How work Full View and Default and what is difference between them

[Mlex1]

router bgp 100
bgp log-neighbor-changes
neighbor 192.168.1.1 remote-as 200
neighbor 192.168.1.1 des R1
neighbor 192.168.1.1 default-originate
!
R1
ip prefix-list DEFAULT seq 5 permit 0.0.0.0/0
!
route-map RM_DEFAULT permit 10
match ip address prefix-list DEFAULT
!
router bgp 200
template peer-policy TEST
route-map RM_R03_OUT out
default-originate route-map RM_DEFAULT
soft-reconfiguration inbound
send-community both
exit-peer-policy
neighbor 10.10.10.2 remote-as 300
neighbor 10.10.10.2 description R03
neighbor 192.168.1.2 remote-as 100
neighbor 192.168.1.2 description R1
!
address-family ipv4
neighbor 10.10.10.2 activate
neighbor 10.10.10.2 inherit peer-policy TEST
neighbor 192.168.1.2 activate
exit-address-family
!
Here my question is there any port config so that they answer whih port of config default and which port for full view ?
as i see default-originate route-map RM_DEFAULT config no need, why i thing so?
1. I advertise default ot R3 here all network, via prefix-list and route-map.

2. default-originate route-map RM_DEFAULT make default route but not add on bgp table 0.0.0.0/0, emulate default route also this advertise to R3, here i confuse and could't understand

also read here 

https://community.cisco.com/t5/routing/difference-between-receiving-full-updates-and-a-default-route/td-p/3836482

[Harold Ritter]

Hi @Mlex1 ,

The difference between receiving only the default route or the full routing table (full view) is that you get a lot more granularity in your routing decision if you receive the full view. If you only have one ISP, it does really matter as this is the path you can take. But if you have mutiple service providers, receiving the full view allows a better egress traffic distribution between the multiple ISPs than if you only received the default route from each one of them.

> 1. I advertise default ot R3 here all network, via prefix-list and route-map.

If you only want the default route to be advertised to R3, you need to apply the route-map in the following way 

router bgp 200

address-family ipv4

no neighbor 10.10.10.2 inherit peer-policy TEST

neighbor 10.10.10.2 route-map RM_DEFAULT out

> 2. default-originate route-map RM_DEFAULT make default route but not add on bgp table 0.0.0.0/0, emulate default route also this > advertise to R3, here i confuse and could't understand

It is normal behavior for the default-originate to advertise the default route to the neighbor without the default being present in the BGP table. 

As I mentioned in the other post, you do not need to use the dafault-originate on R2, since you already received the default route from R1. The default route received from R1 will propagate from R2 to R3.

[Mlex1]

> As I mentioned in the other post, you do not need to use the dafault-originate on R2, since you already received the default route from R1. 

What if, for example, I receive a full Internet routing table from my ISP, but I don’t want to advertise the full view to a specific BGP neighbor?
As we both know, the full table consumes more memory and CPU.

In this case, how can I advertise only a default route (0.0.0.0/0) to that particular neighbor?

Am i right this command default-originate route-map RM_DEFAULT 

[Harold Ritter · Accepted solution]

Hi @Mlex1 ,

As I mentioned in my previous post, you do not need the "default-originate" command at all on R2. The default route you send to R3 is the one that you receive from R1 (ISP simulation). The route-map RM-DEFAULT is used to send the default route and reject everything else. It needs to be applied towards R3, as follow:

neighbor 10.10.10.2 route-map RM_DEFAULT out

[Mlex1]

yes i understood, i done a test lab on eve-ng afterward everything clear for me 

[M02@rt37]

Hello @Mlex1 

There is no 'port' distinction for default versus full view. It is purely based on BGP policy and what routes are exchanged...