An important aspect of dual-stack deployment is performance. Dual-stack hosts are configured to always prefer IPv6 when a hostname resolves into both an A (IPv4 address) and an AAAA (IPv6 address) record. The deployment of dual-stack services (e.g. FTP mirror) with different performance for IPv4 and IPv6 must be avoided because the IP layer does not remain transparent. We have seen the deployment of a dual-stack FTP mirror with a poor IPv6 performance, causing all the people used to upgrade their applications on this mirror having deployed IPv6 FTP clients to get a 80kBps bandwidth instead of 4Mbps for their downloads. This issue can of course only be controlled for services one deploys oneself. For remote services the only thing one can do is to keep the reason for these problems in mind (and to educate unknown users accordingly). It is important that people know that this does not happen because IPv6 is slower in and of itself.

One further management issue in deploying an IPv6/IPv4 dual-stack network lies in configuring both internal and external routing for both protocols. If one has for example used OSPFv2 for intra site routing before, adding IPv6 to the Layer 3 network one will either make the transition to OSPFv3 or IS-IS necessary or one will at least be forced to run one of these IGPs in addition to OSPFv2.