3. Static RP
Now, in the previous section we have seen some of the basic IP Sparse mode configuration with rps. Now RP stands for Random Point and RP is the root of the Shadery and the RP is going to learn about the source and the receivers. Like we must configure an RP, RP is going to learn from where the source is sending a multicast traffic based on some pim register messages and the receivers the routers has to join to the RP by using pim joint messages and then it’s going to build some Escomma geentries from source to RP and receiver to RP. And then the receiver is going to build the shortest part of the source and it’s going to send out the pruned messages to the RP to stop the multicast traffic. Now, that is something we have seen much more in detail in the previous sections.
Now, what if there is no RP? Now, if there is no RP, the source will not be able to register themselves and there won’t be any joint messages process. So if you’re using ipm Sparse Mode then it’s really mandatory. You need to have an RP. Now, in this section we’ll get into some of the different ways to configure the RP. Now, there are two major different ways to configure the RP. Either we can go to each and every router, we can define an RP address, that’s what we call as Manual RP or static RP. Or we can configure the routers to automatically learn about the RP information. Now, either by using a cisco proprietary method, that is auto RP method, which is a legacy no more used, or we can go with the pim standard method, that’s what psr method. So we’ll get into more in detail on these things.
Now, right now we’ll talk about static RP. Now, static RP is possible to configure an RP for a multicast group purchase like normally. What we need to do is here we need to configure the manual RP on each and every router and we can have a common RP for all the routers. Now, it is the more simplest way to define the RP in a small size networks. But this manual RP is not scalable for large and complex networks. Now, the main reason is we need to go to each and every router and we have to configure the RP by using this command. And this command has to be configured on each and every router. And the one more condition is all the routers must have the same rpo. And if the manual configured RP now all the routers must have the same RP address and every router must use the same RP address.
Now, in case if there is any change in the rps, it needs a reconfiguration on each and every router. And there is one more disadvantage with the static RP is there is no failover possible. Now, failover means let’s say if I have configured an RP maybe a router three as an RP. Now, due to some reason this RP fails, there is no failover procedure to take over the function of the failed RP. So we need to ensure that RP must be available all the time in order for all the source and the receivers to register themselves with the RP. The configuration wise, it’s going to be very simple and straightforward. We need to ensure that we are enabling sparse mode on all the routers. And all the interfaces must be enabled with multicast by using this IP pimp pass mode commands.
And we need to go to each and every router. In my scenario, we need to go to router one, router two, router three, router and router five. On all the routers. We need to define the RP address. Now, the RP address can be any interface and we just need to ensure that that particular RP address must be reachable via igp. So because of that RP of check now this something the configuration of the status RP we have seen already in the previous lab in the ippins pass mode. So we are not getting into the lab. A practical implementation of this. So probably in our next section videos, we’ll be getting into some of the other methods of learning the RP which are more commonly used. That is your Auto RP and the bsr RP candidates.
4. Auto RP
Now, in this video, we’ll see how Auto rp is going to work. We just get back to some of the basics, what we have seen in the previous videos. Like we must configure the rp in your Pim domain so that every source can send their Pim register messages and also the receivers can send some join messages. So rp is something we must configure if you’re using IP pims pass mode. So that the shortest part three is built. Now, there are multiple ways to configure the rp. Either we can manually define the rp by going to each and every router. That’s what we have seen, a static rp. But static app is something not scalable in a large and complex networks. Now, we can go with something called Dynamic rp configuration. And that can be done by two different ways.
Either we can use a cisco proprietary method of advertising the rp information, or we can use a standard method of advertising the rp information. Now, in this video, we’ll see how the Auto rp is going to work, which is a cisco proprietary feature. Now, Auto rp is a method of providing the information about the rp to all the remaining routers. So all the routers are going to learn about the rp information automatically. Now, there are two different devices or the roles which will make this possible. And that is one is Candidate rp and Mapping Agent. Now, in this setup, we need to configure any one router as an rp. Like, let’s take an example. I’m going to configure the router three as an rp and that will be referred as candidate rp. Now, candidate rp is like the device who is advertising itself as an rp or willing to become an rp.
