Re:EIGRP faster convergence.
I believe what's being described is a "Feasible Successor", which, I recall (?) requires it meet certain conditions. I.e. I believe an alternative route has to sometimes be calculated.
That said, having an alternate route to install would decrease network interruption time.
On modern platforms, OSPF can often pretty quickly calculate an alternative.
BTW, with OSPF, if I'm really concerned about the time it takes to calculate another route, I might design the network's alternate path as ECMP, then OSPF needs not to calculate the alternator path. Of course, ECMP will use both paths, so they should be similar in performance.
Or determine if "OSPF Loop-Free Alternate (LFA) Fast Reroute (FRR)" is supported.
Re: IS-IS
Indeed often used in carrier networks, but perhaps that's has more to do with it being "extensible" because of it using TLVs. Carrier equipment often will support it.
Also BTW, besides being like OSPF link-state, it also can use a two layer area design.
Personally, having used both OSPF and IS-IS in a national Enterprise network supporting 100,000 users, didn't find IS-IS superior for typical Enterprise usage.
Re: RIP
OP notes actually RIPv2 is being used, so not just classful routing like original RIP. However comments about RIPv2 network statements are correct! (Personally, first time tried using RIPv2, and found these "features", I passed on using it.)
Re: It is strongly recommended that you plan to migrate to OSPF or EIGRP
Totally agree.
Normally, businesses I've worked at used OSPF over EIGRP as it provided more vendors to choose from and, in large networks, even sometimes helped in equipment pricing, even with Cisco, as they knew your routing protocol allow usage of brand X.
