BGP / IGP
I just did this lab twice.
First time, I was breezing through everything till I started the BGP section then I figured out I was loosing some connectivity to the 30 networks. Things seemed too messed up for me so I killed all config and started from scratch.
Second time, I found problems in 4.13, which there was no mentioned of mutual redis on R4 between RIP/OSPF. I peeked into the SG and there is a line of redis OSPF into RIP.
I then moved on to do BGP only to find out there is also a hidden area 54 at BB3 (which should not involved in BGP in this lab, but they are linked between the two BBs). I couldn't ping the 28 network so I went into the BB routers and confirmed the 28 networks are originated from BB3 to BB1 (which should have nothing to do with BGP at all), then in turn advertised into R6. BB1 and BB3 have their BGP routes but they can't ping each other. Now after I redis OSPF back into RIP on R4, BB3 learned about the 112-119 networks. Pinging from R1 to these network will sometime take the path to BB1 (works) and sometimes to BB3 (won't work). So, I think there is a big mess out there.
I don't know what to do if I see this in real lab. Here I can peek into the BBs to confirm my suspections. But during the real lab, you can't get into the BBs so there are going to be lots of guessing works. Or I might have to over config with filters to really stop things from getting nasty.
I'm done with it but I wish this lab were written better. [:(]