Hi guys . This may sound like stupid questions :) but we have what we have . We have enterprise company with sites around country and sites are connected with L3 MPLS with BGP on the customer edge routers , no any MPLS settings on customer edge routers .
1. If MPLS will down will I still get updates about networks with BGP ?
2 if yes , how can I conclude that MPLS is having problem ?
3 If no (no BGP connection) does it mean I will lose ip route 0.0.0.0 0.0.0.0 too (in case only 1 interface to ISP_and_MPLS provider) ?
I didn't had issues with MPLS links yet so would be useful to know and be ready :)
Thank you .
From a customer perspective it is best to think of it as just a normal WAN connection ie. you do not need to be concerned with the MPLS part of it.
That said what does matter is what type of connectivity is being provided with MPLS and what exactly you mean by MPLS being down.
So lets assume you have any to any connectivity between your sites meaning each site can go direct to any other site rather than via a central site.
If the PE device (owned by the SP) that a CE device connects to at one of your sites fails then you will no longer receive BGP routes for remote sites nor will you be able to advertise your local site routes to the remote sites.
That means the site can no longer communicate with any of your other sites and they cannot communicate with your local site.
If all the other sites connect to different PEs though ie. not the PE that has failed, the other sites will still be able to communicate with each other.
The above is just an example as there can be many different types of failure within the MPLS clould so it's impossible to cover all scenarios.
"If all the other sites connect to different PEs though ie. not the PE that has failed, the other sites will still be able to communicate with each other." I got confused a little bit :
How other sites can be connected to different PE , I thought I must have the same MPLS provider on both sides of the mpls connection ?
Sorry I should have explained it a little better.
An MPLS network is made up of P and PE routers and the ones you connect to are PE routers.
These are owned and maintained by the SP themselves.
An SP will have multiple PEs spread geographically for connections to customers.
So your CE routers connect to these PEs but all your sites don't connect to the same physical PE router because they are in different places.
A failure of a PE device will only affect the CEs connected to that PE is what I was trying to say.
Does that make more sense ?
If not by all means come back.
ok, I got it . If I have MPLS cloud between sites A B C D (on L3MPLS it will be full mesh ) and PE connected to site A is having problem , B C D will still have routes to each other via BGP . On site A I can check if I will not have BGP neighbors and route to B C D so it's MPLS issues . At this case Is it possible that I will still have Internet access on site A ?
Not if your internet access is via MPLS PE/CE router that fails, however if you have a separate physical connection for internet access then its is possible you could obtain access to the internet.
Depends on what outage your experiencing.
In case if I don't have a separate redundant ISP circuit . I thought MPLS it's like pipe/tunnel , for example I may have ipsec down but Internet will be still up :) . So u mean I will lose internet too, so it works differently . Right , I will have all updates with BGP and then redistributed to my IGP so if I lose MPLS/BGP I will lose route to outside too , correct?
It doesn't work differently.
All Paul is saying is that if the internet connectivity is not at the site that loses it's connection to the PE or the PE is down you won't have internet connectivity.
Like I say just think of the MPLS network as a WAN ie. if your site goes across the WAN to get to other sites and also one of the other sites also has the main internet connection then you can't connect to either.
Think of the mpls provider network as a engine and the spoke sites are cogs attached to this engine via gears.
Now if the engine fails then ALL cogs (sites) will NOT be able to comunicate with each other
However if a specific gear connecting to a specific cog (site) breaks then that cog (site) won't be able to communicate to the engine or other cogs.(sites)