Citrix Netscaler Fragmentation Issue

George Bonser gbonser at
Wed Jun 8 22:15:29 CEST 2011

> The native mode of netscalers is "accept the TCP connection to the
> netscaler, extract the HTTP request from it, open a new and
> TCP connection (with independent keepalives etc.) to the backend
> server, stuff the HTTP request in there".

Right, that would be how we are using it.  No connections actually get
established from the client to the server.  Client connections are
established on the Netscaler and a separate connection established to
the server.

> This is where Netscalers really excel, and how they want to be used.

Yup.  I was an early adopter of their technology long before Citrix
bought them.  But this bug is a complete show-stopper for IPv6.  The
unit goes completely deaf/mute.  It thinks everything is up, all servers
and all VIPs, but it simply stops responding to ARP on the outside
interface for all VIPs, v4 or v6.  In other words, once it gets into
this mode, the entire device stops working on the Internet side.  Very
nasty bug.

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