Reachibility BGP received route

[Jaro]

Hello, 

I have 2 ISPs,  one primary and one secondary.

I have two routers on my site and both have BGP with different ISPs, and between them, there is iBGP.

ISP1                ISP2

 |                       |

BGP                 BGP

 |                       |

R1---IBGP--- R2

I want to set up IP SLA let´s say to ip 8.8.8.8 (to test reachibility to the Internet)

If I had two static routes, it is okay because I would set it up like this:

R1(config)# ip route 0.0.0.0 0.0.0.0 2.2.2.2 track 1
R1(config)# ip route 0.0.0.0 0.0.0.0 3.3.3.3 10

But problem is that,I get default routes from ISP through BGP, so question is how to set it up ?

Thank you

[paul driver]

Hello

If you receiving default from both isps then you don't need to use static routes or ip sla to perform failover you can use the Local preference bgp path attribute to do this when both defauts are being advertised to your routers

rt1
router bgp 1

neighbor 1.1.1.2 remote-as 2
neighbor 1.1.1.2 next-hop-self

bgp default local-preference 400000

[Jaro]

Hello Paul, 

Problem is, that if one of ISPs will have issue behind router, where is bgp configured, my router will still sending packets via my primary provider, because of this problem I want to set up IP sla to 8.8.8.8, and local pref, will not help me.

Correct me if I´m wrong.

Thank you

[Dennis Mink]

lets say router R1 is your primary ISP. if you drop the connection to your ISP, it will no longer receive a default route from that ISP but will have a default route thru iBGP from R2, so it will pass the traffic on to R2 and out ISP2 as far as i can see.

[Jaro]

Hello Denis,

Yes you are right, if I drop connection between R1 and ISP1, I will no longer receive default route, BUT problem is if this connection will be without issue and problem will be behind ISP1 in direction to the Internet, then I will receive default route but I will not have any connectivity because traffic will go via ISP1 (because of Provider issues behind ISP router).

So, what I need is to switch traffic via ISP2 in case of any issues with ISP1, and I guess only way how to do it is by IP SLAs.

Correct me if I´m wrong.

Thank you

[paul driver]

Hello

your statics will overide the defaults coming from your isps so if want to use your own default static then this is applicable 

ip sla 1

icmp-echo 8.8.8.8 2.2.2.1

ip sla scheduled 1 start now life forever

track 1 rtr 1 reachability 

ip route 0.0.0.0 0.0.0.0 2.2.2.2 track 1
ip route 0.0.0.0 0.0.0.0 3.3.3.3 2

[Jaro]

Hello,

Could you please help me ? I still didn´t have a solution.

I found out, that I can do it by filtering bgp advertisments routes, but I´m not sure if it is correct solution. 

Thank you