Source Address
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1. The IPv4 source address of the encapsulating ("outer") packet can
be spoofed.
...
... decapsulator verifies that the IPv4
source address of the packet is the same as the address of the
configured tunnel ...
... The hosts in the site originate the packets with IPv6 source
addresses coming from a well-known prefix, whereas the destination
addresses ...
... router at Site B, and Router A could verify
that the source address of the packet matches the prefix. Site B
will not be able to do a similar verification ...
... RFC3884]. This mainly affects scenario (1).
3. Source address selection depends on the notions of routes and
interfaces. This implies that the reachability ...
... interfaces (rather
than configured in SPDs) for proper source address selection.
If the IPsec tunnel mode ...
... applied to a tunnel interface. Source address spoofing can be
limited by enabling ingress filtering ...