Now, in my scenario, I’m going to configure the router three lowback zero three one as an rp information. So it’s going to advertise to the rest of the domain saying that it’s an rp on subtros. Now, the mapping agent is the one who is going to listen to that rp advancements and it’s going to provide the information to the rest of their Pim domain. So which means the mapping Agent, let’s say in my scenario, I’m going to configure the router four as a mapping agent and it’s going to listen to that particular rp messages and it’s going to provide that information to all the remaining routers. So here in my scenario, the router one will automatically come to know that the router three is an rp based on information provided by the mapping agent. Now, it’s not mandatory that you must use different routers for rp and Mapping Agent.
You can still make the same router to be configured as rp as well as the mapping agent. Now, here are two different roles. One is Candidate rp and the other one is Mapping Agent. Now, let’s see how it works. We’ll get into the configuration wise. It’s just a two line commands. We’ll get into this configuration more in detail in the next video, probably here, we’ll quickly try to understand how the rp auto rp is going to work. Now, just now I discussed that the rp is going to advertise itself as an rp. So it is going to advertise by using some multicasters. So it’s going to say that I am an rp. In this scenario, let’s say this is my candidate rp and this candidate rp is going to advertise information on 224-0139. So as an rp for so and so specific group address.
And it is saying that I’m the rp for so and so specific group address. And the mapping agent is going to listen on this on this particular address. Now, the mapping agent here is going to listen to these messages and it’s going to figure out the rp. And the mapping agent is going to generate an advertisement using 224 dot zero, dot one, dot 40 to distribute the rp mapping informations. So it’s something like the rp is going to advertise the information on 224-0139 and then mapping agent is going to advertise on 40. So all the routers, all the remaining routers, they listen on 224-122-4014 and the mapping agent is going to listen on 224-0139. That’s a very simple and straightforward concept where rp will advertise its own information on 39 multicast address and 224-0139.
And the mapping agent is going to listen on this particular address. And then all the remaining routers are going to listen on 2240 140, whereas the mapping information is going to provide the rp information on this address and all the remaining routers in the Pim domain list on this particular address. Now, this is very important for me to know, because before they actually learn about the rp information, they must know how to reach these multicasters. So probably this something will get into more in detail in the next video where we’ll see the configuration of Auto rp. Now, the configuration is very simple and straightforward. We just need to go to the router. Now, whichever router we want, we decided to use an rp.
Like here. In this scenario, I decided to use router three as an rp and we need to say IP pim Send rp announced. So whenever you send rp announce, it’s nothing. But we are advertising that this router is an rp and we are using the low back zero interface. And then the scope scope is more similar to your ttl value, the number of hops. This information has to be propagated. Now, whatever the router you decided to use as a mapping agent, like in my scenario, I decided use the same router as a mapping agent. We need to say, send rp discovery. Now, Send rp Discovery message is used to configure the mapping agent. And whereas Send rp announced is the command to use to configure the rp rp, there is a random point or candidate rp. So we can send.
5. Auto RP Configuration
Now, in this video we’ll see the configuration of auto rp. Previous videos we have seen the behavior of the auto rp. Now we can configure any specific router as an rp and then mapping agent. Now, rp is going to advertise itself as an rp, whereas mapping agent is going to provide the rp information to the rest of the domain. Now, to practically verify this, I’m going to use the same lab with fire routers and on all these routers. And the first step I’m going to configure is IGP by using ospf area zero. And I already did the IGP configuration just now. If you verify on the router phone, if I go show ipospf neighbor, I can see the neighbors.
And if you verify the routing table, I have utilized all the connected interfaces as per the diagram. Now the second step is we are going to enable IP pim sparse mode and we want to configure the rp based on auto rp configurations. So let’s go to router one and quickly configure the multicasting and then interface f zero by zero IP PMS pass mode. On the router one, I got s one by zero as well, and also I got s one by one. Now, once we configure this, let’s copy paste the same commands because on the router two also I got the same interfaces. And on the router three also I got the same interface name. And then on the router four, also on the router four, also I got the same interfaces. I got one more extra interface s one by two, which is connecting to router phi.
