hello guys
this topic is little bit interesting, if you are sincerely looking for the help to understand THE " bgp conditional advertisement." types.
1. advertise-map with exist-map
2. advertise-map with non-exist-ma
BIG QUESTION...
why we need bgp conditional advertisement???
MY SUGGESTION.
suppose your company is multi-homed with different ISP's. let say, for the backup or redundant purpose, your company is connected to two ISP named ISP X and ISP Y. ISP X is much slower link ( T1 link).
as a network administrator what you want is all traffic should follow ISP Y link as its much faster.
to fulfill these dreams, you need to play with your internet facing router and do some interesting things with it...
you can fulfill these dream by two methods.
1. advertise-map with exist-map or
2. advertise-map with non-exist-map
Note*
a > 192.168.0.0/24 is your company LAN address
b> 10.10.12.0/24 is WAN address between R1 and R2( your router to ISP X or LINK A)
c> 10.10.13.0/24 is WAN address between R1 and R3( your router to ISP Y or LINK B)
SCENARIO 1
LINK A is connection from ISP X and is much slower link, what you want is as long as LINK B is exist or up, traffic should follow LINK B ( through ISP Y), or you never want traffic should follow LINK A. if LINK B goes down then traffic should automatically follow LINK A..
what we are going to do here is
> let say,ISP Y advertising prefix 30.30.30.0/24 to you, as long as this prefix is in your router's RIB, you are not going to switch incoming traffic through LINK A.
>once LINK B goes down and this prefix is removed from your router's RIB, then you are going to switch incoming traffic through LINK A.
BASIC eBGP PEERING AND CREATING REACHEBLITY.
R1 config.
R2 config.
NEXT POST i am going to write about ADVERTISE_MAP with EXIST_MAP
this topic is little bit interesting, if you are sincerely looking for the help to understand THE " bgp conditional advertisement." types.
1. advertise-map with exist-map
2. advertise-map with non-exist-ma
BIG QUESTION...
why we need bgp conditional advertisement???
MY SUGGESTION.
suppose your company is multi-homed with different ISP's. let say, for the backup or redundant purpose, your company is connected to two ISP named ISP X and ISP Y. ISP X is much slower link ( T1 link).
as a network administrator what you want is all traffic should follow ISP Y link as its much faster.
to fulfill these dreams, you need to play with your internet facing router and do some interesting things with it...
you can fulfill these dream by two methods.
1. advertise-map with exist-map or
2. advertise-map with non-exist-map
TASK1
IN this section we are going to discuss about advertise-map with non-exist-map. HOW THEY WORK TOGETHER.
let begin.. following is our scenario.
a > 192.168.0.0/24 is your company LAN address
b> 10.10.12.0/24 is WAN address between R1 and R2( your router to ISP X or LINK A)
c> 10.10.13.0/24 is WAN address between R1 and R3( your router to ISP Y or LINK B)
SCENARIO 1
LINK A is connection from ISP X and is much slower link, what you want is as long as LINK B is exist or up, traffic should follow LINK B ( through ISP Y), or you never want traffic should follow LINK A. if LINK B goes down then traffic should automatically follow LINK A..
what we are going to do here is
> let say,ISP Y advertising prefix 30.30.30.0/24 to you, as long as this prefix is in your router's RIB, you are not going to switch incoming traffic through LINK A.
>once LINK B goes down and this prefix is removed from your router's RIB, then you are going to switch incoming traffic through LINK A.
BASIC eBGP PEERING AND CREATING REACHEBLITY.
R1 config.
R2 config.
R3 config.
we have completed basic peering configurations.
ON R1, we will configure following prefix-list and route-maps.
you might be confused why i used community-list here,, good reason is, i just wanted to track whether prefix 30.30.30.0/24 is come from ISP Y. or R3 or not.
if this prefix is truly come from R3, prefix is set with community 300:100.
as i configure all incoming prefixes from ISP Y should be set community value 300:100,
i just confirmed below.
VERIFICATION.
1. Before LINK B is down.
Prefix 30.30.30.0/24 is R1 routing table.
HENCE :: R1 is not advertising prefix 192.168.0.0/24 to R2. check below,
2. After LINK B goes down.
I just simulated that prefix 30.30.30.0/24 is stop advertise in bgp in R3.
Now Prefix 30.30.30.0/24 is removed from R1 routing table.
3. now R1 is advertising prefix 192.168.0.0/24 into LINK A or R2.
or
Thanks guys..
NEXT POST i am going to write about ADVERTISE_MAP with EXIST_MAP
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