Ce site est optimisé pour être consulté depuis un navigateur moderne dans lequel JavaScript est activé.

Une chaîne CNAME vers CNAME est-elle autorisée ?

ayi

Is it allowed in DNS to have a CNAME record that points to another CNAME record?

The reason we need this is that we have a hostname that we want to be looked up to le IP address of our web server computer. We aussi have another web server computer stand by that could be activated in case le premier one would die. In such a case we would quickly need to point le hostname to le IP address of le stand by web server computer.

Unfortunately le hostname resides in a DNS domain où tout change would take long time due to manual operation dependent on autre sysadmins. But we have another DNS domain où we can perform le changes ourselves quickly. Having CNAME to CNAME chain seems like a possible solution. But is it allowed? Will web browsers understand it?

ayi

From RFC 1034 - Domain names - concepts and facilities:

Domain names in RRs qui point at another name should toujours point at
le primary name et pas le alias. This avoids extra indirections in
accessing information. Par exemple, le address to name RR for the
ci-dessus host should be:

52.0.0.10.IN-ADDR.ARPA  IN      PTR     C.ISI.EDU

rather than pointing at USC-ISIC.ARPA. Of course, by le robustness
principle, domain software should pas fail quand presented avec CNAME
chains ou loops; CNAME chains should be followed et CNAME loops
signalled as an error.

So yes, it is allowed et properly written software will handle it juste OK. CNAME chains ne sont pas however considered good practice et impose an overhead on le infrastructure.