real world BGP issue

Hi;

 

I have a scenario at work, that i am trying to think through. 

 

Being a service provider network, we peer with commercial peers like google (direct peering, one hop away), L3,  akamai etc.

 

We also have peering with academic research networks. These routes are non commercial routes.

 

Our clients, when they form bgp peering with us, they receive both commercial and non commercial routes from us.

 

One of our client complained recently,  that they do not  wish to see commercial routes coming into them through us.  As we tag commercial and non commercial routes with community vlaues, we just advised them of the tag for the commercial routes and they have now taken care of the requirement by filtering our those routes (not sure if they used prefix list or changed local preference value). This happened around mid march.

 

Some of our other clients are complaining that thier link connecting them to our AS is barely busy, there is hardly any traffic traversing that link (for commercial and non commercial destinations alike). This has been on going since mid march. They have another interconnect with another service provider, and they see that link being extra busy.

 

This is becoming a reqular occurance now. Please suggest as to why it may be happening. We have not changed anything at our end. I am not sure if the client/clients have made any changes on thier side. How do I troubleshoot this issue.

 

regards

 

 

Comments

  • It's possible your clients other provider has a direct peering that is heavily used which you don't. 

    Another option could be that the other provider has a longer match to some of the large comercial peers than you do.

    I recommend getting some of the heavily utilized routes that the customers use and a list of other providers they use. You can then look up the routes in the other providers public route servers and compare them to your own.

  • Hi!

    Sounds interesting...

    I would check for the following things:

     

    1) Has a customer that is multihomed become a transit AS?

    2) Check all the BGP attributes and the BGP tables...that some interfaces are not used can only have the reason that BGP doesnt find that link attractive. This is also what jguagliata said....go to the route-servers and check whats going on.

    3) Let the customers come into play and maybe let them also check what routes with which preference etc. they are seeing.

     

    Regards!

    Markus

  • You can go through several free route-servers and check which announces you see for each complaining client.

     

    Like route-server.cerf.net, route-server.ip.att.net etc..

     

     

  • Yep this one is also a handy website to do it.

    http://routeserver.org/

     

    Regards!

     

     

  • It's possible your clients other provider has a direct peering that is heavily used which you don't. 

    Another option could be that the other provider has a longer match to some of the large comercial peers than you do.

    I recommend getting some of the heavily utilized routes that the customers use and a list of other providers they use. You can then look up the routes in the other providers public route servers and compare them to your own.

     

     

    Hi jguagliata ;

     

    thanks for the reply. 

     

    I am afraid i did not understand clearly as to what i solution can i formulate for this problem. I am sorry but i am not familiar with a route server. Can you please advise me how do these servers work and are used for.

     

    regards

     

     

  • Hi!

    Sounds interesting...

    I would check for the following things:

     

    1) Has a customer that is multihomed become a transit AS?

    2) Check all the BGP attributes and the BGP tables...that some interfaces are not used can only have the reason that BGP doesnt find that link attractive. This is also what jguagliata said....go to the route-servers and check whats going on.

    3) Let the customers come into play and maybe let them also check what routes with which preference etc. they are seeing.

     

    Regards!

    Markus

     

     

    Hi Markus;

     

    thanks for the reply.

     

    I am sorry for more ignorant questions as below:


    How must i check if a customer that is multihomed  has become a transit AS?

    If BGP does not select a certain netwok to be installed in the bgp table to reach a prefix, i would need to check the bgp attributes attached to that network. I am not sure how to check those on customers routers, provider routers and ours, can you please highlight how to do that.

    How can the customers check what preferences are attache dto teh routes. We send all types of routes (commercial and research) to our clients with community vlaues. They can have route maps etc to alter the attributes of the prefixes being received from us. I amnt sure if they are doing that. Do you think them adjusting the local preference vlaue for routes learnt from us for exmaple on thier end, would help them?

     

    Please help...

    regards

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

  • It's possible your clients other provider has a direct peering that is heavily used which you don't. 

    Another option could be that the other provider has a longer match to some of the large comercial peers than you do.

    I recommend getting some of the heavily utilized routes that the customers use and a list of other providers they use. You can then look up the routes in the other providers public route servers and compare them to your own.

     

     

    Hi jguagliata ;

     

    thanks for the reply. 

     

    I am afraid i did not understand clearly as to what i solution can i formulate for this problem. I am sorry but i am not familiar with a route server. Can you please advise me how do these servers work and are used for.

     

    regards

     

     

     

    In a nutsheel, a route server is a router/server that is sitting on the Internet that gives you the ability to view the BGP routes:

    http://www.routeviews.org/

    HTH

    Good luck!

  • I am sorry for more ignorant questions as below:

    Abolutely no problem :)

     

    How must i check if a customer that is multihomed  has become a transit AS?
    .

    This post from Ivan may help you understand what I mean.

    http://blog.ioshints.info/2008/04/bgp-essentials-non-transit-as.html 

     

     

    If BGP does not select a certain netwok to be installed in the bgp table to reach a prefix, i would need to check the bgp attributes attached to that network. I am not sure how to check those on customers routers, provider routers and ours, can you please highlight how to do that.

    If BGP does not install a route this could have certain reasons. For example...the gateway is not reachable or there is a better path or so.

    You can check packetlife for details: http://packetlife.net/blog/2008/nov/19/probable-reasons-bgp-isnt-installing-route/ 

     

    How can the customers check what preferences are attache dto teh routes. We send all types of routes (commercial and research) to our clients with community vlaues. They can have route maps etc to alter the attributes of the prefixes being received from us. I amnt sure if they are doing that. Do you think them adjusting the local preference vlaue for routes learnt from us for exmaple on thier end, would help them?

    Well adjusting localpref for example is probably a workaround but it will probably not a clean installation. If you dont have a chance to get on the customer routers and take a look, well...they can do whatever with the routing information you send them via bgp. You cannot force a router to do something just with advertising. When the customer site filters your arguments then you are stuck here. Partner troubleshooting with the customer should be on the roadmap here I think.

     

    Regards!

    HTH!

    Markus

  • peetypeety ✭✭✭

    Being a service provider network, we peer with commercial peers like google (direct peering, one hop away), L3,  akamai etc.

     

    Define "peer with" please.  Are you paying for transit (and receiving full table from those that have it), are you paying for peering (receiving only "their routes" and "their customer routes"), are you getting "settlement-free peering" (receiving only their routes and their customer routes, at no cost to either party), or are any of these networks customers of yours?

    Some of our other clients are complaining that thier link connecting them to our AS is barely busy, there is hardly any traffic traversing that link (for commercial and non commercial destinations alike). This has been on going since mid march. They have another interconnect with another service provider, and they see that link being extra busy.

    Ask them for a 'sh ip bgp x.x.x.x' for some value of x.x.x.x that's operationally significant, such as the IP address of a google.com webserver, a cnn.com webserver, etc.

    This is becoming a reqular occurance now. Please suggest as to why it may be happening. We have not changed anything at our end. I am not sure if the client/clients have made any changes on thier side. How do I troubleshoot this issue.

    I'm suspecting either poor choice of prepending, poor management of local preference, or one or more peers that have set 'no-export' on what they announce to you.

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