I seriously doubt it disables CEF - I suspect that at worst, packets for which the command is used (TCP SYNs) may not be CEF'd, but all other packets should be fine.
(Russ White may be able to speak on this further. Perhaps if I say something like "BGP OSPF EIGRP IS-IS" it will get his attention.)
The problem with making a list of exactly what is supported in the CEF path and what isn't, as nice as such a thing would be, has been that it changes all the time between IOS versions. But as CEF becomes more and more the norm and CEF-incompatible features become less common, maybe we can start to hope for a list of what features *aren't* CEF-capable at an IOS Train level of granularity (rather than on a per-release basis).
Adjusting your TCP MSS will not disable CEF--in fact, it has little to do with CEF, since CEF isn't (typically) used for locally orignated packets, and adjusting the TCP MSS is only going to impact locally originated packets. They should be able to co-exist just fine.
(I should clarify my "all other packets should be fine" comment earlier: I'd imagine the added task of checking a bit in each TCP packet's TCP header can be done in CEF mode, since policy routing has been CEF-capable for a good while now.)
Hmmm... Very interesting--it _does_ apply to the packets passing through the router, rather than packets being sent to/transmitted by the router. So, this would need to be supported in CEF for CEF to work when it's configured. But, poking around internally, I see that it is supported in CEF, and it's also supported on most if not all of the hardware platforms.
No, not really. I looked at the internal Cisco web sites, and didn't find a specific reference, but found some defects on aspects of the support for mss adjust which indicate it's supported in the CEF path. I then checked the source code, and the code is there, so I gather it is supported. I didn't test it in the lab, though.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...