And then on the router phi, also I got IP multicast routing and then interface f zero by zero, I’m going to configure ippim’s pass mode and s one by zero ippim’s pass mode, I got just only two interfaces on the router five. Now they should establish a neighbor relationship. So to verify that, I’m going to use show IP pim neighbors. Now on the router four, I can see three pim neighbors a similar way. I’ll check on the router two, show IP pim neighbors. Show IP p pim neighbors. On the router two, I should say two neighbors. And I enable all the interfaces. So if the neighborship is not coming, just ensure that that particular interface is enabled with IP pim sparse mode or not.
Now the third step, we are going to simulate a client receiver on this interface, which is going to join the group for 224 five. Now we are going to simulate on the router file a client. And for that we are going to use the same commands IP IGMP join group and we are going to say 224. Now, this is the way we simulate a receiver on that particular interface. Now, the next thing is if you try to generate the traffic from the router one, you will not be able to ping to this multicast group address on the receiver and the reason is we don’t have rp. Now we need to configure the rp. We have seen some static rp configurations in our previous videos with static rp also. Now, here we want to decide the rp based on the cisco proprietary method, that is auto rp.
Now, the configuration wise, there are two specific commands we need to configure. Now, we need to go to the router whatever the router you decided to go with rp. Like in my scenario, I’m going to use the router three loop bag zero will be selected as a rp. And we need to configure this command IP pim send rp Announce and the loopback zero. And we need to define the scope. Scope is more like ttl value. It defines how many hops this rp information has to be propagated. And then we also need to configure the mapping agent. Now, mapping agent can be the local router. The same router can be an rp as well as a mapping agent, or you can make any other router as a mapping agent also. Now, to configure the mapping agent, in my scenario, I’m going to make the router three loop bag zero will be custom as a mapping agent also.
And to configure the mapping agent, we need to say Ipm Send rp Discovery messages. So Send rp Discovery messages is to advertise itself as a mapping agent. And whereas Send rp Announce is used to advertise itself as an rp. So let’s go to router three and configure the same on the router three. I’m going to say now before you configure this, just ensure that whatever the interface you have decided to use as an rp, that interface has to be enabled with IP pim Spark Mode. And also that interface has to be advertised inside your IGP. Now in my scenario, I’m going to advertise an IGP, because normally, if you remember we discussed that in the case of Pim register messages, it uses unicast and that particular rp address should be reachable. Now, make sure that particular interface is enabled with IP pimp pass mode recommended to use loopback interface, and it should be advertised inside your IGP.
Now, once we are done with this, then I’m going to advertise as Send rp announced. And then we need to define the name of the interface. In my scenario, I’m going to use loopac zero. You must define the scope. Scope is like ttl value. And in my scenario, I don’t have more than ten routers, so I just go with ten. And the next command we need to say Send rp Discovery. We are analyzing itself as a mapping agent. And then we need to say loadbag zero and the scope. Now, we just configured these two commands here. Ipm Send rp enarms is to advertise itself as an rp and IP Send rp Discovery advertise itself as a mapping agent. Now, in my scenario, the router three is an rp as well as it is the same mapping agent as well.
Now, the next thing, if you go and verify from the router one or any router we can take. Now, here I’m going to assume that the router one is my source from where the multicast is coming for this group. And if you try to ping from the router one or any specific address, I should not get the reply. So you can see here, I’m trying to ping to that, but it’s not getting reply. But in case of static rp, it was working, but here it’s not working here. Now, the reason for this is like if you just get back to the concept, what we discussed in the Auto rp. Now, Auto rp is going to use two different multicast group addresses where the candidate rp is going to advertise itself as an rp on 224-0139 information, and the mapping agent is going to listen on this multicaster address.
And then the mapping agent is going to advertise this information to the rest of the domain on 2240 140 address. Now, before they actually learn about the rp, they should now the routers has to learn how to learn these address messages. Now, if you just verify on the router one, any of these routers, let’s go to any one of these routers. If I go to router one, if I use show Ipm route. Now, in the multicast routing table here. Now, these routers on the router two. Now, if I check on the router one. Now, the router one do not have information on how to reach there is no eskoma genres for these two multicast addresses used by Auto rp. Now, the first thing, if they want to receive the multicast traffic, if they want to register with rp, they should know how to reach the rp.
