Because a stub implies there is "no path through," while a virtual link implies "there is a path through." The two are contradictory. There is actually danger of routing loops if you could do this, since the routers in the middle of the stub area wouldn't have the information required to properly route the traffic through the stub area itself.
Think of it like iBGP without synch, and without full routing running in the cloud. Okay, that probably didn't make it any simpler. :-) Let's try this:
If B is marked as a "stub," as in a stub area, it should only have one exit. Suppose C knows of some path through A, but B doesn't know about it (or it only pays attention to it's default exit point, as a good stub should do). Now, C forwards a packet to B, and B happens to be using C as it's default exit point--a loop.
In reality, the problem is more fundamental, though--stub means "there's only one exit point from this area," while virtual link means "there's a path through this area." They are in logical conflict with one another just in defining them.
Question We run asr9001 with XR 6.1.3, and we have a very long delay to
login w/ SSH 1 or 2 to the device compare to IOS device. After
investigation, the there is 1s delay between the client KEXDH_INIT and
the server (XR) KEXDH_REPLY. After debug ssh serv...
Introduction The purpose of this document is to demonstrate the Open
Shortest Path First (OSPF) behavior when the V-bit (Virtual-link bit) is
present in a non-backbone area. The V-bit is signaled in Type-1 LSA only
if the router is the endpoint of one or ...
Hi, I am seeing quite a few issues with patch install and wanted to
share my experience and workaround to this. Login to admin via CLI, then
access root with the “shell” command Issue “df –h” and you’ll probably
see the following directory full or nearly ...