[j-nsp] source address selection for RE generated traffic addresses to direct neighbors

Martin T m4rtntns at gmail.com
Tue Jan 22 12:18:49 EST 2019


how does Junos choose the source address for RE generated traffic
addresses to direct neighbors if the application(for example ping
utility) does not bind to specific address? Does it choose the first
address configured on the egress interface which falls in the same
network as the destination address? Looks like it because if I have a
following configuration:

root at vmx1> show configuration interfaces ge-0/0/0.0 family inet

root at vmx1> show interfaces ge-0/0/0.0 terse
Interface               Admin Link Proto    Local                 Remote
ge-0/0/0.0              up    up   inet

root at vmx1>

..and I execute the "ping", then the source address is

And for IPv6 it should be very straightforward. RFC6724 defines the
"Prefer appropriate scope" rule and as Junos seems to allow only
single link-local IPv6 address per IFL, then for locally generated
IPv6 traffic addressed to direct neighbors uses that link-local IPv6
address as a source address?


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