BGP Attribute MED

That's correct. In this lab however Suriname doesn't use Haiti anymore but when it does you need to make sure the next hop is resolvable.

Good question. The same thing applies here...router Cuba will have to know about the link between Haiti and Jamaica. Router Haiti will have to know about the link between Cuba and Jamaica.

You can either advertise those links in a routing protocol or you can use the BGP next-hop-self command. If you use next-hop-self Haiti and Cuba will advertise themselves as the next-hop and not router Jamaica.

That's strange...even when you reset the BGP neighbors? Check if router Haiti and Cuba both have learned network 4.4.4.0/24 through EBGP and that they have a working IBGP adjacency with router Suriname. They should advertise this network through IBGP.

I simply cannot understand this behavior.

This is debugs from Suriname:

Quote:

Suriname#
*Mar 1 0015.555: BGP(0): 192.168.12.2 rcvd UPDATE w/ attr: nexthop 192.168.12.2, origin i, localpref 100, metric 200, path 2
*Mar 1 0015.559: BGP(0): 192.168.12.2 rcvd 4.4.4.0/24
*Mar 1 001:11.715: BGP(0): Revise route installing 1 of 1 routes for 4.4.4.0/24 -> 192.168.12.2(main) to main IP table
*Mar 1 001:11.735: BGP(0): 192.168.13.3 rcvd UPDATE w/ attr: nexthop 192.168.13.3, origin i, localpref 100, metric 100, path 2
*Mar 1 001:11.735: BGP(0): 192.168.13.3 rcvd 4.4.4.0/24
*Mar 1 001:11.735: BGP(0): Revise route installing 1 of 1 routes for 4.4.4.0/24 -> 192.168.13.3(main) to main IP table
*Mar 1 001:11.735: BGP(0): updgrp 1 - 192.168.12.2 updates replicated for neighbors: 192.168.13.3
*Mar 1 001:11.735: BGP(0): updgrp 1 - 192.168.12.2 updates replicated for neighbors: 192.168.13.3
*Mar 1 001:11.747: BGP(0): 192.168.12.2 rcv UPDATE about 4.4.4.0/24 -- withdrawn

Why on earth is the route to 4.4.4.0/24 via 192.168.12.2 (metric 200) 'withdrawn' ? - it makes perfectly sense that it's not present in the routning table - but why is it not present in the BGP table ?!? :'(

Question And this admittedly goes beyond lab - Suriname should also use the route via Cuba right, so the next-hop-self (for neighbour Suriname) is required on both Cuba and Haiti right ?

But what about the neighbor relationship between Cuba and Haiti - should they be configured as next-hop-self aswell (if not - their routes to AS2 will be invalid without an IGP underneath) ?

If I configure Haiti and Cuba as next-hop-self (IE they both announce themselves as the next-hop to each other) - Router Suriname will only get ONE bgp path/route to 4.4.4.0/24 - the one through Cuba (why is that ?!)

I just loaded my final configuration and set "next-hop-self" for Cuba and Haiti. This is what happens:

Router Haiti can get to network 4.4.4.0 through Cuba or Jamaica. You can see this in the BGP table. It installs the route through Cuba because of the MED.

Router Cuba uses the direct link to get to network 4.4.4.0 through Jamaica.

BGP will only advertise the best path. Router Haiti only advertises network 4.4.4.0 with next hop 3.3.3.3. So does router Cuba.

Router Suriname will end up with a single entry for network 4.4.4.0 / 24 in its routing table.

Thanks alot for the feedback Rene (and for another great lab)