Recommended way to shutdown a working BGP session -- ordered bgp session stop -- bgp session shutdown

Francis Brosnan Blázquez francis.brosnan at aspl.es
Fri Dec 7 22:48:51 CET 2018


Hello.

We are using bird with several upstream providers, all of them with a
share of traffic.

We are in the process of shutting down one of them but we are unsure
how to proceed to minimize loss of traffic.

We have been reading and looking for general recommendations but it is
not clear (besides using graceful shutdown which is not supported by
the upstream we want to shutdown).

We have been looking at mailing list but we haven't found anything
treating this matter.

So far, solutions we have come up are:

1) Use AS-path prepend to increase metric on the uptstream to be
shutted down and once nearly no traffic comes in through that link,
shutdown
BGP and unplug. Something like:

    export filter
{                                                                                                                                                                                                                       
                                                                                                                                                                                                                                          
          if source = RTS_STATIC then { # Export only static
routes                                                                                                                                                                       
                 # Assign our
community                                                                                                                                                                                                   

bgp_community.add((65000,64501));                                                                                                                                                                                        
                 # Artificially increase path
length                                                                                                                                                                                      
                 # by advertising local AS number
twice                                                                                                                                                                                   
                 if bgp_path ~ [= 65000 =]
then                                                                                                                                                                                           
                      bgp_path.prepend(65000);
                      bgp_path.prepend(65000);

accept;                                                                                                                                                                                                                  
           }                                                                                                                                                                                                                               

reject;                                                                                                                                                                                                                         
    };                         

2) Another solution is to just shutdown BGP session but leave upstream
connected and configured (so outdated routers we still reach us...).

3) And the obvious, just shutdown BGP session and unplug the cable.

It would be great to know your opinion and what's the recommended way
to proceed. 

What do you think?

Many thanks
Best Regards.



-- 
Francis Brosnan Blázquez <francis.brosnan at aspl.es>
ASPL -- Advanced Software Production Line, S.L.
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