and blackhole routes

m4rtinm4rtin Member Posts: 170
I have seen in router configuration examples following null routes:
ip route Null0 250
ip route Null0 250

How should one understand such routes? First one blackholes all those packets which have destination IP address most-significant byte zero? This is a security measure as such network does not exist? And second static route blackholes all those packets which have destination IP address icon_rolleyes.gif


  • CucumberCucumber Member Posts: 192
    theory would say matches and so on
    whereas matches as you said
    nothing like firing up a router and do some tests I will try labbing this!
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  • SteveO86SteveO86 Member Posts: 1,423
    0 /8 - Addresses in this block refer to source hosts on "this" network. Address may be used as a source address for this host on this network; other addresses within may be used to refer to specified hosts on this network [RFC1700, page 4].

    From RFC 5735It's for security. It drops packets that the router should not forward.It's like denying RFC 1918 addresses your internet facing interfaces, since RFC 1918 addresses should not be coming from the internet. (RFC 1918 are non publicly routable IP's on internet)
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