Hi there. I'm having a problem with the setup pictured. In AS 3, all of the routers are able to ping the routers in AS 89 and AS 140. However, the routers in AS 89 and AS 140 cannot ping past R1 and R5 respectively. Each router has a route to the destination in its routing table, all OSPF areas are configured as standard, and there are no routing loops that I can see. R1 and R5 are redistributing OSPF internal and external 2 routes to their BGP partners. R1 is an eBGP neighbor to R6 and R5 is an eBGP neighbor to R8.
I've included the routing tables of all the routers along the transit line. Here is the output of show ip route 192.168.10.1 on R6
R6#show ip route 192.168.10.1
Routing entry for 192.168.10.0/24
Known via "bgp 89", distance 20, metric 0
Tag 3, type external
Redistributing via ospf 1
Advertised by ospf 1 subnets
Last update from 100.100.100.1 00:20:44 ago
Routing Descriptor Blocks:
* 100.100.100.1, from 100.100.100.1, 00:20:44 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 3
Okay, so I found a workaround. Turns out that redistributing BGP routes into an IGP is, in technical terms, stupid. Rather just do a full iBGP mesh. I still have no idea why this setup doesn't work though.
So if you try to ping from R6 past R1, the pings probably fail since it is probably using the 100.100.100.2 as the source. If you source ping from R6 using 22.214.171.124 as source it will probably succeed.
The same holds true for R8 and it using the 126.96.36.199 as the source.
Hope this makes sense and helps.