TTL for name servers

[hugo hugoo]

Dear all,
 
Can anyone clarify to me the use of the TTL for a NS record?
Let’s take the example of a *.be domain.
 
A TTL value is present on both locations.
 
1)   
In a dns.be server (for example x.dns.be): in my example here below, value is
86400   

2)   
In the name server itself: in my example here below, value is
345600  

 
If we plan to change the name server to be used for a certain domain, do we have to change the TTL in the dns.be?
Is this possible?
 
Is this value that all the cache servers use?
If yes…what about the TTL value of the name server itself?
 
 
Thank in advance of any useful feedback,
 
Hugo,
 
 
Example:
 
 
dig @localhost google.be NS +trace
 
; <<>> DiG 9.6-ESV-R4 <<>> @localhost google.be NS +trace
; (1 server found)
;; global options: +cmd
.                       502894  IN      NS      f.root-servers.net.
.                       502894  IN      NS      g.root-servers.net.
.                       502894  IN      NS      h.root-servers.net.
.                       502894  IN      NS      a.root-servers.net.
.                       502894  IN      NS      i.root-servers.net.
.                       502894  IN      NS      b.root-servers.net.
.                       502894  IN      NS      j.root-servers.net.
.                       502894  IN      NS      c.root-servers.net.
.                       502894  IN      NS      k.root-servers.net.
.                       502894  IN      NS      l.root-servers.net.
.                       502894  IN      NS      d.root-servers.net.
.                       502894  IN      NS      m.root-servers.net.
.                       502894  IN      NS      e.root-servers.net.
;; Received 436 bytes from 127.0.0.1#53(127.0.0.1) in 0 ms
 
be.                     172800  IN      NS      m.ns.dns.be.
be.                     172800  IN      NS      x.dns.be.
be.                     172800  IN      NS      london.ns.dns.be.
be.                     172800  IN      NS      prague.ns.dns.be.
be.                     172800  IN      NS      brussels.ns.dns.be.
be.                     172800  IN      NS      amsterdam.ns.dns.be.
;; Received 307 bytes from 198.41.0.4#53(a.root-servers.net) in 27 ms
 
google.be.              86400   IN      NS      ns2.google.com.
google.be.              86400   IN      NS      ns1.google.com.
google.be.              86400   IN      NS      ns4.google.com.
google.be.              86400   IN      NS      ns3.google.com.
;; Received 109 bytes from 193.190.135.4#53(brussels.ns.dns.be) in 1 ms
 
google.be.              345600  IN      NS      ns4.google.com.
google.be.              345600  IN      NS      ns1.google.com.
google.be.              345600  IN      NS      ns3.google.com.
google.be.              345600  IN      NS      ns2.google.com.
;; Received 173 bytes from 216.239.36.10#53(ns3.google.com) in 18 ms
  		 	   		  
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