803 BGP summarization using As set Example 2

[Music] now in this section we'll try to understand the asset option used with aggregate command with some other example so in this example what i did is i just added one router and i continued the previous configuration similar one like router 1 router 2 router 3.4 was pre-configured just like it's the same thing what we did in the previous example only the thing i added is i connected one router phi here which will be in the as 500 and then i am going to add some loop back interfaces here so router 2 is having some low back interfaces which are which is already pre-configured here and router 4 also i'm going to add the similar kind of loop back interfaces like here i'll be adding 12.0.10.1 11.12.13.1 and then once we configure this what i'm going to do is i'm going to advertise them in the bgp now this 12 dot network here will be advised in bgp and it goes to router 2 and router 2 also advertise this to a lot network to bgp which means again they get advertised to router 1. now what i'm going to do is on the router 1 we are going to summarize this 12 dot network let's say we are going to summarize these two networks coming from here as well as coming from here on router 1 and we will verify on the router phi because now we as if you remember we discussed that bgp air set whenever you configure bgp aggregation on router on as number which other than es number where the routes are originating now it's going to destroy the s path information so by default as path information will be removed and iso is set option so a set option can override this behavior so it's going to preserve that as path information let us see how it is going to preserve in this example now the only difference between the previous example in this example is we are just having some similar network the same net networks belong the subnets belong to the same network that is 12 dot network we have on the router 4 as well as on the rafter 3. so let us get to the lab here so the first thing i will do is i i already have a router 5 connected so i'll go router 5 and i'm going to configure the bgp on the router file just enable command 10.1.1.1 which is router 1 and the remote s is 100 and i don't have any networks so probably i'll i'll skip that advancements here if you want you can advance the ten dot network also now on the router one again we are going to configure router one to find neighborship neighbor 10.1.1. fire and then remote is 500 so it is ip address of router file let me quickly check what are the configurations we need to do so exactly the same configurations on the router one we configured a neighbor command pointing to router file and on the router five we configured the neighbor commander pointing to router one and then i'll also advertise network on the router file okay done so now once i configure this i should see the neighborship come up between router 5 and router 1 and i'm able to see all the routes show ipbgp i can see the 13 network which are summarized in our first example on the router 3 and then we summarize on the router 2 we 14 summarize network by verifying the asset option and it preserves the information here now the similar kind of example we are going to see but this time we have the subnets present in different different autonomous system like i have some part of subnets present in as200 which belongs to 12 dot network and some part of networks here in as400 so we'll try to understand how it is going to preserve that as path information in this example so on the router 2 i'm going to advise this to a lot network right now they are not advertised you can see on the router too i have those loopback interfaces pre-configured and i am going to advertise this loopback interfaces on the router too so router bgp 200 advertising 12.000 with slash 24 mask and then realizing the other loopbacks so i just realized all the four loopback interfaces so now if i verify show ippgp i should see those four low back interfaces 12.0123 advertised in pgp and then router one on the router one also i should see those low packs 12.01 okay now you can see i'm able to see 12.0.1.0123 so let's go to router 4 and advance this loopback interfaces so on the router 4. i think i don't have those loopback interfaces so i'll try to quickly configure those low back interfaces here so i just created this loopback interfaces on the router 4. so if you verify schweip interface brief i can see 14 is already present so i just created this 12 dot networks so my main intention is here to ensure that i'm going i am having 12 dot network some networks coming from here which is 12.0 12.0.10 11 12 13 and some part of networks coming from as200 now finally when these routes go from here router 1 is going to summarize and when it goes to router 5 will will try to preserve the as path information so in this example when compared to the previous example the only difference is now in the previous example we have all the routes originating from the same is all the subnets which are summarized now in this example we have subnets summarized from different days so let's go to router one and verify all the tool door network show ippgp include all 12s sorry identized on the router 4 