IP | XB Field Notes

Intended source scenario, not an observed run. Client, router and target are connected in the request direction. A crossed return line marks removal of the target return default. The client gateway stays unchanged but the HTTP attempt times out, showing why a route out still needs a route back.

A default route matches broadly; it does not rescue every failed path

An IPv4 default route is the prefix 0.0.0.0/0: it matches every IPv4 destination, with the least possible specificity. In a selected routing table, a longer matching prefix normally takes precedence. The default is not a procedure that retries whenever a more specific route fails. Routing policy selects relevant tables, and the chosen route describes a forwarding decision rather than promising that the entire round trip will succeed. ...

For the one destination 192.0.2.77, the connected /24 row selects lab0 directly, while the highlighted, more-specific /32 row wins via gateway 192.0.2.1. The rows show route specificity, not two sequential forwarding hops.

A subnet prefix shapes connected routes; the routing table chooses the path

An IPv4 prefix length says how many leading address bits identify a network. For 192.0.2.5/24, the network is 192.0.2.0/24 and the ordinary broadcast address is 192.0.2.255. Configuring that interface commonly installs a connected route, but the prefix is not the entire routing algorithm. The kernel consults routing policy and route tables to select a path for each destination. ...

A finite dynamic DHCPv4 lease has renewal and rebinding milestones before expiry. Successful renewal updates the deadlines; server-supplied valid timers can differ from the default fractions.

DHCP lends the address until it expires

Dynamic DHCPv4 allocation lends an address for a lease period. Renewal can extend that period; expiry permits reuse. DHCP also supports other allocation policies, so a finite dynamic lease is the scope of this article, not the only configuration DHCP can deliver. ...