Isis configuration support

[cchoate54]

Here is the documentation to describe the initial changes proposed to introduce FRR-ISIS configuration to SONiC.

Enable isisd and add ISIS Config Support.

Repo	PR title	State
sonic-buildimage	Enable isisd and add ISIS config Support	
sonic-utilities	ISIS show command	

[zhangyanzhao]

@cchoate54 can you please add the code PRs by referring to #806 ? Thanks.

[zhangyanzhao]

community review recording https://zoom.us/rec/share/tHWVKfn1VXDl9tlYRFezxTUtTcZ4QKlt8DCz2hYuR-S2aNelacjCqmOUMicTpRo.mKL3EctOVqP1y9EB

[andriy-kokhan]

I believe that in an ideal case it would be great to have systemd service per routing protocol and also systemd target that groups these services. This could provide the best flexibility. E.g.,

routing.target
   bgp.service
   isis.service
   ospf.service

That's the way how we group SONiC services with sonic.target at the moment. With this approach we can even implement a case with the static routes only (no routing protocols) which can be applicable for the mgmt switches.

[cchoate54]

@venkatmahalingam and @dgsudharsan can you please review the changes made based on your suggestions

[zhangyanzhao]

Moved from 202305 release to 202311.

[zhangyanzhao]

@cchoate54 can you please help to double check if all comments have been addressed? We need reviewers to approve this PR if no additional comments. Thanks.

[zhangyanzhao]

no update, move to backlog

[QupinghaoNN]

@cchoate54 Can configuration be done through the CLI of sonic-utilities to write to config_db, or can it only be done through REST or gNMI in the management framework?