How do BRs check performance of different ways in PFR Solution?

[msmoon]

Hello!

I have some question about BR's activity.

If there is a router which acts as MC/BR, and then it connected with two ISP(ISP_A, ISP_B).

MC/BR router should check both way to a server which is serving video, for example.

Bytheway, If the video server is connected with two ISPs then, the server-side router should choose a way to MC/BR router.

if I want to check only with ICMP echo, so setup BR to check ICMP echo through two way(using client-side interface as a source).

but returning echo-reply always come through the best way to MC/BR router.

I mean how BR can check the returning path?

what am I supposed to do?

or did I understand wrong?

[Marwan ALshawi · Accepted solution]

Hi there

This is a very good and valid question, to answer this let's assume that each ISP link has ip address allocated by the ISP to you and this ip you do not need it other than to establish the routing peering with the ISP PE in other words you do not necessarily need to advertise this ip, so if you source your probe from the external interface of ISP1 going to external interface of the branch of ISP1 link and you can avoid advertise those links and just use for example a static route for that ip point to ISP1 this way you will make sure the probe will take one way/path this has to be done on both sides per ISP/link

Hope this help

[msmoon]

Thanks for your answer..

Bytheway, these days we are in problem in lack of IPv4 addresses pool.

So, in many cases ISP gave us private ip address for peering between ISPs and our routers.

then is there any solution for that instead of getting public ip addresses for peering form ISPs?

[Marwan ALshawi]

Let's put it this way

Site1-----192.168.1.0/30----ISP1----172.16.1.0/30----site2

If you do not advertise the links to the ISP in your routing and in site one you put static route for 172.16.1.0/30 point to ISP1 next hop and in site2you do idea then the only path for traffic sourced and distened between these addreses will over ISP1

Hop this help

[msmoon]

Yes, you right..

But that case is only happen when two sites use same ISP.

If they are connected through sevral ISPs then....  (T.T) ..

      FYI,   Site1 ----------192.168.1.0/30--------ISP1---------192.168.2.0/30-----ISP2-----172.16.1.0/30------Site2

You meant, I should find a way to make packets send&receive through same path, right?

and there is no surprising solution for this, right?

[Marwan ALshawi · Accepted solution]

Well the ISP will Learn this route via the other ISPs otherwise you won't get connectivity I am talking about the ISP link ip

But in anyway you can still control it by making sure the source and distention ip of the probe is not being advertised to other routers on you routed network and enforce it to use the desired path you might use specific loopback interfaces for those probes

But again as i said this is very good point if someone overlooked it then the result won't reflect the actual situation of the path

. 

Hope this help

[msmoon]

Thanks for your attention.

When I saw documents on cisco about PFR, it said like everything is possible, I felt.

Anyway, thanks again.