in bgp so i'll advertise them in bgp router bgp 400 network 12.0.10.1 10.0 with slash 24 7 mass these are the ip addresses and then 10 12.0.11 [Music] 12 and 13. so once we configure them if you verify the router 2 let's verify the router 1 show ippgp ibbgp include 12 now you can see a router 1 is able to receive the routes coming from router 2 is 100 is 200 and these four loopbacks are coming from as400 originating from 400 and then going to 300 and 200 and finally reaching 2.01 so my requirement is to on the router one that router one has to summarize and it when it sends router 5 all these four all these eight loop packs so after summarization now here i got first network the least possible network is 12.00 and the highest possible network is 13 1 so if i summarize somewhere around let's say if i give slash 20 is a summary mask so i'll go to router 1 and then router bgp 100 and we are going to say aggregate address 12.000 with a mask of slash 20 two five five two five five two forty dot zero and then i'm going to say summary only and the reason summary only is if you don't define this option it is it is not going to suppress the individual prefixes so that is mandatory and i'm not going to use the asset option so if i don't do use a set option what happens you already know that what happens when i don't use this by default the bgp is going to advertise let me make it be more specific 12 dot okay show ippgp include 12. now it is going to advertise the summary address right it's going to advise the summary address and automatically it is going to suppress the individual specific route and the reason is we have used summary only option but it is going to remove that information is path information so it is going to simply destroy the s path information and it's going to advertise as the locally originated route and you will find this atomic aggregate attribute which is going to define that uh some information has been lost and it is done by router one so if you check on the router file the router 5 is going to receive that summary mask somewhere in network the slash 20 as it is originated from router 1 so it is coming from as100 and it's going to destroy all this path information here which i don't want so what we can do is we just need to add a set command at the time of summarization so i'll go to router 1 again and i'm going to say define the same command an option called asap so i want to preserve that as path information done so i configured the same summary command along with as set option so now if i verify once again show ippgp which include 12 now you can see this summary network even though it is locally originated but still it is going to preserve that as path information now here you can see now if you have the summary routes originating from different autonomous systems like in my example here the routes 12 networks are coming from as400 and also you are receiving the route from as to 200 which means whatever the summary mass we are using 12.0020 it is actually originating from multiple a's it's coming from 400 and also going via 300 and there are some rods belongs to 200 and it's going to preserve this complete ace path information and it is going to show in the brackets you can see here uh flower brackets so which means so the order may not be correct so it will be a random order but it's going to say that it's going to preserve that as path information in flower brackets so if you if you remember the last example which we did we we don't have these brackets mentioned over there and the reason is because uh all the summary routes are originating from the same is so if it is coming from the same as you don't see these brackets defined but whenever you see this it means that you have the summary the individual prefixes inside the summary address were actually originating from different different autonomous system numbers and moving between different a's so this one example also this example is uh one another kind of a set which is most commonly used where you may have a requirement that you are receiving the route from both the sites probably let's say you are receiving dual dot network from this side and some other set of two laptops coming from this side but when this router is going to send to other routers it's going to summarize but still this as path information will be preserved and it's going to ensure that there's no routing loops so whenever any update comes on this router again back whenever it sees its own as number inside that it will ensure that it will not install those routes the default bgp loop prevention mechanism [Music]

Channel: Sikandar Shaik

Views: 2,346

Keywords: ccna, noa, ccna videos, ccnp, noa videos, cisco, ccie, subnetting, ccna security, bgp, ospf, firewall, ccna subnetting, ipv6, bgp videos, stp, ccna vdieos, ccna free video, ccie certification, ios, iou, virtual, eigrp, cisco virtual lab, iosv, asav, gns3, routing, noa vdieos, noa solutions, zone based firewall, zone pair, zbf, flsm, cisco firewall, cisco security, cisco certifications, wan, ip addressing, netmetric, vlsm, eigrp configuration, vlan, ccna, noa, ccna videos, ccnp, noa videos, cisco

Id: IfZEDNr6CBM

Length: 12min 17sec (737 seconds)

Published: Sat Aug 08 2020