our unit of measure I'll give a 1 for the reliability I'll say we're totally reliable that's 255 our load were minimally loaded that'll be a 1 and our MTU is going to be 1,500 let's bounce out of that configuration go back over to router R 3 and we should see the same result we saw earlier if I do a show IP route we should still see those routes we do nothing has changed from the perspective of r3 we just configure things a little bit differently on r2 now let's take a look at the third option for setting a metric on a redistributed route it's to use a route map and route maps are super powerful they can be used for a variety of configurations essentially they can match traffic and then once traffic has been matched we can set one or more parameters for example I could say if I've matched up a packet I could set its next hop IP address and essentially override where the routing protocol is telling me to go but in our context we're focused on using a route map specifically for setting a metric value and here we don't even have to match traffic we can just say set the metric value to this here's how we do that let's go back over to router r2 and in router ERP autonomous system 1 configuration mode let's negate that previous command I gave I'll put an O in front of that and now let's create a route map to do that I'll say route - map and I'll call this set - metric - demo now normally when I create a route map if I've got several different matching criteria I would set a sequence number here so the first sequence number might be a 10 the next one might be a 20 and so on here I'm just doing one thing with the route map so there's really no need to enter a sequence number so I can just press ENTER and I can set let's use some context-sensitive help I can set several different things with a route map like I said it is super powerful here though I want to set the metric and I'll say set metric and I'll give those same metric values for EIG RP that we gave earlier which was 1 million one two three four five six we'll set the delay the reliability the load and the MTU now let's apply that route map to the redistribute command let's go back into router configuration mode for EIG repeat anima system 1 and I'll say redistribute OSPF process ID 1 and I'm going to use the route map that we called set - metric - demo and let's go see did the same thing over on the router r3 did it still work let's do a show IP route command yes indeed we still had those routes redistributed successfully into e edge Europe e now let's go back over to router r1 that lives in our OSPF autonomous system for a moment if we take a look at r1 let's do a show IP route and notice that we've got these e two values next to the routes that we've learned from ERP but notice there's also an option for e 1 so what's the difference well a code of e 2 indicates that the route carries a metric that was assigned by the router performing the redistribution and this router that's sitting between the two autonomous systems r2 in our case it's known in OSPF terminology as an ASB are an autonomous system boundary router and an e2 code means that no matter how many routers we went through since we were advertised by the ASPR it doesn't matter if I went through five other routers that metric doesn't change within the OSPF autonomous system and when we redistribute your routes into OSPF that's what happens by default we're using an external type to a code of e1 indicates that the routers metric is made up of because two signed by the ASB are plus the cost two required to get back to the ASB are now to me that sounds like the e1 route is potentially more accurate however having a code of e1 doesn't really give us any advantage in this case in a simple topology like this where r1 only has one way to get out of the autonomous system there's only one asbr and there's only one way to get to that asbr it really doesn't matter if we use e 1 or e 2 but in a more complex topology I prefer to have a code of e 1 because that's going to be more accurate about the true cost and I want to show you how we can configure route redistribution to specify the code of an e 1 let's go back over to router r2 and we'll go into router OSPF process ID 1 configuration mode and I'll say no redistribute ERP 1 subnets we just got rid of our redistribute command now let's enter a new redistribute come and I'll say redistribute eoj european anima system 1 now i'm going to say the metric type is one let's enter that now let's go back and check out the IP routing table on router r1 before I gave that command notice the cost of these redistributed routes it was a cost of 30 or a metric of 30 because that's the metric that I configured on a router r2 let's take a look now let's do a show IP route and now we have an external type 1 and a 1 code and notice the costs now are the metric it's a 31 it's adding the cost of 1 the cost over a giggling it's adding the cost of 1 that it's gonna cost r1 to get to r2 and to that it adds the metric r2 was advertising which was a 30 so 30 plus 1 gives us 31 I think that's a more accurate representation of what the metric should look like and that's a look at a basic route redistribution configuration [Music] you [Music]

Channel: Kevin Wallace Training, LLC

Views: 12,918

Rating: 4.9739585 out of 5

Keywords: cisco, enarsi, 300-410, 350-401, cisco cert, CCNA, ccnp, ccnp enterprise, route redistribution, seed metric, #kwtrain

Id: dUz-CWp_NaA

Length: 20min 25sec (1225 seconds)

Published: Thu Mar 19 2020