That’s the first step. Now, here in my scenario, the routers do not know how to know how to reach this multicaster. Now, here, it is like the routers cannot join to the Auto rp groups without knowing the rp, because they don’t know how to reach the rp, and they will not come to know about the rp without joining this group. It’s like recursive loop, where the routers has to join to these addresses in order to listen to the information of the mapping agent. But again, at the same time, that information is provided by rp. So to fix this kind of things, because by default, if you’re running a sparse mode router cannot join to this group that’s a mapping agent. Now, we need to fix this one in order to make this possible. There are multiple possible solutions. Now, we can either go with running a spin sparse dense mode.
Now, in the case of sparse dance mode, it’s going to work something like it’s going to run the dense mode for all the groups where there is no rp configured, and it is going to use a sparse mode for all the groups. Wherever we have an rp. Now, probably that is something you can go ahead with configuring instead of using just a sparse mode. You can simply go with sparse dense mode, or we can manually configure an rp. We can assign a static rp for only all the routers for this two multicasters so that they can listen to that multicasters and they can figure out the actual rp for the multicast group. Now, probably that is something not recommended again, because we need to go to each and every router to define the rp for this multicast group. And that’s something not recommended.
Now, we can either go with sparse genes mode, or we can define a static rp for these two multicast addresses used by Auto rp, or we can simply go to each and every router and we can configure something called Auto Rpener. Now, the advantage of Auto rp is it is going to use whenever you configure on all the routers with Auto rp listener. That’s one extra configuration we need to add. Now, what it is going to do is, it’s going to use the dense mode automatically for 239 for these two addresses, 2390, 140 and 39 for all the remaining groups, it’s going to use pass mode. It’s going to use pass mode for all the remaining groups. Now, the major difference between the major difference between the Auto arp listener and the Pim sparse dense mode is now in case of spin, sparse dense mode.
If the rp goes away. Now, if the rp goes down, then it is going to fall back to the dense mode. If there is an rp, then it’s going to use a sparse mode. Now, if you’re using Auto rp listener, then if the candidate rp goes down, so let’s say the candidate rp goes down, in that case, it will not fall back to the dense fold. That’s the major difference between these two. Now, probably in this section, I’m going to configure the Auto Rplison on all the routers. So either we can go with this static rp enhancement for this group, that’s something you’ll find in the workbook. I have documented that as well. But right now in my lab, in order to learn about that Montecas group information, I’m going to configure on all the routers. I have to say IPP Auto rp is not.
So, you can always use cushion mark to find allow the auto rp packets across the sparse mode interfaces. And the same thing we need to configure on all the routers same command on the router two as well, ipm auto archener. So let me copy paste the same command on all the routers, on the router three and on the router four, and then on the router five. Now, let’s go and verify the same. Now, if I go show ipim rp mappings, now the router one should learn about the rp information. That’s what I should see, because all the routers should learn about the rp information once we configure this, I can see Router Three is learning about the rp information here and erected via Auto rp. And let’s check on the Router One as well.
Now I can see the Router one knows about the arp information. Now, once Router One learns about the arp information if I try to generate the traffic for 224 five, let me repeat multiple times, I should get the reply here you can see the reply is coming from five five two. And if you verify on the Router one if I use Show Ipm route, you can see here on the Router One, it has an information about 2240 140 on the rp. And then if you verify here, the Router One is sending the multicaster. You can see the S comma G entries here. Let’s go to router three on the Router three. If I use your Ipm route 224 five four five I can see the entries for S comma where we are generating the traffic from Router One.
And these are the three interfaces of the Router One here. Now, you can see here it’s working fine. Now, there are three possible solutions if you want the Auto rp to work. And one thing we need to one of the major drawback with the Auto rp is they must register. Then all the routers must listen to this multicast address. Now, they should know how to reach these multicast addresses in order listen to the Auto rp messages. Now, if they don’t listen and to fix this one either, we can configure any one of these options. We can either go with pim’s pass mode or we can configure a static rp assignment for those multicasters. And we can also use some Auto rp is an option as well.
