Hi,
I don't fully agree with the provided solution for task 4.2
In task we have R6 which is dual-homed CE to R4 PE and R1 PE. Integrated IS-IS is used for PE-CE protocol. IS-IS is redistributed to MP-iBGP and vice versa.
The classical problem is that by default IS-IS has an AD=115, and iBGP has an AD=200, so we should change AD for IS-IS to be bigger than 200 which is done in the solution and everything looks fine.
But lets see what will happen with a prefix "A" (for example R5 lo1) if we clear on R1 the MP-iBGP to the RR (in this case R4).
R6 will know for prefix "A" via ISIS from R4, then R6 will advertise this LSA to R1.
R1 will receive prefix "A" via ISIS from R6 and will install it with AD201 (bigger than 200), then it will redistribute this "A" into MP-iBGP and this route should appear as locally advertised "sourced" which will be more preffered that the same prefix "A" from R4. So even that AD is 201(>200) prefix A will be in routing table of R1 known from ISIS.
We should use route tags to be sure that route is not routed via R6, or we can change BGP WEIGHT attribute on R1 for routes coming from R4 (via MP-iBGP)