Task 2.10 BGP Aggregate

We need to advetise the loopbacks if we are to advertise "all internal networks" to our EBGP neighbors as aggregates.

the SG does not show that we also need to do the same thing from R2 to R4, ie; not send the aggregate (filter it out) to out external neighbors.

or is it "assumed" that AS100 and AS200 are 2 seperate Administrative Domains and we have dont have to worry about sending them the aggregate between them.

but this does not make any sense as we are "not" sending the aggreate from Sw2 to Sw1.

hope that this makes sense.

 

Comments

  • You'll find that the INE labs reflect the CCIE lab exam itself, which always refers to your devices as your internal network.  This is slightly counterintuitive, since we clearly have two separate AS domains, but that's how it goes.  So when they say not to advertise the aggregate internally, they mean that R4/R2 shouldn't be sending each other the aggregate.  External = BB routers.

     

    In the same way, your entire internal space consists of the IP addresses throughout all your devices, regardless of AS.  Hence the SG creating an aggregate for 129.X.0.0/16.

     

    This is a couple months late, but figured I'd answer it in case someone else comes to the forums looking for the same thing.  I'm guessing you've gotten this all straightened out by now :)

    Jeff 

  • I am using v5.10.018 version.  I agreed with you we need to advertise the loopbacks into BGP process, if not edge router (SW2, R2, R6) won't able to aggregate the route to BB routers, for example 150.1.0.0/16 subnet. 

  • Yeah I added a route map on SW2, R6 and R2 to prevent those specific loops back going to AS 54 & AS 254 respectively as well.

     

    Cheers

    Inder Vaid

  • I advertised the loopbacks of each router connecting to the BBs and used the summary-only keyword for the loopback summary.  This way the BBs would actually have reachability to the 150.1.0.0/20 space. Then I used a route-map to each neighbor internal to the network denying the loopbacks summary prefix.

    Anyone have comments on this approach?

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