Problem 1
----------
a)
AS 1:
------
1.2.3.0/24		internal
17.9.8.0./25	internal
5.2.0.0./16		via AS 2
92.18.2.0/24	via AS 3
18.2.1.0/26		via AS 4, AS 2
80.90.42.0/24	via AS 5, AS 3
15.23.2.0/24	via AS 6, AS 3

AS 2
------
1.2.3.0/24		via AS 1
17.9.8.0./25	via AS 1
5.2.0.0./16		internal
92.18.2.0/24	via AS 3
18.2.1.0/26		via AS 4
80.90.42.0/24	via AS 5, AS 4
15.23.2.0/24	via AS 6, AS 4

AS 3
------
1.2.3.0/24		via AS 1
17.9.8.0./25	via AS 1
5.2.0.0./16		via AS 2
92.18.2.0/24	internal
18.2.1.0/26		via AS 4
80.90.42.0/24	via AS 5, AS 6
15.23.2.0/24	via AS 6

AS 4
------
1.2.3.0/24		via AS 1, AS 2
17.9.8.0./25	via AS 1, AS 2
5.2.0.0./16		via AS 2
92.18.2.0/24	via AS 3
18.2.1.0/26		internal
80.90.42.0/24	via AS 5
15.23.2.0/24	via AS 6

AS 5
------
1.2.3.0/24		via AS 1, AS 2, AS 4
17.9.8.0./25	via AS 1, AS 2, AS 4
5.2.0.0./16		via AS 2, AS 4
92.18.2.0/24	via AS 3, AS 6
18.2.1.0/26		via AS 4
80.90.42.0/24	internal
15.23.2.0/24	via AS 6

AS 6
------
1.2.3.0/24		via AS 1, AS 3
17.9.8.0./25	via AS 1, AS 3
5.2.0.0./16		via AS 2, AS 3
92.18.2.0/24	via AS 3
18.2.1.0/26		via AS 4
80.90.42.0/24	via AS 5
15.23.2.0/24	internal


b)
AS 5 announces 1.2.3.0/24, what leads to AS 4 and AS 6 writing it in their BGP tables (see below) AS 1 - 3 are not affected because they have have shorter paths from the announcment of AS 1. This assumes that RPKI/ROAis not in place.

AS 4 after attack
------
1.2.3.0/24		via AS 5
17.9.8.0./25	via AS 1, AS 2
5.2.0.0./16		via AS 2
92.18.2.0/24	via AS 3
18.2.1.0/26		internal
80.90.42.0/24	via AS 5
15.23.2.0/24	via AS 6

AS 6 after attack
------
1.2.3.0/24		via AS 5
17.9.8.0./25	via AS 1, AS 3
5.2.0.0./16		via AS 2, AS 3
92.18.2.0/24	via AS 3
18.2.1.0/26		via AS 4
80.90.42.0/24	via AS 5
15.23.2.0/24	internal